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Sourcecode: firebird1.5 version File versions

vio.cpp

/*
 *    PROGRAM:    JRD Access Method
 *    MODULE:           vio.c
 *    DESCRIPTION:      Virtual IO
 *
 * The contents of this file are subject to the Interbase Public
 * License Version 1.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy
 * of the License at http://www.Inprise.com/IPL.html
 *
 * Software distributed under the License is distributed on an
 * "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express
 * or implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code was created by Inprise Corporation
 * and its predecessors. Portions created by Inprise Corporation are
 * Copyright (C) Inprise Corporation.
 *
 * All Rights Reserved.
 * Contributor(s): ______________________________________.
 *
 * 2001.07.06 Sean Leyne - Code Cleanup, removed "#ifdef READONLY_DATABASE"
 *                         conditionals, as the engine now fully supports
 *                         readonly databases.
 * 2002.08.21 Dmitry Yemanov: fixed bug with a buffer overrun,
 *                            which at least caused invalid dependencies
 *                            to be stored (DB$xxx, for example)
 * 2002.10.21 Nickolay Samofatov: Added support for explicit pessimistic locks
 * 2002.10.29 Nickolay Samofatov: Added support for savepoints
 * 2002.10.29 Sean Leyne - Removed obsolete "Netware" port
 * 2002.12.22 Alex Peshkoff: Bugcheck(291) fix for update_in_place
 *                                         of record, modified by pre_trigger
 * 2003.03.01 Nickolay Samofatov: Fixed database corruption when backing out
 *                           the savepoint after large number of DML operations 
 *                           (so transaction-level savepoint is dropped) and 
 *                                         record was updated _not_ under the savepoint and 
 *                                         deleted under savepoint. Bug affected all kinds 
 *                                         of savepoints (explicit, statement, PSQL, ...)
 * 2003.03.02 Nickolay Samofatov: Use B+ tree to store undo log
 *
 */

#include "firebird.h"
#include "../jrd/ib_stdio.h"
#include <string.h>
#include "../jrd/ibsetjmp.h"
#include "../jrd/jrd.h"
#include "../jrd/val.h"
#include "../jrd/req.h"
#include "../jrd/tra.h"
#include "gen/ids.h"
#include "../jrd/lck.h"
#include "../jrd/lls.h"
#include "../jrd/scl.h"
#include "../jrd/y_ref.h"
#include "../jrd/ibase.h"
#include "../jrd/flags.h"
#include "../jrd/ods.h"
#include "../jrd/pio.h"
#include "../jrd/btr.h"
#include "../jrd/exe.h"
#include "../jrd/rse.h"
#include "../jrd/rng.h"
#include "../jrd/thd.h"
#ifdef VIO_DEBUG
#include "../jrd/all.h"
#include "../jrd/vio_debug.h"
#endif
#include "../jrd/all_proto.h"
#include "../jrd/blb_proto.h"
#include "../jrd/cch_proto.h"
#include "../jrd/dbg_proto.h"
#include "../jrd/dfw_proto.h"
#include "../jrd/dpm_proto.h"
#include "../jrd/err_proto.h"
#include "../jrd/evl_proto.h"
#include "../jrd/gds_proto.h"
#include "../jrd/idx_proto.h"
#include "../jrd/isc_s_proto.h"
#include "../jrd/jrd_proto.h"
#include "../jrd/lck_proto.h"
#include "../jrd/met_proto.h"
#include "../jrd/mov_proto.h"
#include "../jrd/rng_proto.h"
#include "../jrd/sbm_proto.h"
#include "../jrd/sch_proto.h"
#include "../jrd/scl_proto.h"
#include "../jrd/sqz_proto.h"
#include "../jrd/thd_proto.h"
#include "../jrd/tpc_proto.h"
#include "../jrd/tra_proto.h"
#include "../jrd/vio_proto.h"

extern "C" {


static void check_class(TDBB, JRD_TRA, RPB *, RPB *, USHORT);
static void check_control(TDBB);
static BOOLEAN check_user(TDBB, DSC *);
static void delete_(TDBB, RPB *, SLONG, JrdMemoryPool *);
static UCHAR *delete_tail(TDBB, RPB *, SLONG, UCHAR *, UCHAR *);
static void expunge(TDBB, RPB *, JRD_TRA, SLONG);
static void garbage_collect(TDBB, RPB *, SLONG, LLS);
static void garbage_collect_idx(TDBB, RPB *, RPB *, REC);
#ifdef GARBAGE_THREAD
static void THREAD_ROUTINE garbage_collector(DBB);
#endif
static SAV get_free_save_point_block(JRD_TRA);
static void list_staying(TDBB, RPB *, LLS *);
#ifdef GARBAGE_THREAD
static void notify_garbage_collector(TDBB, RPB *);
#endif

#define PREPARE_OK       0
#define PREPARE_CONFLICT 1
#define PREPARE_DELETE   2
#define PREPARE_LOCKERR  3

static int prepare_update(TDBB, JRD_TRA, SLONG, RPB *, RPB *, RPB *, LLS *, BOOLEAN);

static BOOLEAN purge(TDBB, RPB *);
static REC replace_gc_record(JRD_REL, REC *, USHORT);
static void replace_record(TDBB, RPB *, LLS *, JRD_TRA);
static void set_system_flag(RPB *, USHORT, SSHORT);
static void update_in_place(TDBB, JRD_TRA, RPB *, RPB *);
static void verb_post(TDBB, JRD_TRA, RPB *, REC, RPB *, BOOLEAN, BOOLEAN);
static void RefetchRecord(TDBB tdbb, RPB * rpb, JRD_TRA transaction);

/* Pick up relation ids */

#ifndef DEV_BUILD
#define FUDGE     1
#endif
#define RELATION(name, id, ods)     id,
#define FIELD(symbol, name, id, update, ods, new_id, new_ods)
#define END_RELATION

typedef ENUM rids {
#include "../jrd/relations.h"
rel_MAX} RIDS;

#undef RELATION
#undef FIELD
#undef END_RELATION

#ifdef GARBAGE_THREAD
static const SCHAR gc_tpb[] = { isc_tpb_version1, isc_tpb_read,
      isc_tpb_read_committed, isc_tpb_rec_version,
      isc_tpb_ignore_limbo
};
#endif


SLONG VIO_savepoint_large(struct sav *savepoint, SLONG size)
{
/**************************************
 *
 *    s a v e p o i n t _ l a r g e
 *
 **************************************
 *
 * Functional description
 *    Return a measure of how big the current savepoint has gotten.
 *      The number returned is the size minus number of 'sbm' and 'bms' 
 *      structs   that are allocated.  This number does not take into account
 *        the data allocated to 'vct_undo'. Function stops counting when return
 *      value gets negative
 *
 **************************************/
      VCT verb_actions;
      SLONG count;

      count = size;
      verb_actions = savepoint->sav_verb_actions;

      while (verb_actions) {
            count -= SBM_size(&verb_actions->vct_records);
            if (count < 0)
                  break;
            verb_actions = verb_actions->vct_next;
      }

      return count;
}

void VIO_backout(TDBB tdbb, RPB * rpb, JRD_TRA transaction)
{
/**************************************
 *
 *    V I O _ b a c k o u t
 *
 **************************************
 *
 * Functional description
 *    Backout the current version of a record.  This may called
 *    either because of transaction death or because the record
 *    violated a unique index.  In either case, get rid of the
 *    current version and back an old version.
 *
 *    This routine is called with an inactive RPB, and has to
 *    take great pains to avoid conflicting with another process
 *    which is also trying to backout the same record.  On exit
 *    there is no active RPB, and the record may or may not have
 *    been backed out, depending on whether we encountered conflict.
 *    But this record is doomed, and if we don't get it somebody
 *    will.
 *
 **************************************/
      DBB dbb;
      RPB temp, temp2;
      JRD_REL relation;
      REC data, old_data, gc_rec1, gc_rec2;
      LLS going, staying;

      SET_TDBB(tdbb);
      dbb = tdbb->tdbb_database;
      CHECK_DBB(dbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES)
            ib_printf("VIO_backout (rpb %"SLONGFORMAT", transaction %"SLONGFORMAT
                          ")\n", rpb->rpb_number,
                          transaction ? transaction->tra_number : 0);
#endif

      relation = rpb->rpb_relation;
      VIO_bump_count(tdbb, DBB_backout_count, relation, false);
      going = staying = NULL;
      old_data = data = NULL;
      gc_rec1 = gc_rec2 = NULL;

/* If there is data in the record, fetch it now.  If the old version
   is a differences record, we will need it sooner.  In any case, we
   will need it eventually to clean up blobs and indices. If the record
   has changed in between, stop now before things get worse.*/

      temp = *rpb;
      if (!DPM_get(tdbb, &temp, LCK_read))
            return;

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES_INFO)
            ib_printf
                  ("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   temp.rpb_page, temp.rpb_line, temp.rpb_transaction,
                   temp.rpb_flags, temp.rpb_b_page, temp.rpb_b_line,
                   temp.rpb_f_page, temp.rpb_f_line);
      if (
            (temp.rpb_b_page != rpb->rpb_b_page
             || temp.rpb_b_line != rpb->rpb_b_line
             || temp.rpb_transaction != rpb->rpb_transaction)
            && debug_flag > DEBUG_WRITES_INFO) ib_printf("    wrong record!)\n");
#endif

      if (temp.rpb_b_page != rpb->rpb_b_page ||
            temp.rpb_b_line != rpb->rpb_b_line ||
            temp.rpb_transaction != rpb->rpb_transaction) {
            CCH_RELEASE(tdbb, &temp.rpb_window);
            return;
      }
      if ((temp.rpb_flags & rpb_deleted) && 
            !(temp.rpb_flags & rpb_delta))
            CCH_RELEASE(tdbb, &temp.rpb_window);
      else {
            temp.rpb_record = VIO_gc_record(tdbb, relation);
            VIO_data(tdbb, &temp, reinterpret_cast < blk * >(dbb->dbb_permanent));
            data = temp.rpb_prior;
            old_data = temp.rpb_record;
            rpb->rpb_prior = temp.rpb_prior;
            gc_rec2 = temp.rpb_record;
            LLS_PUSH(temp.rpb_record, &going);
      }

/* Set up an extra record parameter block.  This will be used to preserve
   the main record information while we chase fragments. */

      temp2 = temp = *rpb;

/* If there is an old version of the record, fetch it's data now. */

      if (rpb->rpb_b_page) {
            temp.rpb_record = gc_rec1 = VIO_gc_record(tdbb, relation);
            if (!DPM_get(tdbb, &temp, LCK_read))
                  goto gc_cleanup;
            if (temp.rpb_b_page != rpb->rpb_b_page ||
                  temp.rpb_b_line != rpb->rpb_b_line ||
                  temp.rpb_transaction != rpb->rpb_transaction) {
                  CCH_RELEASE(tdbb, &temp.rpb_window);
                  goto gc_cleanup;
            }
            if (temp.rpb_flags & rpb_delta)
                  temp.rpb_prior = data;
            DPM_fetch_back(tdbb, &temp, LCK_read, 1);
            if (temp.rpb_flags & rpb_deleted)
                  CCH_RELEASE(tdbb, &temp.rpb_window);
            else
                  VIO_data(tdbb, &temp,
                               reinterpret_cast < blk * >(dbb->dbb_permanent));
            gc_rec1 = temp.rpb_record;
            temp.rpb_page = rpb->rpb_b_page;
            temp.rpb_line = rpb->rpb_b_line;
      }

/* Re-fetch the record. */

      if (!DPM_get(tdbb, rpb, LCK_write))
            goto gc_cleanup;

#ifdef VIO_DEBUG
      if ((temp2.rpb_b_page != rpb->rpb_b_page ||
             temp.rpb_b_line != rpb->rpb_b_line ||
             temp.rpb_transaction != rpb->rpb_transaction)
            && debug_flag >
            DEBUG_WRITES_INFO) ib_printf("    record changed!)\n");
#endif

/* If the record is in any way suspicious, release the record and give up. */

      if (rpb->rpb_b_page != temp2.rpb_b_page ||
            rpb->rpb_b_line != temp2.rpb_b_line ||
            rpb->rpb_transaction != temp2.rpb_transaction) {
            CCH_RELEASE(tdbb, &rpb->rpb_window);
            goto gc_cleanup;
      }

/* even if the record isn't suspicious, it may have changed a little */

      temp2 = *rpb;
      rpb->rpb_undo = old_data;

      if (rpb->rpb_flags & rpb_delta)
            rpb->rpb_prior = data;

/* Handle the case of no old version simply. */

      if (!rpb->rpb_b_page) {
            delete_(tdbb, rpb, (SLONG) 0, 0);
            if (!(rpb->rpb_flags & rpb_deleted)) {
                  BLB_garbage_collect(tdbb, going, 0, rpb->rpb_page, relation);
                  IDX_garbage_collect(tdbb, rpb, going, 0);
                  LLS_POP(&going);
            }
            goto gc_cleanup;
      }

/* If both record versions are on the same page, things are a little
   simpler */

      if (rpb->rpb_page == temp.rpb_page && !rpb->rpb_prior) {
            DPM_backout(tdbb, rpb);
            if (temp2.rpb_flags & rpb_deleted)
                  goto gc_cleanup;
            delete_tail(tdbb, &temp2, rpb->rpb_page, 0, 0);
      }
      else {
            /* Bring the old version forward.  If the outgoing version was deleted,
               there is no garbage collection to be done.  */

            rpb->rpb_address = temp.rpb_address;
            rpb->rpb_length = temp.rpb_length;
            rpb->rpb_flags = temp.rpb_flags & rpb_deleted;
            if (temp.rpb_prior)
                  rpb->rpb_flags |= rpb_delta;
            rpb->rpb_b_page = temp.rpb_b_page;
            rpb->rpb_b_line = temp.rpb_b_line;
            rpb->rpb_transaction = temp.rpb_transaction;
            rpb->rpb_format_number = temp.rpb_format_number;

            if (temp2.rpb_flags & rpb_deleted) {
                  replace_record(tdbb, rpb, 0, transaction);
                  if (!DPM_fetch(tdbb, &temp, LCK_write))
                        BUGCHECK(291);    /* msg 291 cannot find record back version */
                  delete_(tdbb, &temp, rpb->rpb_page, 0);
                  goto gc_cleanup;
            }

            /* There is cleanup to be done.  Bring the old version forward first */

            rpb->rpb_flags &=
                  ~(rpb_fragment | rpb_incomplete | rpb_chained | rpb_gc_active);
            DPM_update(tdbb, rpb, 0, transaction);
            delete_tail(tdbb, &temp2, rpb->rpb_page, 0, 0);

            /* Next, delete the old copy of the now current version. */

            if (!DPM_fetch(tdbb, &temp, LCK_write))
                  BUGCHECK(291);          /* msg 291 cannot find record back version */
            delete_(tdbb, &temp, rpb->rpb_page, 0);
      }


      rpb->rpb_prior = NULL;
      list_staying(tdbb, rpb, &staying);
      BLB_garbage_collect(tdbb, going, staying, rpb->rpb_page, relation);
      IDX_garbage_collect(tdbb, rpb, going, staying);

      if (going)
            LLS_POP(&going);

      while (staying)
            delete LLS_POP(&staying);

/* Return relation garbage collect record blocks to vector. */

  gc_cleanup:
      if (gc_rec1)
            gc_rec1->rec_flags &= ~REC_gc_active;
      if (gc_rec2)
            gc_rec2->rec_flags &= ~REC_gc_active;
}


void VIO_bump_count(TDBB tdbb, USHORT count_id, JRD_REL relation, bool error)
{
/**************************************
 *
 *    V I O _ b u m p _ c o u n t
 *
 **************************************
 *
 * Functional description
 *    Bump a usage count.
 *
 **************************************/
      DBB dbb;
      VCL vector, *ptr;
      USHORT relation_id;

      SET_TDBB(tdbb);
      dbb = tdbb->tdbb_database;
      CHECK_DBB(dbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE_ALL)
            ib_printf("bump_count (count_id %d, table %d)\n", count_id,
                          relation ? relation->rel_id : 0);
#endif

#ifdef PROD_BUILD
/* The sweeper threads run in the background without
   any way to inspect these counters. For debugging
   purposes, they are maintained in the DEV_BUILD. */

      if (tdbb->tdbb_flags & TDBB_sweeper)
            return;
#endif

      relation_id = relation->rel_id;
      ptr = tdbb->tdbb_attachment->att_counts + count_id;

      vector = *ptr = vcl::newVector(*dbb->dbb_permanent, *ptr, relation_id + 1);
      ((*vector)[relation_id]) += (error) ? -1 : 1;
}


int VIO_chase_record_version(TDBB tdbb, RPB * rpb, RSB rsb, JRD_TRA transaction, 
                                           BLK pool, BOOLEAN writelock)
{
/**************************************
 *
 *    V I O _ c h a s e _ r e c o r d _ v e r s i o n
 *
 **************************************
 *
 * Functional description
 *    This is the key routine in all of JRD.  Given a record, determine
 *    what the version, if any, is appropriate for this transaction.  This
 *    is primarily done by playing with transaction numbers.  If, in the
 *    process, a record is found that requires garbage collection, by all
 *    means garbage collect it.
 *
 **************************************/
      USHORT state;
      RPB temp;
      ATT attachment;
#ifdef PC_ENGINE
      JRD_REQ request;
      IRSB impure;
#endif

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE_ALL)
            ib_printf
                  ("VIO_chase_record_version (rpb %"SLONGFORMAT", transaction %"
                   SLONGFORMAT", pool %p)\n",
                   rpb->rpb_number, transaction ? transaction->tra_number : 0,
                   pool );
      if (debug_flag > DEBUG_TRACE_ALL_INFO)
            ib_printf
                  ("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
#endif

/* Handle the fast path first.  If the record is committed, isn't deleted,
   and doesn't have an old version that is a candidate for garbage collection,
   return without further ado */

      state = TRA_snapshot_state(tdbb, transaction, rpb->rpb_transaction);

/* Reset the garbage collect active flag if the transaction state is
   in a terminal state. If committed it must have been a precommitted
   transaction that was backing out a dead record version and the
   system crashed. Clear the flag and set the state to tra_dead to
   reattempt the backout. */

      if (rpb->rpb_flags & rpb_gc_active)
            switch (state) {
            case tra_committed:
                  state = tra_dead;
                  rpb->rpb_flags &= ~rpb_gc_active;
                  break;

            case tra_dead:
                  rpb->rpb_flags &= ~rpb_gc_active;
                  break;

            default:
                  break;
            }

      if ((state == tra_committed || state == tra_us) &&
            !(rpb->rpb_flags & (rpb_deleted | rpb_damaged)) &&
            (rpb->rpb_b_page == 0 ||
             rpb->rpb_transaction >= transaction->tra_oldest_active)) return TRUE;

      attachment = transaction->tra_attachment;

/* OK, something about the record is fishy.  Loop thru versions until a
   satisfactory version is found or we run into a brick wall.  Do any
   garbage collection that seems appropriate. */

/* First, save the record indentifying information to be restored on exit */

      while (TRUE) {
#ifdef VIO_DEBUG
            if (debug_flag > DEBUG_READS_INFO)
                  ib_printf
                        ("   chase record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                         ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                         rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                         rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                         rpb->rpb_f_page, rpb->rpb_f_line);
#endif
            if (rpb->rpb_flags & rpb_damaged) {
                  CCH_RELEASE(tdbb, &rpb->rpb_window);
                  return FALSE;
            }
            if (state == tra_limbo
                  && !(transaction->tra_flags & TRA_ignore_limbo)) {
                  state = TRA_wait(tdbb, transaction, rpb->rpb_transaction, TRUE);
                  if (state == tra_active)
                        state = tra_limbo;
            }
            /* If the transaction is a read committed and chooses the no version
             * option, wait for reads also!
             */
            if ((transaction->tra_flags & TRA_read_committed) &&
                  (!(transaction->tra_flags & TRA_rec_version) || writelock)) {
                  if (state == tra_limbo) {
                        CCH_RELEASE(tdbb, &rpb->rpb_window);
                        state =
                              TRA_wait(tdbb, transaction, rpb->rpb_transaction, TRUE);

                        if (!DPM_get(tdbb, rpb, LCK_read))
                              return FALSE;

                        state =
                              TRA_snapshot_state(tdbb, transaction,
                                                         rpb->rpb_transaction);

                        /* will come back with active if lock mode is no wait */

                        if (state == tra_active) {
                              /* error if we cannot ignore limbo, else fall through
                               * to next version
                               */
                              if (!(transaction->tra_flags & TRA_ignore_limbo)) {
                                    CCH_RELEASE(tdbb, &rpb->rpb_window);
                                    ERR_post(isc_deadlock, isc_arg_gds, isc_trainlim, 0);
                              }

                              state = tra_limbo;
                        }
                  }
                  else if (state == tra_active && !(rpb->rpb_flags & rpb_gc_active)) {
                        /* A read committed, no record version transaction has to wait
                           if the record has been modified by an active transaction. But
                           it shouldn't wait if this is a transient fragmented backout
                           of a dead record version. */

                        CCH_RELEASE(tdbb, &rpb->rpb_window);
                        state =
                              TRA_wait(tdbb, transaction, rpb->rpb_transaction, TRUE);
                        if (state == tra_active)
                              ERR_post(isc_deadlock, 0);

                        /* refetch the record and try again.  The active transaction
                         * could have updated the record a second time.
                         * go back to outer loop
                         */

                        if (!DPM_get(tdbb, rpb, LCK_read))
                              return FALSE;

                        state =
                              TRA_snapshot_state(tdbb, transaction,
                                                         rpb->rpb_transaction);
                        continue;
                  }
            }

            switch (state) {
                  /* If it's dead, back it out, if possible.  Otherwise continue to
                     chase backward */

            case tra_dead:
#ifdef VIO_DEBUG
                  if (debug_flag > DEBUG_READS_INFO)
                        ib_printf
                              ("    record's transaction (%"SLONGFORMAT
                               ") is dead (my TID - %"SLONGFORMAT")\n",
                               rpb->rpb_transaction, transaction->tra_number);
#endif
#ifdef GARBAGE_THREAD
                  if (!(rpb->rpb_flags & rpb_chained) &&
                        attachment->att_flags & ATT_notify_gc) {
                        notify_garbage_collector(tdbb, rpb);
                  }

#endif
            case tra_precommitted:

                  if (attachment->att_flags & ATT_NO_CLEANUP ||
                        rpb->rpb_flags & (rpb_chained | rpb_gc_active)) {
                        if (rpb->rpb_b_page == 0) {
                              CCH_RELEASE(tdbb, &rpb->rpb_window);
                              return FALSE;
                        }
                        temp = *rpb;
                        if ((!(rpb->rpb_flags & rpb_deleted)) || 
                              (rpb->rpb_flags & rpb_delta)) {
                              VIO_data(tdbb, rpb, pool);
                              rpb->rpb_page = temp.rpb_page;
                              rpb->rpb_line = temp.rpb_line;

                              if (!(DPM_fetch(tdbb, rpb, LCK_read))) {
                                    if (!DPM_get(tdbb, rpb, LCK_read))
                                          return FALSE;
                                    break;
                              }

                              if (rpb->rpb_b_page != temp.rpb_b_page ||
                                    rpb->rpb_b_line != temp.rpb_b_line ||
                                    rpb->rpb_f_page != temp.rpb_f_page ||
                                    rpb->rpb_f_line != temp.rpb_f_line ||
                                    rpb->rpb_flags != temp.rpb_flags) {
                                    CCH_RELEASE(tdbb, &rpb->rpb_window);
                                    if (!DPM_get(tdbb, rpb, LCK_read))
                                          return FALSE;
                                    break;
                              }
                              if (temp.rpb_transaction != rpb->rpb_transaction)
                                    break;
                              if (rpb->rpb_b_page == 0) {
                                    CCH_RELEASE(tdbb, &rpb->rpb_window);
                                    return FALSE;
                              }
                              if (rpb->rpb_flags & rpb_delta)
                                    rpb->rpb_prior = rpb->rpb_record;
                        }
                        /* Fetch a back version.  If a latch timeout occurs, refetch the
                           primary version and start again.  If the primary version is
                           gone, then return 'record not found'. */
                        if (!DPM_fetch_back(tdbb, rpb, LCK_read, -1))
                              if (!DPM_get(tdbb, rpb, LCK_read))
                                    return FALSE;
                        break;
                  }

                  CCH_RELEASE(tdbb, &rpb->rpb_window);
                  VIO_backout(tdbb, rpb, transaction);
                  if (!DPM_get(tdbb, rpb, LCK_read))
                        return FALSE;
                  break;

                  /* If it's active, prepare to fetch the old version. */

            case tra_limbo:
#ifdef VIO_DEBUG
                  if (debug_flag > DEBUG_READS_INFO)
                        ib_printf
                              ("    record's transaction (%"SLONGFORMAT
                               ") is in limbo (my TID - %"SLONGFORMAT")\n",
                               rpb->rpb_transaction, transaction->tra_number);
#endif

                  if (!(transaction->tra_flags & TRA_ignore_limbo)) {
                        CCH_RELEASE(tdbb, &rpb->rpb_window);
                        ERR_post(isc_rec_in_limbo,
                                     isc_arg_number, (SLONG) rpb->rpb_transaction, 0);
                  }

            case tra_active:
#ifdef VIO_DEBUG
                  if ((debug_flag > DEBUG_READS_INFO) && (state == tra_active))
                        ib_printf
                              ("    record's transaction (%"SLONGFORMAT
                               ") is active (my TID - %"SLONGFORMAT")\n",
                               rpb->rpb_transaction, transaction->tra_number);
#endif

#ifdef PC_ENGINE
                  /* for refresh ranges, we want to know about uncommitted record versions */

                  if (rsb) {
                        request = tdbb->tdbb_request;
                        impure = (IRSB_NAV) ((UCHAR *) request + rsb->rsb_impure);
                        if (impure->irsb_flags & irsb_refresh)
                              RNG_add_uncommitted_record(rpb);
                  }
#endif

                  /* we can't use this one so if there aren't any more just stop now. */

                  if (rpb->rpb_b_page == 0) {
                        CCH_RELEASE(tdbb, &rpb->rpb_window);
                        return FALSE;
                  }
                  if (!(rpb->rpb_flags & rpb_delta)) {
                        rpb->rpb_prior = NULL;
                        /* Fetch a back version.  If a latch timeout occurs, refetch the
                           primary version and start again.  If the primary version is
                           gone, then return 'record not found'. */
                        if (!DPM_fetch_back(tdbb, rpb, LCK_read, -1))
                              if (!DPM_get(tdbb, rpb, LCK_read))
                                    return FALSE;
                        break;
                  }

                  /* oh groan, we've got to get data.  This means losing our lock and that
                     means possibly having the world change underneath us.  Specifically, the
                     primary record may change (because somebody modified or backed it out) and
                     the first record back may disappear because the primary record was backed
                     out, and now the first backup back in the primary record's place. */

                  else {
                        temp = *rpb;
                        VIO_data(tdbb, rpb, pool);
                        if (temp.rpb_flags & rpb_chained) {
                              rpb->rpb_page = temp.rpb_b_page;
                              rpb->rpb_line = temp.rpb_b_line;
                              if (!DPM_fetch(tdbb, rpb, LCK_read)) {
                                    /* Things have changed, start all over again. */
                                    if (!DPM_get(tdbb, rpb, LCK_read))
                                          return FALSE;     /* entire record disappeared */
                                    break;      /* start from the primary version again */
                              }
                        }
                        else {
                              rpb->rpb_page = temp.rpb_page;
                              rpb->rpb_line = temp.rpb_line;
                              if (!DPM_fetch(tdbb, rpb, LCK_read)) {
                                    /* Things have changed, start all over again. */
                                    if (!DPM_get(tdbb, rpb, LCK_read))
                                          return FALSE;     /* entire record disappeared */
                                    break;      /* start from the primary version again */
                              }
                              if (rpb->rpb_transaction != temp.rpb_transaction) {
                                    CCH_RELEASE(tdbb, &rpb->rpb_window);
                                    if (!DPM_get(tdbb, rpb, LCK_read))
                                          return FALSE;
                                    break;
                              }
                              if (rpb->rpb_b_page == 0) {
                                    CCH_RELEASE(tdbb, &rpb->rpb_window);
                                    return FALSE;
                              }
                              if (!(rpb->rpb_flags & rpb_delta))
                                    rpb->rpb_prior = NULL;
                              /* Fetch a back version.  If a latch timeout occurs, refetch the
                                 primary version and start again.  If the primary version is
                                 gone, then return 'record not found'. */
                              if (!DPM_fetch_back(tdbb, rpb, LCK_read, -1))
                                    if (!DPM_get(tdbb, rpb, LCK_read))
                                          return FALSE;
                        }
                  }
                  break;

            case tra_us:
#ifdef VIO_DEBUG
                  if (debug_flag > DEBUG_READS_INFO)
                        ib_printf
                              ("    record's transaction (%"SLONGFORMAT
                               ") is us (my TID - %"SLONGFORMAT")\n",
                               rpb->rpb_transaction, transaction->tra_number);

#endif

                  if (rpb->rpb_flags & rpb_deleted) {
                        CCH_RELEASE(tdbb, &rpb->rpb_window);
                        return FALSE;
                  }
                  return TRUE;

                  /* If it's committed, worry a bit about garbage collection. */

            case tra_committed:
#ifdef VIO_DEBUG
                  if (debug_flag > DEBUG_READS_INFO)
                        ib_printf
                              ("    record's transaction (%"SLONGFORMAT
                               ") is committed (my TID - %"SLONGFORMAT")\n",
                               rpb->rpb_transaction, transaction->tra_number);

#endif
                  if (rpb->rpb_flags & rpb_deleted) {
                        if (rpb->rpb_transaction < transaction->tra_oldest_active &&
                              !(attachment->att_flags & ATT_no_cleanup)) {
#ifdef GARBAGE_THREAD
                              if (attachment->att_flags & ATT_notify_gc) {
                                    notify_garbage_collector(tdbb, rpb);
                                    CCH_RELEASE(tdbb, &rpb->rpb_window);
                              }
                              else
#endif
                              {
                                    CCH_RELEASE(tdbb, &rpb->rpb_window);
                                    expunge(tdbb, rpb, transaction, (SLONG) 0);
                              }
                              return FALSE;
                        }
                        CCH_RELEASE(tdbb, &rpb->rpb_window);
                        return FALSE;
                  }

                  /* Check if no garbage collection can (should) be done.
                     It might be important not to garbage collect if the primary
                     record version is not yet committed because garbage collection
                     might interfere with the updater (prepare_update, update_in_place...).
                     That might be the reason for the rpb_chained check. */

                  if (rpb->rpb_transaction >= transaction->tra_oldest_active ||
                        rpb->rpb_b_page == 0 ||
                        rpb->rpb_flags & rpb_chained ||
                        attachment->att_flags & ATT_no_cleanup) return TRUE;

                  /* Garbage collect. */

#ifdef GARBAGE_THREAD
                  if (attachment->att_flags & ATT_notify_gc) {
                        notify_garbage_collector(tdbb, rpb);
                        return TRUE;
                  }
#endif
                  purge(tdbb, rpb);

                  /* Go back to be primary record version and chase versions all over again. */
                  if (!DPM_get(tdbb, rpb, LCK_read))
                        return FALSE;
            }

            state = TRA_snapshot_state(tdbb, transaction, rpb->rpb_transaction);

            /* Reset the garbage collect active flag if the transaction state is
               in a terminal state. If committed it must have been a precommitted
               transaction that was backing out a dead record version and the
               system crashed. Clear the flag and set the state to tra_dead to
               reattempt the backout. */

            if (!(rpb->rpb_flags & rpb_chained) && rpb->rpb_flags & rpb_gc_active)
                  switch (state) {
                  case tra_committed:
                        state = tra_dead;
                        rpb->rpb_flags &= ~rpb_gc_active;
                        break;

                  case tra_dead:
                        rpb->rpb_flags &= ~rpb_gc_active;
                        break;

                  default:
                        break;
                  }
      }
}


#ifdef PC_ENGINE
int VIO_check_if_updated(TDBB tdbb, RPB * rpb)
{
/**************************************
 *
 *    V I O _ c h e c k _ i f _ u p d a t e d
 *
 **************************************
 *
 * Functional description
 *    Check to see if the record specified in the passed
 *    rpb has been updated by an uncommitted transaction.
 *    This involves looking at the latest and greatest
 *    version of the record, checking its transaction id,
 *    then checking the TIP page to see if that transaction
 *    has been committed.
 *
 **************************************/
      JRD_TRA transaction;
      USHORT state;

      SET_TDBB(tdbb);

/* loop through till we find a real version of the record;
   one that isn't going to be garbage collected */

      transaction = tdbb->tdbb_request->req_transaction;

      while (TRUE) {
            if (!DPM_get(tdbb, rpb, LCK_read))
                  return FALSE;
            else
                  CCH_RELEASE(tdbb, &rpb->rpb_window);

            /* if the system transaction updated this record,
               it automatically is considered committed */

            if (!rpb->rpb_transaction)
                  return FALSE;

            if (rpb->rpb_transaction == transaction->tra_number)
                  return FALSE;

            /* get the state of the given transaction */

            state = TRA_get_state(tdbb, rpb->rpb_transaction);

            /* Reset the garbage collect active flag if the transaction state is
               in a terminal state. If committed it must have been a precommitted
               transaction that was backing out a dead record version and the
               system crashed. Clear the flag and set the state to tra_dead to
               reattempt the backout. */

            if (rpb->rpb_flags & rpb_gc_active)
                  switch (state) {
                  case tra_committed:
                        state = tra_dead;
                        rpb->rpb_flags &= ~rpb_gc_active;
                        break;

                  case tra_dead:
                        rpb->rpb_flags &= ~rpb_gc_active;
                        break;

                  default:
                        break;
                  }

            switch (state) {
            case tra_committed:
                  return FALSE;

            case tra_active:
                  if (!(rpb->rpb_flags & rpb_gc_active))
                        return TRUE;

            case tra_precommitted:
                  THREAD_EXIT;
                  THREAD_SLEEP(100);      /* milliseconds */
                  THREAD_ENTER;
                  break;

            case tra_limbo:
                  return TRUE;

            case tra_dead:
                  VIO_backout(tdbb, rpb, transaction);
                  break;
            }
      }
}
#endif


void VIO_data(TDBB tdbb, RPB * rpb, BLK pool)
{
/**************************************
 *
 *    V I O _ d a t a
 *
 **************************************
 *
 * Functional description
 *    Given an active record parameter block, fetch the full record.
 *
 *    This routine is called with an active RPB and exits with
 *    an INactive RPB.  Yes, Virginia, getting the data for a
 *    record means losing control of the record.  This turns out
 *    to matter a lot.
 **************************************/
      USHORT length;
      UCHAR *tail, *tail_end, differences[MAX_DIFFERENCES];

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_READS)
      {
            ib_printf("VIO_data (rpb %"SLONGFORMAT", pool %p)\n",
                              rpb->rpb_number,
                              pool);
      }
      if (debug_flag > DEBUG_READS_INFO)
      {
            ib_printf("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                         ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                         rpb->rpb_page, rpb->rpb_line,
                         rpb->rpb_transaction,
                         rpb->rpb_flags,
                         rpb->rpb_b_page, rpb->rpb_b_line,
                         rpb->rpb_f_page, rpb->rpb_f_line);
      }
#endif

/* If we're not already set up for this format version number, find
   the format block and set up the record block.  This is a performance
   optimization. */

      REC record = VIO_record(tdbb, rpb, 0, (JrdMemoryPool*) pool);
      FMT format = record->rec_format;

/* If the record is a delta version, start with data from prior record. */

      REC prior = rpb->rpb_prior;

      if (prior)
      {
            tail = differences;
            tail_end = differences + sizeof(differences);
            if (prior != record)
                  MOVE_FASTER(prior->rec_data, record->rec_data,
                                    format->fmt_length);
      }
      else
      {
            tail = record->rec_data;
            tail_end = tail + record->rec_length;
      }

/* Set up prior record point for next version */

      rpb->rpb_prior = (rpb->rpb_b_page
                                && (rpb->rpb_flags & rpb_delta)) ? record : 0;

/* Snarf data from record */

      tail =
            reinterpret_cast<UCHAR*>(
                  SQZ_decompress(reinterpret_cast<char*>(rpb->rpb_address),
                                          rpb->rpb_length,
                                          reinterpret_cast<char*>(tail),
                                          reinterpret_cast<char*>(tail_end)));

      if (rpb->rpb_flags & rpb_incomplete)
      {
            const ULONG back_page  = rpb->rpb_b_page;
            const USHORT back_line = rpb->rpb_b_line;
            while (rpb->rpb_flags & rpb_incomplete)
            {
                  DPM_fetch_fragment(tdbb, rpb, LCK_read);

                  SCHAR* pIn        = reinterpret_cast<char*>(rpb->rpb_address);
                  SCHAR* pOut       = reinterpret_cast<char*>(tail);
                  SCHAR* pOutEnd    = reinterpret_cast<char*>(tail_end);

                  SCHAR* pRet = SQZ_decompress(pIn, rpb->rpb_length, pOut, pOutEnd);
                  tail = reinterpret_cast<UCHAR*>(pRet);
            }
            rpb->rpb_b_page = back_page;
            rpb->rpb_b_line = back_line;
      }

      CCH_RELEASE(tdbb, &rpb->rpb_window);

/* If this is a delta version, apply changes */

      if (prior)
      {
            length =
                  SQZ_apply_differences(record,
                                                  reinterpret_cast<char*>(differences),
                                                  reinterpret_cast<char*>(tail));
      }
      else
      {
            length = tail - record->rec_data;
      }

      if (format->fmt_length != length)
      {
#ifdef VIO_DEBUG
          if (debug_flag > DEBUG_WRITES)
                  ib_printf ("VIO_erase (rpb %d, length %d expected %d)\n", rpb->rpb_number, 
                      length, format->fmt_length);
      
          if (debug_flag > DEBUG_WRITES_INFO)
                  ib_printf ("   record  %d:%d, rpb_trans %d, flags %d, back %d:%d, fragment %d:%d\n",
                        rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction, rpb->rpb_flags,
                      rpb->rpb_b_page, rpb->rpb_b_line, rpb->rpb_f_page, rpb->rpb_f_line);
#endif
            BUGCHECK(183);                /* msg 183 wrong record length */
      }

      rpb->rpb_address = record->rec_data;
      rpb->rpb_length = format->fmt_length;
}


void VIO_erase(TDBB tdbb, RPB * rpb, JRD_TRA transaction)
{
/**************************************
 *
 *    V I O _ e r a s e
 *
 **************************************
 *
 * Functional description
 *    Erase an existing record.
 *
 *    This routine is entered with an inactive
 *    RPB and leaves having created an erased
 *    stub. 
 *
 **************************************/
      JRD_REL relation, r2;
      JRD_PRC procedure;
      RPB temp;
      DSC desc, desc2;
      LLS stack;
      USHORT id;
      BOOLEAN same_tx = FALSE;
      TEXT relation_name[32], revokee[32], privilege[32], procedure_name[32];
      SLONG tid_fetch;
      JRD_REQ request;

      SET_TDBB(tdbb);
      request = tdbb->tdbb_request;

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES)
      {
            ib_printf("VIO_erase (rpb %"SLONGFORMAT", transaction %"SLONGFORMAT")\n",
                          rpb->rpb_number, transaction->tra_number);
      }
      if (debug_flag > DEBUG_WRITES_INFO)
      {
            ib_printf("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
      }
#endif

/* If the stream was sorted, the various fields in the rpb are
   probably junk.  Just to make sure that everything is cool,
   refetch the record. */

      if (rpb->rpb_stream_flags & RPB_s_refetch)
      {
            RefetchRecord(tdbb, rpb, transaction);
            rpb->rpb_stream_flags &= ~RPB_s_refetch;
      }

      if (rpb->rpb_transaction == transaction->tra_number)
            same_tx = TRUE;               /* deleting tx has updated/inserted this record before */

/* Special case system transaction */

      if (transaction->tra_flags & TRA_system)
      {
            VIO_backout(tdbb, rpb, transaction);
            return;
      }

      transaction->tra_flags |= TRA_write;
      relation = rpb->rpb_relation;

/* If we're about to erase a system relation, check to make sure
   everything is completely kosher. */

      if (!(transaction->tra_flags & TRA_system))
      {
            switch ((RIDS) relation->rel_id)
            {
            case rel_relations:
                  if (EVL_field(0, rpb->rpb_record, f_rel_name, &desc))
                  {
                        SCL_check_relation(&desc, SCL_delete);
                  }
                  if (EVL_field(0, rpb->rpb_record, f_rel_id, &desc2))
                  {
                        id = MOV_get_long(&desc2, 0);
                        if (id < (int) rel_MAX)
                        {
                              IBERROR(187);     /* msg 187 cannot delete system relations */
                        }
                        DFW_post_work(transaction, dfw_delete_relation, &desc, id);
                        MET_lookup_relation_id(tdbb, id, FALSE);
                  }
                  break;

            case rel_procedures:
                  if (EVL_field(0, rpb->rpb_record, f_prc_name, &desc))
                  {
                        SCL_check_procedure(&desc, SCL_delete);
                  }
                  EVL_field(0, rpb->rpb_record, f_prc_id, &desc2);
                  id = MOV_get_long(&desc2, 0);
                  DFW_post_work(transaction, dfw_delete_procedure, &desc, id);
                  MET_lookup_procedure_id(tdbb, id, FALSE, TRUE, 0);
                  break;

            case rel_exceptions:
                  EVL_field(0, rpb->rpb_record, f_prc_name, &desc);
                  DFW_post_work(transaction, dfw_delete_exception, &desc, 0);
                  break;

        case rel_gens:
            EVL_field (0, rpb->rpb_record, f_prc_name, &desc);
            DFW_post_work (transaction, dfw_delete_generator, &desc, 0);
            break;

        case rel_funs:
            EVL_field (0, rpb->rpb_record, f_prc_name, &desc);
            DFW_post_work (transaction, dfw_delete_udf, &desc, 0);
            break;

            case rel_indices:
                  EVL_field(0, rpb->rpb_record, f_idx_relation, &desc);
                  SCL_check_relation(&desc, SCL_control);
                  EVL_field(0, rpb->rpb_record, f_idx_id, &desc2);
                  if ( (id = MOV_get_long(&desc2, 0)) ) {
                        if (EVL_field(0, rpb->rpb_record, f_idx_exp_blr, &desc2))
                        {
                              DFW_post_work(transaction, dfw_delete_expression_index,
                                                  &desc, id);
                        }
                        else
                        {
                              DFW_post_work(transaction, dfw_delete_index, &desc, id);
                        }
                  }
                  break;

            case rel_rfr:
                  EVL_field(0, rpb->rpb_record, f_rfr_rname, &desc);
                  SCL_check_relation(&desc, SCL_control);
                  DFW_post_work(transaction, dfw_update_format, &desc, 0);
                  EVL_field(0, rpb->rpb_record, f_rfr_fname, &desc2);
                  MOV_get_metadata_str(&desc, relation_name, sizeof(relation_name));
                  if ( (r2 = MET_lookup_relation(tdbb, relation_name)) )
                  {
                        DFW_post_work(transaction, dfw_delete_rfr, &desc2,
                                            r2->rel_id);
                  }
                  EVL_field(0, rpb->rpb_record, f_rfr_sname, &desc2);
                  DFW_post_work(transaction, dfw_delete_global, &desc2, 0);
                  break;

            case rel_prc_prms:
                  EVL_field(0, rpb->rpb_record, f_prm_procedure, &desc);
                  SCL_check_procedure(&desc, SCL_control);
                  EVL_field(0, rpb->rpb_record, f_prm_name, &desc2);
                  MOV_get_metadata_str(&desc, procedure_name, sizeof(procedure_name));
                  if ( (procedure = MET_lookup_procedure(tdbb, procedure_name, TRUE)) )
                  {
                        DFW_post_work(transaction, dfw_delete_prm, &desc2,
                                            procedure->prc_id);
                  }
                  EVL_field(0, rpb->rpb_record, f_prm_sname, &desc2);
                  DFW_post_work(transaction, dfw_delete_global, &desc2, 0);
                  break;

            case rel_fields:
                  check_control(tdbb);
                  EVL_field(0, rpb->rpb_record, f_fld_name, &desc);
                  DFW_post_work(transaction, dfw_delete_field, &desc, 0);
                  MET_change_fields(tdbb, transaction, &desc);
                  break;

            case rel_files:
                  EVL_field(0, rpb->rpb_record, f_file_name, &desc);
                  if (EVL_field(0, rpb->rpb_record, f_file_shad_num, &desc2) &&
                        (id = MOV_get_long(&desc2, 0)))
                  {
                        DFW_post_work(transaction, dfw_delete_shadow, &desc, id);
                  }
                  break;

            case rel_classes:
                  EVL_field(0, rpb->rpb_record, f_cls_class, &desc);
                  DFW_post_work(transaction, dfw_compute_security, &desc, 0);
                  break;

            case rel_triggers:
                  EVL_field(0, rpb->rpb_record, f_trg_rname, &desc);

                  /* check if this  request go through without checking permissions */
                  if (!(request->req_flags & req_ignore_perm)) {
                        SCL_check_relation(&desc, SCL_control);
                  }

                  EVL_field(0, rpb->rpb_record, f_trg_rname, &desc);
                  DFW_post_work(transaction, dfw_update_format, &desc, 0);
                  EVL_field(0, rpb->rpb_record, f_trg_name, &desc);
                  DFW_post_work(transaction, dfw_delete_trigger, &desc, 0);
                  break;

            case rel_priv:
                  EVL_field(0, rpb->rpb_record, f_file_name, &desc);
                  if (!(tdbb->tdbb_request->req_flags & req_internal))
                  {
                        EVL_field(0, rpb->rpb_record, f_prv_grantor, &desc);
                        if (!check_user(tdbb, &desc))
                        {
                              ERR_post(isc_no_priv, isc_arg_string, "REVOKE",
                                           isc_arg_string, "TABLE", isc_arg_string,
                                           "RDB$USER_PRIVILEGES", 0);
                        }
                  }
                  EVL_field(0, rpb->rpb_record, f_prv_rname, &desc);
                  EVL_field(0, rpb->rpb_record, f_prv_o_type, &desc2);
                  id = MOV_get_long(&desc2, 0);
                  DFW_post_work(transaction, dfw_grant, &desc, id);
                  break;

            case rel_log:
                  DFW_post_work(transaction, dfw_delete_log, 0, 0);
                  break;
                default:    /* Shut up compiler warnings */
                        break;
            }
      }

/* If the page can be updated simply, we can skip the remaining crud */

      temp.rpb_transaction = transaction->tra_number;
      temp.rpb_address = NULL;
      temp.rpb_length = 0;
      temp.rpb_flags = rpb_deleted;
      temp.rpb_format_number = rpb->rpb_format_number;
      temp.rpb_window.win_flags = WIN_secondary;

      tid_fetch = rpb->rpb_transaction;
      if (DPM_chain(tdbb, rpb, &temp))
      {
            rpb->rpb_b_page = temp.rpb_b_page;
            rpb->rpb_b_line = temp.rpb_b_line;
            rpb->rpb_flags |= rpb_deleted;
#ifdef VIO_DEBUG
            if (debug_flag > DEBUG_WRITES_INFO)
            {
                  ib_printf("   VIO_erase: successfully chained\n");
            }
#endif
      }
      else
      {
            /* Update stub didn't find one page -- do a long, hard update */
            stack = NULL;
            if (prepare_update(tdbb, transaction, tid_fetch, rpb, &temp, 0, &stack, FALSE))
                  ERR_post(isc_deadlock, isc_arg_gds, isc_update_conflict, 0);

            /* Old record was restored and re-fetched for write.  Now replace it.  */

            rpb->rpb_transaction = transaction->tra_number;
            rpb->rpb_b_page = temp.rpb_page;
            rpb->rpb_b_line = temp.rpb_line;
            rpb->rpb_address = NULL;
            rpb->rpb_length = 0;
            rpb->rpb_flags |= rpb_deleted;
            rpb->rpb_flags &= ~rpb_delta;

            replace_record(tdbb, rpb, &stack, transaction);
      }

/* Check to see if recursive revoke needs to be propogated */

      if ((RIDS) relation->rel_id == rel_priv)
      {
            EVL_field(0, rpb->rpb_record, f_prv_rname, &desc);
            MOV_get_metadata_str(&desc, relation_name, sizeof(relation_name));
            EVL_field(0, rpb->rpb_record, f_prv_grant, &desc2);
            if (MOV_get_long(&desc2, 0))
            {
                  EVL_field(0, rpb->rpb_record, f_prv_user, &desc2);
                  MOV_get_metadata_str(&desc2, revokee, sizeof(revokee));
                  EVL_field(0, rpb->rpb_record, f_prv_priv, &desc2);
                  MOV_get_metadata_str(&desc2, privilege, sizeof(privilege));
                  MET_revoke(tdbb, transaction, relation_name, revokee, privilege);
            }
      }
      if (!(transaction->tra_flags & TRA_system) &&
            (transaction->tra_save_point) &&
            (transaction->tra_save_point->sav_verb_count))
      {
            verb_post(tdbb, transaction, rpb, 0, 0, same_tx, FALSE);
      }

      VIO_bump_count(tdbb, DBB_delete_count, relation, false);

/* for an autocommit transaction, mark a commit as necessary */

      if (transaction->tra_flags & TRA_autocommit)
      {
            transaction->tra_flags |= TRA_perform_autocommit;
      }
      
}


#ifdef GARBAGE_THREAD
void VIO_fini(TDBB tdbb)
{
/**************************************
 *
 *    V I O _ f i n i
 *
 **************************************
 *
 * Functional description
 *    Shutdown the garbage collector thread.
 *
 **************************************/
      DBB dbb;
      SLONG count;

      dbb = tdbb->tdbb_database;

      if (dbb->dbb_flags & DBB_garbage_collector)
      {
            EVENT gc_event_fini = dbb->dbb_gc_event_fini;
            /* initialize finalization event */
            ISC_event_init(gc_event_fini, 0, 0);
            count = ISC_event_clear(gc_event_fini);

            dbb->dbb_flags &= ~DBB_garbage_collector;
            ISC_event_post(dbb->dbb_gc_event); /* Wake up running thread */
            THREAD_EXIT;
            (void) ISC_event_wait(1, &gc_event_fini, &count, 0, (FPTR_VOID) 0, 0);
            THREAD_ENTER;
            /* Cleanup finalization event */
            ISC_event_fini(gc_event_fini);
      }
}
#endif


int VIO_garbage_collect(TDBB tdbb, RPB * rpb, JRD_TRA transaction)
{
/**************************************
 *
 *    V I O _ g a r b a g e _ c o l l e c t
 *
 **************************************
 *
 * Functional description
 *    Do any garbage collection appropriate to the current
 *    record.  This is called during index creation to avoid
 *    unnecessary work as well as false duplicate records.
 *
 *    If the record complete goes away, return FALSE.
 *
 **************************************/
      USHORT state;

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE)
      {
            ib_printf("VIO_garbage_collect (rpb %"SLONGFORMAT", transaction %"
                          SLONGFORMAT")\n",
                          rpb->rpb_number, transaction ? transaction->tra_number : 0);
      }
      if (debug_flag > DEBUG_TRACE_INFO)
      {
            ib_printf("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
      }
#endif

      if (transaction->tra_attachment->att_flags & ATT_no_cleanup)
            return TRUE;

      while (TRUE)
      {
            if (rpb->rpb_flags & rpb_damaged)
            {
                  CCH_RELEASE(tdbb, &rpb->rpb_window);
                  return FALSE;
            }

            state = TRA_snapshot_state(tdbb, transaction, rpb->rpb_transaction);

            /* Reset the garbage collect active flag if the transaction state is
               in a terminal state. If committed it must have been a precommitted
               transaction that was backing out a dead record version and the
               system crashed. Clear the flag and set the state to tra_dead to
               reattempt the backout. */

            if (rpb->rpb_flags & rpb_gc_active)
            {
                  switch (state)
                  {
                  case tra_committed:
                        state = tra_dead;
                        rpb->rpb_flags &= ~rpb_gc_active;
                        break;

                  case tra_dead:
                        rpb->rpb_flags &= ~rpb_gc_active;
                        break;

                  default:
                        break;
                  }
            }

            if (state == tra_dead)
            {
                  CCH_RELEASE(tdbb, &rpb->rpb_window);
                  VIO_backout(tdbb, rpb, transaction);
            }
            else
            {
                  if (rpb->rpb_flags & rpb_deleted)
                  {
                        if (rpb->rpb_transaction >= transaction->tra_oldest_active)
                        {
                              return TRUE;
                        }
                        else
                        {
                              CCH_RELEASE(tdbb, &rpb->rpb_window);
                              expunge(tdbb, rpb, transaction, (SLONG) 0);
                              return FALSE;
                        }
                  }

                  if (rpb->rpb_transaction >= transaction->tra_oldest_active ||
                        rpb->rpb_b_page == 0)
                  {
                        return TRUE;
                  }

                  purge(tdbb, rpb);
            }

            if (!DPM_get(tdbb, rpb, LCK_read)) {
                  return FALSE;
            }
      }
}


REC VIO_gc_record(TDBB tdbb, JRD_REL relation)
{
/**************************************
 *
 *    V I O _ g c _ r e c o r d
 *
 **************************************
 *
 * Functional description
 *    Allocate from a relation's vector of garbage
 *    collect record blocks. Their scope is strictly
 *    limited to temporary usage and should never be
 *    copied to permanent record parameter blocks.
 *
 **************************************/
      DBB dbb;
      VEC vector;
      REC record;
      vec::iterator rec_ptr, end;
      RPB rpb;
      USHORT slot;

      SET_TDBB(tdbb);
      dbb = tdbb->tdbb_database;
      CHECK_DBB(dbb);

/* This will require mutex synchronization for pre-emptive multithreading. */

/* V4_MUTEX_LOCK (&relation->rel_mutex); */

/* Allocate a vector of garbage collect record blocks for relation. */

      if (!(vector = relation->rel_gc_rec)) {
            vector = relation->rel_gc_rec = vec::newVector(*dbb->dbb_permanent, 1);
      }

/* Set the active flag on an inactive garbage collect record block
   and return it. */

      for (rec_ptr = vector->begin(), end =
             vector->end(); rec_ptr != end; ++rec_ptr)
            if ((record = *(REC*) &*rec_ptr) && !(record->rec_flags & REC_gc_active)) {
            //          if ((record = *(REC*) &*rec_ptr) && !(record->rec_flags & REC_gc_active)) {
                  record->rec_flags |= REC_gc_active;
/*    V4_MUTEX_UNLOCK (&relation->rel_mutex); */
                  return record;
            }

/* Allocate a garbage collect record block if all are active. */

      rpb.rpb_record = 0;
      record =
            VIO_record(tdbb, &rpb, MET_current(tdbb, relation),
                           dbb->dbb_permanent);
      record->rec_flags |= REC_gc_active;

/* Insert the new record block into the last slot of the vector. */

      slot = vector->count() - 1;
      if ((*vector)[slot])
            vector->resize((++slot) + 1);
      (*vector)[slot] = (BLK) record;

/* V4_MUTEX_UNLOCK (&relation->rel_mutex); */
      return record;
}


int VIO_get(TDBB tdbb, RPB * rpb, RSB rsb, JRD_TRA transaction, BLK pool)
{
/**************************************
 *
 *    V I O _ g e t
 *
 **************************************
 *
 * Functional description
 *    Get a specific record from a relation.
 *
 **************************************/
      USHORT lock_type;

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_READS)
            ib_printf("VIO_get (rpb %"SLONGFORMAT", transaction %"SLONGFORMAT
                          ", pool %p)\n",
                          rpb->rpb_number, transaction ? transaction->tra_number : 0,
                          pool);
#endif

/* Fetch data page from a modify/erase input stream with a write
   lock. This saves an upward conversion to a write lock when
   refetching the page in the context of the output stream. */

      lock_type = (rpb->rpb_stream_flags & RPB_s_update) ? LCK_write : LCK_read;

      if (!DPM_get(tdbb, rpb, lock_type) ||
            !VIO_chase_record_version(tdbb, rpb, rsb, transaction, pool, FALSE))
            return FALSE;

#ifdef PC_ENGINE
      if (rsb && rsb->rsb_flags & rsb_stream_type)
            RNG_add_page(rpb->rpb_page);
#endif

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_READS_INFO)
            ib_printf
                  ("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
#endif
      if (pool)
            VIO_data(tdbb, rpb, pool);

      VIO_bump_count(tdbb, DBB_read_idx_count, rpb->rpb_relation, false);

      return TRUE;
}


int VIO_get_current(
                              TDBB tdbb,
                              RPB * rpb, JRD_TRA transaction, BLK pool, USHORT foreign_key)
{
/**************************************
 *
 *    V I O _ g e t _ c u r r e n t
 *
 **************************************
 *
 * Functional description
 *    Get the current (most recent) version of a record.  This is
 *    called by IDX to determine whether a unique index has been
 *    duplicated.  If the target record's transaction is active,
 *    wait for it.  If the record is deleted or disappeared, return
 *    FALSE.  If the record is committed, return TRUE.
 *    If foreign_key is true, we are checking for a foreign key,
 *    looking to see if a primary key/unique key exists.  For a
 *    no wait transaction, if state of transaction inserting primary key
 *    record is tra_active, we should not see the uncommitted record
 *
 **************************************/
      USHORT state;
      SLONG tid_fetch;

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE)
            ib_printf("VIO_get_current (rpb %"SLONGFORMAT", transaction %"
                          SLONGFORMAT", pool %p)\n",
                          rpb->rpb_number, transaction ? transaction->tra_number : 0,
                          pool );
#endif

      while (TRUE) {
            /* If the record doesn't exist, no problem. */

            if (!DPM_get(tdbb, rpb, LCK_read))
                  return FALSE;

#ifdef VIO_DEBUG
            if (debug_flag > DEBUG_TRACE_INFO)
                  ib_printf
                        ("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                         ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                         rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                         rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                         rpb->rpb_f_page, rpb->rpb_f_line);
#endif

            /* Get data if there is data. */

            if (rpb->rpb_flags & rpb_deleted)
                  CCH_RELEASE(tdbb, &rpb->rpb_window);
            else
                  VIO_data(tdbb, rpb, pool);

            /* If we deleted the record, everything's fine, otherwise
               the record must be considered real. */

            if (rpb->rpb_transaction == transaction->tra_number)
                  break;

            /* check the state of transaction  - tra_us is taken care of above
             * For now check the state in the tip_cache or tip bitmap. If
             * record is committed (most cases), this will be faster.
             */

            if (transaction->tra_flags & TRA_read_committed)
                  state = TPC_cache_state(tdbb, rpb->rpb_transaction);
            else
                  state =
                        TRA_snapshot_state(tdbb, transaction, rpb->rpb_transaction);

            /* Reset the garbage collect active flag if the transaction state is
               in a terminal state. If committed it must have been a precommitted
               transaction that was backing out a dead record version and the
               system crashed. Clear the flag and set the state to tra_dead to
               reattempt the backout. */

            if (rpb->rpb_flags & rpb_gc_active)
                  switch (state) {
                  case tra_committed:
                        state = tra_dead;
                        rpb->rpb_flags &= ~rpb_gc_active;
                        break;

                  case tra_dead:
                        rpb->rpb_flags &= ~rpb_gc_active;
                        break;

                  default:
                        break;
                  }

            if (state == tra_committed)
                  return ((rpb->rpb_flags & rpb_deleted) ? FALSE : TRUE);
            else if (state == tra_dead) {
                  if (transaction->tra_attachment->att_flags & ATT_no_cleanup)
                        return (foreign_key ? FALSE : TRUE);

                  VIO_backout(tdbb, rpb, transaction);
                  continue;
            }
            else if (state == tra_precommitted) {
                  THREAD_EXIT;
                  THREAD_SLEEP(100);      /* milliseconds */
                  THREAD_ENTER;
                  continue;
            }

            /* The record belongs to somebody else.  Wait for him to
               commit, rollback, or die. */

            tid_fetch = rpb->rpb_transaction;

            /* Wait as long as it takes for an active transaction which has modified
               the record. If an active transaction has used its TID to safely
               backout a fragmented dead record version, spin wait because it will
               finish shortly. */

            if (!(rpb->rpb_flags & rpb_gc_active))
                  state = TRA_wait(tdbb, transaction, rpb->rpb_transaction, TRUE);
            else {
                  BOOLEAN wait_flag;

                  wait_flag = (transaction->tra_flags & TRA_nowait) ? FALSE : TRUE;
                  transaction->tra_flags |= TRA_nowait;
                  state = TRA_wait(tdbb, transaction, rpb->rpb_transaction, TRUE);
                  if (wait_flag)
                        transaction->tra_flags &= ~TRA_nowait;

                  if (state == tra_active) {
                        THREAD_EXIT;
                        THREAD_SLEEP(100);      /* milliseconds */
                        THREAD_ENTER;
                        continue;
                  }
            }

            switch (state) {
            case tra_committed:
                  /* If the record doesn't exist anymore, no problem. This
                   * can happen in two cases.  The transaction that inserted
                   * the record deleted it or the transaction rolled back and
                   * removed the records it modified and marked itself
                   * committed
                   */

                  if (!DPM_get(tdbb, rpb, LCK_read))
                        return FALSE;

                  /* if the transaction actually rolled back and what
                   * we are reading is another record (newly inserted),
                   * loop back and try again.
                   */

                  if (tid_fetch != rpb->rpb_transaction) {
                        CCH_RELEASE(tdbb, &rpb->rpb_window);
                        continue;
                  }

                  /* Get latest data if there is data. */

                  if (rpb->rpb_flags & rpb_deleted) {
                        CCH_RELEASE(tdbb, &rpb->rpb_window);
                        return FALSE;
                  }

                  VIO_data(tdbb, rpb, pool);
                  return TRUE;

            case tra_active:
                  return (foreign_key ? FALSE : TRUE);

            case tra_dead:
                  if (transaction->tra_attachment->att_flags & ATT_no_cleanup)
                        return (foreign_key ? FALSE : TRUE);

                  VIO_backout(tdbb, rpb, transaction);
                  break;

            default:
                  BUGCHECK(184);          /* limbo impossible */
            }
      }

      return (rpb->rpb_flags & rpb_deleted) ? FALSE : TRUE;
}


#ifdef GARBAGE_THREAD
void VIO_init(TDBB tdbb)
{
/**************************************
 *
 *    V I O _ i n i t
 *
 **************************************
 *
 * Functional description
 *    Activate the garbage collector thread.
 *
 **************************************/
      DBB dbb;
      ATT attachment;
      SLONG count;

      dbb = tdbb->tdbb_database;
      attachment = tdbb->tdbb_attachment;

      if (dbb->dbb_flags & DBB_read_only) {
            return;
      }

/* If there's no presence of a garbage collector running
   then start one up. */

      if (!(dbb->dbb_flags & DBB_garbage_collector)) {
            EVENT gc_event_init = dbb->dbb_gc_event_init;
            /* Initialize initialization event */
            ISC_event_init(gc_event_init, 0, 0);
            count = ISC_event_clear(gc_event_init);

            if (gds__thread_start
                  (reinterpret_cast < FPTR_INT_VOID_PTR > (garbage_collector), dbb,
                  THREAD_medium, 0, 0)) {
                  ERR_bugcheck_msg("cannot start thread");
            }
            THREAD_EXIT;
            (void) ISC_event_wait(1, &gc_event_init, &count, 10 * 1000000, (FPTR_VOID) 0, 0);
            THREAD_ENTER;
            /* Clean up initialization event */
            ISC_event_fini(gc_event_init);
      }

/* Database backups and sweeps perform their own garbage collection
   unless passing a no garbage collect switch which means don't
   notify the garbage collector to garbage collect. Every other
   attachment notifies the garbage collector to do their dirty work. */

      if (dbb->dbb_flags & DBB_garbage_collector &&
            !(attachment->att_flags & (ATT_no_cleanup | ATT_gbak_attachment))) {
            if (dbb->dbb_flags & DBB_suspend_bgio) {
                  attachment->att_flags |= ATT_disable_notify_gc;
            }
            else {
                  attachment->att_flags |= ATT_notify_gc;
            }
      }
}
#endif

static void RefetchRecord(TDBB tdbb, RPB * rpb, JRD_TRA transaction)
{
/**************************************
 *
 *    R e f e t c h R e c o r d
 *
 **************************************
 *
 * Functional description
 *    Refetch & release the record, if we unsure,
 *  whether information about it is still valid.
 *
 **************************************/
      SLONG tid_fetch = rpb->rpb_transaction;
      if ((!DPM_get(tdbb, rpb, LCK_read)) ||
              (!VIO_chase_record_version
                  (tdbb, rpb, NULL, transaction,
                  reinterpret_cast < blk * >(tdbb->tdbb_default), 
                  FALSE))) {
            ERR_post(isc_deadlock, isc_arg_gds, isc_update_conflict, 0);
      }
      VIO_data(tdbb, rpb,
                  reinterpret_cast < blk * >(tdbb->tdbb_request->req_pool));

      /* If record is present, and the transaction is read committed,
       * make sure the record has not been updated.  Also, punt after
       * VIO_data () call which will release the page.
       */
      if ((transaction->tra_flags & TRA_read_committed) &&
            (tid_fetch != rpb->rpb_transaction) &&
            // added to check that it was not current transcation,
            // who modified the record. Alex P, 18-Jun-03
            (rpb->rpb_transaction != transaction->tra_number)) {
            ERR_post(isc_deadlock, isc_arg_gds, isc_update_conflict, 0);
      }
}

void VIO_modify(TDBB tdbb, RPB * org_rpb, RPB * new_rpb, JRD_TRA transaction)
{
/**************************************
 *
 *    V I O _ m o d i f y
 *
 **************************************
 *
 * Functional description
 *    Modify an existing record.
 *
 **************************************/
      JRD_REL relation;
      RPB temp;
      DSC desc1, desc2;
      LLS stack;
      USHORT id;

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES)
            ib_printf("VIO_modify (org_rpb %"SLONGFORMAT", new_rpb %"SLONGFORMAT
                          ", transaction %"SLONGFORMAT")\n",
                          org_rpb->rpb_number, new_rpb->rpb_number,
                          transaction ? transaction->tra_number : 0);
      if (debug_flag > DEBUG_WRITES_INFO)
            ib_printf
                  ("   old record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   org_rpb->rpb_page, org_rpb->rpb_line, org_rpb->rpb_transaction,
                   org_rpb->rpb_flags, org_rpb->rpb_b_page, org_rpb->rpb_b_line,
                   org_rpb->rpb_f_page, org_rpb->rpb_f_line);
#endif

      transaction->tra_flags |= TRA_write;
      new_rpb->rpb_transaction = transaction->tra_number;
      new_rpb->rpb_flags = 0;
      new_rpb->rpb_window.win_flags = WIN_secondary;

/* If the stream was sorted, the various fields in the rpb are
   probably junk.  Just to make sure that everything is cool,
   refetch and release the record. */

      if (org_rpb->rpb_stream_flags & RPB_s_refetch) {
            RefetchRecord(tdbb, org_rpb, transaction);
            org_rpb->rpb_stream_flags &= ~RPB_s_refetch;
      }

/* If we're the system transaction, modify stuff in place.  This saves
   endless grief on cleanup */

      relation = org_rpb->rpb_relation;
      VIO_bump_count(tdbb, DBB_update_count, relation, false);

      if (transaction->tra_flags & TRA_system) {
            update_in_place(tdbb, transaction, org_rpb, new_rpb);
            return;
      }

/* If we're about to modify a system relation, check to make sure
   everything is completely kosher. */

      if (!(transaction->tra_flags & TRA_system))
            switch ((RIDS) relation->rel_id) {
            case rel_database:
                  check_class(tdbb, transaction, org_rpb, new_rpb, f_dat_class);
                  break;

            case rel_relations:
                  EVL_field(0, org_rpb->rpb_record, f_rel_name, &desc1);
                  SCL_check_relation(&desc1, SCL_protect);
                  check_class(tdbb, transaction, org_rpb, new_rpb, f_rel_class);
                  DFW_post_work(transaction, dfw_update_format, &desc1, 0);
                  break;

            case rel_procedures:
                  EVL_field(0, org_rpb->rpb_record, f_prc_name, &desc1);
                  SCL_check_procedure(&desc1, SCL_protect);
                  check_class(tdbb, transaction, org_rpb, new_rpb, f_prc_class);
                  EVL_field(0, org_rpb->rpb_record, f_prc_id, &desc2);
                  id = MOV_get_long(&desc2, 0);
                  DFW_post_work(transaction, dfw_modify_procedure, &desc1, id);
                  break;

            case rel_rfr:
                  EVL_field(0, org_rpb->rpb_record, f_rfr_rname, &desc1);
                  SCL_check_relation(&desc1, SCL_control);
                  DFW_post_work(transaction, dfw_update_format, &desc1, 0);
                  EVL_field(0, new_rpb->rpb_record, f_rfr_rname, &desc2);
                  SCL_check_relation(&desc2, SCL_control);
                  DFW_post_work(transaction, dfw_update_format, &desc2, 0);
                  check_class(tdbb, transaction, org_rpb, new_rpb, f_rfr_class);
                  break;

            case rel_fields:
                  check_control(tdbb);
                  EVL_field(0, org_rpb->rpb_record, f_fld_name, &desc1);
                  MET_change_fields(tdbb, transaction, &desc1);
                  EVL_field(0, new_rpb->rpb_record, f_fld_name, &desc2);
                  MET_change_fields(tdbb, transaction, &desc2);
                  break;

            case rel_classes:
                  EVL_field(0, org_rpb->rpb_record, f_cls_class, &desc1);
                  DFW_post_work(transaction, dfw_compute_security, &desc1, 0);
                  EVL_field(0, new_rpb->rpb_record, f_cls_class, &desc1);
                  DFW_post_work(transaction, dfw_compute_security, &desc1, 0);
                  break;

            case rel_indices:
                  EVL_field(0, new_rpb->rpb_record, f_idx_relation, &desc1);
                  SCL_check_relation(&desc1, SCL_control);
                  EVL_field(0, new_rpb->rpb_record, f_idx_name, &desc1);
                  if (EVL_field(0, new_rpb->rpb_record, f_idx_exp_blr, &desc2))
                        DFW_post_work(transaction, dfw_create_expression_index,
                                            &desc1, tdbb->tdbb_database->dbb_max_idx);
                  else
                        DFW_post_work(transaction, dfw_create_index, &desc1, 
                                            tdbb->tdbb_database->dbb_max_idx);
                  break;

            case rel_triggers:
                  EVL_field(0, new_rpb->rpb_record, f_trg_rname, &desc1);
                  SCL_check_relation(&desc1, SCL_control);
                  EVL_field(0, new_rpb->rpb_record, f_trg_rname, &desc1);
                  DFW_post_work(transaction, dfw_update_format, &desc1, 0);
                  EVL_field(0, org_rpb->rpb_record, f_trg_rname, &desc1);
                  DFW_post_work(transaction, dfw_update_format, &desc1, 0);
                  EVL_field(0, org_rpb->rpb_record, f_trg_name, &desc1);
                  DFW_post_work(transaction, dfw_modify_trigger, &desc1, 0);
                  break;

            default:
                  break;
            }

/* We're almost ready to go.  To modify the record, we must first
   make a copy of the old record someplace else.  Then we must re-fetch
   the record (for write) and verify that it is legal for us to
   modify it -- that it was written by a transaction that was committed
   when we started.  If not, the transaction that wrote the record
   is either active, dead, or in limbo.  If the transaction is active,
   wait for it to finish.  If it commits, we can't procede and must
   return an update conflict.  If the transaction is dead, back out the
   old version of the record and try again.  If in limbo, punt.  */

      if (org_rpb->rpb_transaction == transaction->tra_number &&
            org_rpb->rpb_format_number == new_rpb->rpb_format_number) {
            update_in_place(tdbb, transaction, org_rpb, new_rpb);
            if (!(transaction->tra_flags & TRA_system) &&
                  (transaction->tra_save_point) &&
                  (transaction->tra_save_point->sav_verb_count))
                        verb_post(tdbb, transaction, org_rpb, org_rpb->rpb_undo,
                                      new_rpb, FALSE, FALSE);
            return;
      }

      stack = NULL;
      if (prepare_update(tdbb, transaction, org_rpb->rpb_transaction, org_rpb,
                           &temp, new_rpb, &stack, FALSE))
            ERR_post(isc_deadlock, isc_arg_gds, isc_update_conflict, 0);

/* Old record was restored and re-fetched for write.  Now replace it.  */

      org_rpb->rpb_transaction = new_rpb->rpb_transaction;
      org_rpb->rpb_format_number = new_rpb->rpb_format_number;
      org_rpb->rpb_b_page = temp.rpb_page;
      org_rpb->rpb_b_line = temp.rpb_line;
      org_rpb->rpb_address = new_rpb->rpb_address;
      org_rpb->rpb_length = new_rpb->rpb_length;
      org_rpb->rpb_flags &= ~rpb_delta;
      org_rpb->rpb_flags |= new_rpb->rpb_flags & rpb_delta;

      replace_record(tdbb, org_rpb, &stack, transaction);

      if (!(transaction->tra_flags & TRA_system) &&
            (transaction->tra_save_point) &&
            (transaction->tra_save_point->sav_verb_count))
                  verb_post(tdbb, transaction, org_rpb, 0, 0, FALSE, FALSE);

/* for an autocommit transaction, mark a commit as necessary */

      if (transaction->tra_flags & TRA_autocommit)
            transaction->tra_flags |= TRA_perform_autocommit;
}


BOOLEAN VIO_writelock(TDBB tdbb, RPB * org_rpb, RSB rsb, JRD_TRA transaction)
{
/**************************************
 *
 *    V I O _ w r i t e l o c k
 *
 **************************************
 *
 * Functional description
 *    Modify record to make record owned by this transaction
 *
 **************************************/
      JRD_REL relation;
      RPB temp;
      LLS stack;
      SLONG tid_fetch;

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES)
            ib_printf("VIO_writelock (org_rpb %"SLONGFORMAT", transaction %"
                          SLONGFORMAT")\n",
                          org_rpb->rpb_number, transaction ? transaction->tra_number : 0);
      if (debug_flag > DEBUG_WRITES_INFO)
            ib_printf
                  ("   old record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   org_rpb->rpb_page, org_rpb->rpb_line, org_rpb->rpb_transaction,
                   org_rpb->rpb_flags, org_rpb->rpb_b_page, org_rpb->rpb_b_line,
                   org_rpb->rpb_f_page, org_rpb->rpb_f_line);
#endif

      if (transaction->tra_flags & TRA_system) {
            // Explicit locks are not needed in system transactions
            return TRUE;
      }
      
      transaction->tra_flags |= TRA_write;
      
      REC org_record;
      if (!(org_record = org_rpb->rpb_record)) {
            org_record =
                  VIO_record(tdbb, org_rpb, NULL, tdbb->tdbb_default);
            org_rpb->rpb_address = org_record->rec_data;
            org_rpb->rpb_length = org_record->rec_format->fmt_length;
            org_rpb->rpb_format_number = org_record->rec_format->fmt_version;
      }

    // Repeat as many times as underlying record modifies
      while(TRUE) {

            /* Refetch and release the record if it is needed */
            if (org_rpb->rpb_stream_flags & RPB_s_refetch) {
                  tid_fetch = org_rpb->rpb_transaction;
                  if ((!DPM_get(tdbb, org_rpb, LCK_read)) ||
                        (!VIO_chase_record_version
                         (tdbb, org_rpb, NULL, transaction,
                          reinterpret_cast <
                          blk * >(tdbb->tdbb_default),TRUE)))
                  {
                        return FALSE;
                  }
                  VIO_data(tdbb, org_rpb,
                               reinterpret_cast < blk * >(tdbb->tdbb_request->req_pool));

                  org_rpb->rpb_stream_flags &= ~RPB_s_refetch;
                  
                  // Make sure refetched record still fulfills search condition
                  RSB r;                  
                  for (r = rsb; r && r->rsb_type != rsb_boolean ; r = r->rsb_next);
                  if (r && !EVL_boolean(tdbb, (JRD_NOD) r->rsb_arg[0]))
                        return FALSE;
            }

            relation = org_rpb->rpb_relation;


            if (org_rpb->rpb_transaction == transaction->tra_number) {
                  // We already own this record. No writelock required
                  return TRUE;
            }

            stack = NULL;
            switch (prepare_update(tdbb, transaction, org_rpb->rpb_transaction, org_rpb,
                           &temp, 0, &stack, TRUE))
            {
                  case PREPARE_CONFLICT:
                        org_rpb->rpb_stream_flags |= RPB_s_refetch;
                        continue;
                  case PREPARE_LOCKERR:
                        ERR_post(isc_deadlock, isc_arg_gds, isc_update_conflict, 0);
                  case PREPARE_DELETE:
                        return FALSE;
            }

            /* Old record was restored and re-fetched for write.  Now replace it.  */

            org_rpb->rpb_transaction = transaction->tra_number;
            org_rpb->rpb_format_number = org_record->rec_format->fmt_version;
            org_rpb->rpb_b_page = temp.rpb_page;
            org_rpb->rpb_b_line = temp.rpb_line;
            org_rpb->rpb_address = org_record->rec_data;
            org_rpb->rpb_length = org_record->rec_format->fmt_length;
            org_rpb->rpb_flags |= rpb_delta;

            replace_record(tdbb, org_rpb, &stack, transaction);

            if (!(transaction->tra_flags & TRA_system) &&
                  (transaction->tra_save_point))
            {
                  verb_post(tdbb, transaction, org_rpb, 0, 0, FALSE, FALSE);
            }

            /* for an autocommit transaction, mark a commit as necessary */

            if (transaction->tra_flags & TRA_autocommit)
                  transaction->tra_flags |= TRA_perform_autocommit;
            
            return TRUE;
      }
}


BOOLEAN VIO_next_record(TDBB tdbb,
                                    RPB * rpb,
                                    RSB rsb,
                                    JRD_TRA transaction,
                                    BLK pool, BOOLEAN backwards, BOOLEAN onepage)
{
/**************************************
 *
 *    V I O _ n e x t _ r e c o r d
 *
 **************************************
 *
 * Functional description
 *    Get the next record in a record stream.
 *
 **************************************/
      USHORT lock_type;

      SET_TDBB(tdbb);

/* Fetch data page from a modify/erase input stream with a write
   lock. This saves an upward conversion to a write lock when
   refetching the page in the context of the output stream. */

      lock_type = (rpb->rpb_stream_flags & RPB_s_update) ? LCK_write : LCK_read;

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE)
            ib_printf("VIO_next_record (rpb %"SLONGFORMAT", transaction %"
                          SLONGFORMAT", pool %p)\n",
                          rpb->rpb_number, transaction ? transaction->tra_number : 0,
                          pool);
      if (debug_flag > DEBUG_TRACE_INFO)
            ib_printf
                  ("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
#endif

      do
            if (!DPM_next(tdbb, rpb, lock_type, backwards, onepage))
                  return FALSE;
      while (!VIO_chase_record_version(tdbb, rpb, rsb, transaction, pool, FALSE));

#ifdef PC_ENGINE
      if (rsb && rsb->rsb_flags & rsb_stream_type)
            RNG_add_page(rpb->rpb_page);
#endif

      if (pool)
            VIO_data(tdbb, rpb, pool);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_READS_INFO)
            ib_printf
                  ("VIO_next_record got record  %"SLONGFORMAT":%d, rpb_trans %"
                   SLONGFORMAT", flags %d, back %"SLONGFORMAT":%d, fragment %"
                   SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
#endif

      VIO_bump_count(tdbb, DBB_read_seq_count, rpb->rpb_relation, false);

      return TRUE;
}


REC VIO_record(TDBB tdbb, RPB * rpb, FMT format, JrdMemoryPool *pool)
{
/**************************************
 *
 *    V I O _ r e c o r d
 *
 **************************************
 *
 * Functional description
 *    Allocate a record block big enough for a given format.
 *
 **************************************/
      DBB dbb;
      REC record, old;

      SET_TDBB(tdbb);
      dbb = tdbb->tdbb_database;
      CHECK_DBB(dbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE)
            ib_printf("VIO_record (rpb %"SLONGFORMAT", format %d, pool %p)\n",
                          rpb->rpb_number, format ? format->fmt_version : 0,
                          pool);
#endif

/* If format wasn't given, look one up */

      if (!format)
            format = MET_format(tdbb, rpb->rpb_relation, rpb->rpb_format_number);

      if (!(record = rpb->rpb_record)) {
            if (!pool)
                  pool = dbb->dbb_permanent;
            record = rpb->rpb_record = FB_NEW_RPT(*pool, format->fmt_length) rec;
            record->rec_length = format->fmt_length;
      }
      else if (record->rec_length < format->fmt_length) {
            old = record;
            if (record->rec_flags & REC_gc_active)
                  record =
                        replace_gc_record(rpb->rpb_relation, &rpb->rpb_record,
                                                  format->fmt_length);
            else
            {
                  record = FB_NEW_RPT(*MemoryPool::blk_pool(record), format->fmt_length) rec;
                  memcpy(record, rpb->rpb_record, sizeof(rec) + sizeof(SCHAR)*rpb->rpb_record->rec_length);
                  delete rpb->rpb_record;
                  rpb->rpb_record = record;
            }

            record->rec_length = format->fmt_length;
            if (rpb->rpb_prior == old)
                  rpb->rpb_prior = record;
      }

      record->rec_format = format;

      return record;
}


void VIO_start_save_point(TDBB tdbb, JRD_TRA transaction)
{
/**************************************
 *
 *      V I O _ s t a r t _ s a v e _ p o i n t
 *
 **************************************
 *
 * Functional description
 *      Start a new save point for a transaction.
 *
 **************************************/
      SAV sav_point;

      SET_TDBB(tdbb);

      if ( (sav_point = transaction->tra_save_free) ) {
            transaction->tra_save_free = sav_point->sav_next;
            sav_point->sav_flags = 0;
      } else
            sav_point = FB_NEW(*transaction->tra_pool) sav();

      sav_point->sav_number = ++transaction->tra_save_point_number;
      sav_point->sav_next = transaction->tra_save_point;
      transaction->tra_save_point = sav_point;
}


void VIO_store(TDBB tdbb, RPB * rpb, JRD_TRA transaction)
{
/**************************************
 *
 *    V I O _ s t o r e
 *
 **************************************
 *
 * Functional description
 *    Store a new record.
 *
 **************************************/
      JRD_REL relation;
      DSC desc, desc2;
      SSHORT id;
      JRD_REQ request;

      SET_TDBB(tdbb);
      request = tdbb->tdbb_request;

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES)
            ib_printf("VIO_store (rpb %"SLONGFORMAT", transaction %"SLONGFORMAT
                          ")\n", rpb->rpb_number,
                          transaction ? transaction->tra_number : 0);
#endif

      transaction->tra_flags |= TRA_write;
      relation = rpb->rpb_relation;

      if (!(transaction->tra_flags & TRA_system))
            switch ((RIDS) relation->rel_id) {
            case rel_relations:
                  EVL_field(0, rpb->rpb_record, f_rel_name, &desc);
                  DFW_post_work(transaction, dfw_create_relation, &desc, 0);
                  DFW_post_work(transaction, dfw_update_format, &desc, 0);
                  set_system_flag(rpb, f_rel_sys_flag, 0);
                  break;

            case rel_procedures:
                  EVL_field(0, rpb->rpb_record, f_prc_name, &desc);
                  EVL_field(0, rpb->rpb_record, f_prc_id, &desc2);
                  id = MOV_get_long(&desc2, 0);
                  DFW_post_work(transaction, dfw_create_procedure, &desc, id);
                  set_system_flag(rpb, f_prc_sys_flag, 0);
                  break;

            case rel_indices:
                  EVL_field(0, rpb->rpb_record, f_idx_relation, &desc);
                  SCL_check_relation(&desc, SCL_control);
                  EVL_field(0, rpb->rpb_record, f_idx_name, &desc);
                  if (EVL_field(0, rpb->rpb_record, f_idx_exp_blr, &desc2))
                        DFW_post_work(transaction, dfw_create_expression_index, &desc,
                                            tdbb->tdbb_database->dbb_max_idx);
                  else
                        DFW_post_work(transaction, dfw_create_index, &desc, 
                                            tdbb->tdbb_database->dbb_max_idx);
                  break;

            case rel_rfr:
                  EVL_field(0, rpb->rpb_record, f_rfr_rname, &desc);
                  SCL_check_relation(&desc, SCL_control);
                  DFW_post_work(transaction, dfw_update_format, &desc, 0);
                  set_system_flag(rpb, f_rfr_sys_flag, 0);
                  break;

            case rel_classes:
                  EVL_field(0, rpb->rpb_record, f_cls_class, &desc);
                  DFW_post_work(transaction, dfw_compute_security, &desc, 0);
                  break;

            case rel_fields:
                  check_control(tdbb);
                  set_system_flag(rpb, f_fld_sys_flag, 0);
                  break;

            case rel_files:
                  EVL_field(0, rpb->rpb_record, f_file_name, &desc);
                  if (EVL_field(0, rpb->rpb_record, f_file_shad_num, &desc2) &&
                        MOV_get_long(&desc2, 0)) {
                        EVL_field(0, rpb->rpb_record, f_file_flags, &desc2);
                        if (!(MOV_get_long(&desc2, 0) & FILE_inactive))
                              DFW_post_work(transaction, dfw_add_shadow, &desc, 0);
                  }
                  else
                        DFW_post_work(transaction, dfw_add_file, &desc, 0);
                  break;

            case rel_triggers:
                  EVL_field(0, rpb->rpb_record, f_trg_rname, &desc);

                  /* check if this  request go through without checking permissions */
                  if (!(request->req_flags & req_ignore_perm))
                        SCL_check_relation(&desc, SCL_control);

                  EVL_field(0, rpb->rpb_record, f_trg_rname, &desc);
                  DFW_post_work(transaction, dfw_update_format, &desc, 0);
                  EVL_field(0, rpb->rpb_record, f_trg_name, &desc);
                  DFW_post_work(transaction, dfw_create_trigger, &desc, 0);
                  break;

            case rel_priv:
                  EVL_field(0, rpb->rpb_record, f_prv_rname, &desc);
                  EVL_field(0, rpb->rpb_record, f_prv_o_type, &desc2);
                  id = MOV_get_long(&desc2, 0);
                  DFW_post_work(transaction, dfw_grant, &desc, id);
                  break;

            case rel_log:
                  DFW_post_work(transaction, dfw_create_log, 0, 0);
                  break;
                default:    /* Shut up compiler warnings */
                    break;
            }

      rpb->rpb_b_page = 0;
      rpb->rpb_b_line = 0;
      rpb->rpb_flags = 0;
      rpb->rpb_transaction = transaction->tra_number;
      rpb->rpb_window.win_flags = 0;
      LLS_PUSH((BLK) - rpb->rpb_transaction, &rpb->rpb_record->rec_precedence);
      DPM_store(tdbb, rpb, &rpb->rpb_record->rec_precedence, DPM_primary);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES_INFO)
            ib_printf
                  ("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
#endif

      VIO_bump_count(tdbb, DBB_insert_count, relation, false);

      if (!(transaction->tra_flags & TRA_system) &&
            (transaction->tra_save_point) &&
            (transaction->tra_save_point->sav_verb_count))
                  verb_post(tdbb, transaction, rpb, 0, 0, FALSE, FALSE);

/* for an autocommit transaction, mark a commit as necessary */

      if (transaction->tra_flags & TRA_autocommit)
            transaction->tra_flags |= TRA_perform_autocommit;
}


BOOLEAN VIO_sweep(TDBB tdbb, JRD_TRA transaction)
{
/**************************************
 *
 *    V I O _ s w e e p
 *
 **************************************
 *
 * Functional description
 *    Make a garbage collection pass.
 *
 **************************************/
      DBB dbb;
      JRD_REL relation;
      RPB rpb;
      VEC vector;
      USHORT i;

      SET_TDBB(tdbb);
      dbb = tdbb->tdbb_database;

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE)
            ib_printf("VIO_sweep (transaction %"SLONGFORMAT")\n",
                          transaction ? transaction->tra_number : 0);
#endif

      if (transaction->tra_attachment->att_flags & ATT_NO_CLEANUP) {
            return FALSE;
      }

      DPM_scan_pages(tdbb);
      rpb.rpb_record = NULL;
      rpb.rpb_stream_flags = 0;
      rpb.rpb_window.win_flags = WIN_large_scan;

      try {

            for (i = 1; (vector = dbb->dbb_relations) && i < vector->count(); i++)
            {
                  if ((relation = (JRD_REL) (*vector)[i]) && relation->rel_pages &&
                        !(relation->rel_flags & (REL_deleted | REL_deleting)))
                  {
                        rpb.rpb_relation = relation;
                        rpb.rpb_number = -1;
                        rpb.rpb_org_scans = relation->rel_scan_count++;
                        ++relation->rel_sweep_count;
                        while (VIO_next_record(tdbb,
                                                            &rpb,
                                                            NULL,
                                                            transaction,
                                                            0,
                                                            FALSE,
                                                            FALSE))
                        {
                              CCH_RELEASE(tdbb, &rpb.rpb_window);
                              if (relation->rel_flags & REL_deleting)
                                    break;
#ifdef SUPERSERVER
                              if (--tdbb->tdbb_quantum < 0 && !tdbb->tdbb_inhibit) {
                                    (void) JRD_reschedule(tdbb, SWEEP_QUANTUM, TRUE);
                              }
                              transaction->tra_oldest_active = dbb->dbb_oldest_snapshot;
#endif
                        }
                        --relation->rel_sweep_count;
                        --relation->rel_scan_count;
                  }
            }

            delete rpb.rpb_record;

      }     // try
      catch (const std::exception&) {
            delete rpb.rpb_record;
            if (relation)
            {
                  if (relation->rel_sweep_count) {
                        --relation->rel_sweep_count;
                  }
                  if (relation->rel_scan_count) {
                        --relation->rel_scan_count;
                  }
            }
            ERR_punt();
      }
      return TRUE;
}


void VIO_verb_cleanup(TDBB tdbb, JRD_TRA transaction)
{
/**************************************
 *
 *    V I O _ v e r b _ c l e a n u p
 *
 **************************************
 *
 * Functional description
 *    Cleanup after a verb.  If the verb count in the transaction block
 *    is non zero, the verb failed and should be cleaned up.  Cleaning
 *    up ordinarily means just backing out the change, but if we have
 *    an old version we created in this transaction, we replace the current
 *    version with old version.
 *
 *    All changes made by the transaction are kept in one bitmap per
 *    relation.  A second bitmap per relation tracks records for which
 *    we have old data.  The actual data is kept in a linked list stack.
 *    Note that although a record may be changed several times, it will
 *    have only ONE old value -- the value it had before this verb
 *    started.
 *
 **************************************/
      VCT action;
      JRD_REL relation;
      REC record, dead_record;
      RPB rpb, new_rpb;
      SAV sav_point;
      BOOLEAN same_tx = FALSE;
      JrdMemoryPool *old_pool;

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE)
            ib_printf("VIO_verb_cleanup (transaction %"SLONGFORMAT")\n",
                          transaction ? transaction->tra_number : 0);
#endif
      if (transaction->tra_flags & TRA_system)
            return;
            
      sav_point = transaction->tra_save_point;
      if (!sav_point)
            return;

      old_pool = tdbb->tdbb_default;
      tdbb->tdbb_default = transaction->tra_pool;

/* If the current to-be-cleaned-up savepoint is very big, and the next
   level savepoint is the transaction level savepoint, then get rid of
   the transaction level savepoint now (instead of after making the
   transaction level savepoint very very big). */
      transaction->tra_save_point = sav_point->sav_next;
      if (transaction->tra_save_point &&
            (transaction->tra_save_point->sav_flags & SAV_trans_level) &&
            VIO_savepoint_large(sav_point,SAV_LARGE) < 0)
            VIO_verb_cleanup(tdbb, transaction);      /* get rid of tx-level savepoint */

/* Cleanup/merge deferred work/event post */

      if (sav_point->sav_verb_actions
            || (sav_point->sav_flags & SAV_event_post)) {
            if (sav_point->sav_verb_count)
                  DFW_delete_deferred(transaction, sav_point->sav_number);
            else
                  DFW_merge_work(transaction, sav_point->sav_number,
                                       (transaction->
                                          tra_save_point ? transaction->tra_save_point->
                                          sav_number : 0));

            /* The save point may be reused, so reset it.  If the work was
             * not rolled back, set flag for the previous save point.
             */

            if (sav_point->sav_flags & SAV_event_post) {
                  if ((transaction->tra_save_point) && (!sav_point->sav_verb_count))
                        transaction->tra_save_point->sav_flags |= SAV_event_post;

                  sav_point->sav_flags &= ~SAV_event_post;
            }
      }

      while ( (action = sav_point->sav_verb_actions) ) {
            sav_point->sav_verb_actions = action->vct_next;
            relation = action->vct_relation;
            if (sav_point->sav_verb_count || transaction->tra_save_point) {
                  rpb.rpb_relation = relation;
                  rpb.rpb_number = -1;
                  rpb.rpb_record = NULL;
                  rpb.rpb_window.win_flags = 0;
                  rpb.rpb_transaction = transaction->tra_number;

                  if (sav_point->sav_verb_count) {
                        /* This savepoint needs to be undone because the
                           verb_count is not zero. */

                        while (SBM_next
                                 (action->vct_records, &rpb.rpb_number,
                                    RSE_get_forward)) {
                              if (!DPM_get(tdbb, &rpb, LCK_write))
                                    BUGCHECK(186);    /* msg 186 record disappeared */
                              if (rpb.rpb_flags & rpb_delta)
                                    VIO_data(tdbb, &rpb,
                                                 reinterpret_cast <
                                                 blk * >(tdbb->tdbb_default));
                              else
                                    CCH_RELEASE(tdbb, &rpb.rpb_window);
                              if (rpb.rpb_transaction != transaction->tra_number)
                                    BUGCHECK(185);    /* msg 185 wrong record version */
                              if (!action->vct_undo || !action->vct_undo->locate(Firebird::locEqual, rpb.rpb_number))
                                    VIO_backout(tdbb, &rpb, transaction);
                              else {
                                    record = action->vct_undo->current().rec_data;
                                    same_tx = (record->rec_flags & REC_same_tx) ? TRUE : FALSE;

                                    /* Have we done BOTH an update and delete to this record
                                       in the same transaction? */

                                    if (same_tx) {
                                          VIO_backout(tdbb, &rpb, transaction);
                                          /* Nickolay Samofatov, 01 Mar 2003: 
                                            If we don't have data for the record and
                                            it was modified and deleted under our savepoint
                                            we need to back it out to the state as it were
                                            before our transaction started */
                                          if (record->rec_length == 0 && record->rec_flags & REC_new_version) {
                                                if (!DPM_get(tdbb, &rpb, LCK_write))
                                                      BUGCHECK(186);    /* msg 186 record disappeared */
                                                if (rpb.rpb_flags & rpb_delta)
                                                      VIO_data(tdbb, &rpb,
                                                                   reinterpret_cast <
                                                                   blk * >(tdbb->tdbb_default));
                                                else
                                                      CCH_RELEASE(tdbb, &rpb.rpb_window);

                                                VIO_backout(tdbb, &rpb, transaction);
                                          }
                                    }
                                    if (record->rec_length != 0) {
                                          dead_record = rpb.rpb_record;
                                          new_rpb = rpb;
                                          new_rpb.rpb_record = record;
                                          new_rpb.rpb_address = record->rec_data;
                                          new_rpb.rpb_length = record->rec_length;
                                          if (!(rpb.rpb_flags & rpb_delta)) {
                                                if (!DPM_get(tdbb, &rpb, LCK_write))
                                                      BUGCHECK(186);    /* msg 186 record disappeared */
                                                VIO_data(tdbb, &rpb,
                                                             reinterpret_cast <
                                                             blk * >(tdbb->tdbb_default));
                                          }
                                          update_in_place(tdbb, transaction, &rpb, &new_rpb);
                                          if (!(transaction->tra_flags & TRA_system))
                                                garbage_collect_idx(tdbb, &rpb, &new_rpb, NULL);
                                          rpb.rpb_record = dead_record;
                                    }
                              }
                        }
                  }
                  else {
                        /* This savepoint needs to be posted to the previous savepoint. */

                        while (SBM_next
                                 (action->vct_records, &rpb.rpb_number,
                                    RSE_get_forward)) 
                        {
                              if (!action->vct_undo || !action->vct_undo->locate(Firebird::locEqual, rpb.rpb_number))
                                    verb_post(tdbb, transaction, &rpb, 0, 0, FALSE,
                                                  FALSE);
                              else {
                                    BOOLEAN new_ver;
                                    /* Setup more of rpb because verb_post is probably going to
                                       garbage-collect.  Note that the data doesn't need to be set up
                                       because old_data will be used.  (this guarantees that the
                                       rpb points to the first fragment of the record) */

                                    if (!DPM_get(tdbb, &rpb, LCK_read))
                                          BUGCHECK(186);    /* msg 186 record disappeared */
                                    CCH_RELEASE(tdbb, &rpb.rpb_window);
                                    record = action->vct_undo->current().rec_data;
                                    same_tx =
                                          (record->rec_flags & REC_same_tx) ? TRUE : FALSE;
                                    new_ver =
                                          (record->rec_flags & REC_new_version) ? TRUE :
                                          FALSE;
                                    if (record->rec_length != 0) {
                                          new_rpb = rpb;
                                          new_rpb.rpb_record = record;
                                          new_rpb.rpb_address = record->rec_data;
                                          new_rpb.rpb_length = record->rec_length;
                                          verb_post(tdbb, transaction, &rpb, record,
                                                        &new_rpb, same_tx, new_ver);
                                    }
                                    else if (same_tx)
                                          verb_post(tdbb, transaction, &rpb, 0,
                                                        0, TRUE, new_ver);
                              }
                        }
                  }

                  if (rpb.rpb_record)
                        delete rpb.rpb_record;
            }
            SBM_reset(&action->vct_records);
            if (action->vct_undo) {
                  if (action->vct_undo->getFirst()) do {
                        delete action->vct_undo->current().rec_data;
                  } while (action->vct_undo->getNext());
                  delete action->vct_undo;
                  action->vct_undo = NULL;
            }
            action->vct_next = sav_point->sav_verb_free;
            sav_point->sav_verb_free = action;
      }

      sav_point->sav_verb_count = 0;
      sav_point->sav_next = transaction->tra_save_free;
      transaction->tra_save_free = sav_point;

/* If the only remaining savepoint is the 'transaction-level' savepoint
   that was started by TRA_start, then check if it hasn't grown out of
   bounds yet.  If it has, then give up on this transaction-level
   savepoint. */

      if (transaction->tra_save_point &&
            (transaction->tra_save_point->sav_flags & SAV_trans_level) &&
            VIO_savepoint_large(transaction->tra_save_point,SAV_LARGE) < 0)
            VIO_verb_cleanup(tdbb, transaction);      /* get rid of savepoint */

      tdbb->tdbb_default = old_pool;
}



void VIO_merge_proc_sav_points(
                                             TDBB tdbb,
                                             JRD_TRA transaction, SAV * sav_point_list)
{
/**************************************
 *
 *    V I O _ m e r g e _ p r o c _ s a v _ p o i n t s
 *
 **************************************
 *
 * Functional description
 *    Merge all the work done in all the save points in
 *    sav_point_list to the current save point in the
 *    transaction block.
 *
 **************************************/
      SAV sav_point;
      SAV sav_next;
      SLONG sav_number;

      SET_TDBB(tdbb);

      if (transaction->tra_flags & TRA_system)
            return;

      if (!transaction->tra_save_point)
            return;

/* One by one go on putting all savepoints in the sav_point_list on
   top of transaction save points and call VIO_verb_cleanup () */

      for (sav_point = *sav_point_list; sav_point;
             sav_point = sav_point->sav_next) {
            sav_next = sav_point->sav_next;
            sav_number = sav_point->sav_number;

            /* Add it to the front */
            sav_point->sav_next = transaction->tra_save_point;
            transaction->tra_save_point = sav_point;

            VIO_verb_cleanup(tdbb, transaction);
            sav_point = get_free_save_point_block(transaction);
            sav_point->sav_verb_count = 0;
            sav_point->sav_next = sav_next;
            sav_point->sav_number = sav_number;
            *sav_point_list = sav_point;
            sav_point_list = &sav_point->sav_next;
      }

}


static void check_class(
                                    TDBB tdbb,
                                    JRD_TRA transaction,
                                    RPB * old_rpb, RPB * new_rpb, USHORT id)
{
/**************************************
 *
 *    c h e c k _ c l a s s
 *
 **************************************
 *
 * Functional description
 *    A record in a system relation containing a security class is
 *    being change.  Check to see if the security class has changed,
 *    and if so, post the change.
 *
 **************************************/
      DSC desc1, desc2;
      ATT attachment;

      SET_TDBB(tdbb);

      EVL_field(0, old_rpb->rpb_record, id, &desc1);
      EVL_field(0, new_rpb->rpb_record, id, &desc2);
      if (!MOV_compare(&desc1, &desc2))
            return;

      attachment = tdbb->tdbb_attachment;

      SCL_check_access(attachment->att_security_class, 0, 0, 0, SCL_protect,
                               "DATABASE", "");
      DFW_post_work(transaction, dfw_compute_security, &desc2, 0);
}


static void check_control(TDBB tdbb)
{
/**************************************
 *
 *    c h e c k _ c o n t r o l
 *
 **************************************
 *
 * Functional description
 *    Check to see if we have control
 *    privilege on the current database.
 *
 **************************************/
      ATT attachment;

      SET_TDBB(tdbb);

      attachment = tdbb->tdbb_attachment;

      SCL_check_access(attachment->att_security_class,
                               0, 0, 0, SCL_control, "DATABASE", "");
}


static BOOLEAN check_user(TDBB tdbb, DSC * desc)
{
/**************************************
 *
 *    c h e c k _ u s e r
 *
 **************************************
 *
 * Functional description
 *    Validate string against current user name.
 *
 **************************************/
      TEXT *p, *end, *q;

      SET_TDBB(tdbb);

      p = (TEXT *) desc->dsc_address;
      end = p + desc->dsc_length;
      q = tdbb->tdbb_attachment->att_user->usr_user_name;

/* It is OK to not internationalize this function for v4.00 as
 * User names are limited to 7-bit ASCII for v4.00
 */

      for (; p < end && *p != ' '; p++, q++)
            if (UPPER7(*p) != UPPER7(*q))
                  return FALSE;

      return (*q) ? FALSE : TRUE;
}


static void delete_(TDBB tdbb, RPB * rpb, SLONG prior_page, JrdMemoryPool *pool)
{
/**************************************
 *
 *    d e l e t e
 *
 **************************************
 *
 * Functional description
 *    Delete a record an all of its fragments.  This assumes the
 *    record has already been fetched for write.  If a pool is given,
 *    the caller has requested that data be fetched as the record is
 *    deleted.
 *
 **************************************/
      REC record, prior;
      RPB temp_rpb;
      UCHAR *tail, *tail_end, differences[MAX_DIFFERENCES];

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES)
            ib_printf("delete_ (rpb %"SLONGFORMAT", prior_page %ld, pool %p)\n",
                          rpb->rpb_number, prior_page,
                          pool);
      if (debug_flag > DEBUG_WRITES_INFO)
            ib_printf
                  ("   delete_ record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
#endif
      if (!pool || (rpb->rpb_flags & rpb_deleted)) {
            prior = NULL;
            tail = tail_end = NULL;
      }
      else {
            record = VIO_record(tdbb, rpb, 0, pool);
            if ( (prior = rpb->rpb_prior) ) {
                  tail = differences;
                  tail_end = differences + sizeof(differences);
                  if (prior != record)
                        MOVE_FASTER(prior->rec_data, record->rec_data,
                                          record->rec_format->fmt_length);
            }
            else {
                  tail = record->rec_data;
                  tail_end = tail + record->rec_length;
            }
            tail =
                  reinterpret_cast <
                  UCHAR *
                  >(SQZ_decompress
                    (reinterpret_cast < char *>(rpb->rpb_address), rpb->rpb_length,
                     reinterpret_cast < char *>(tail),
                     reinterpret_cast < char *>(tail_end)));
            rpb->rpb_prior = (rpb->rpb_flags & rpb_delta) ? record : 0;
      }

      temp_rpb = *rpb;
      DPM_delete(tdbb, &temp_rpb, prior_page);
      tail = delete_tail(tdbb, &temp_rpb, temp_rpb.rpb_page, tail, tail_end);

      if (pool && prior)
            SQZ_apply_differences(record, reinterpret_cast < char *>(differences),
                                            reinterpret_cast < char *>(tail));
}


static UCHAR *delete_tail(
                                      TDBB tdbb,
                                      RPB * rpb,
                                      SLONG prior_page, UCHAR * tail, UCHAR * tail_end)
{
/**************************************
 *
 *    d e l e t e _ t a i l
 *
 **************************************
 *
 * Functional description
 *    Delete the tail of a record.  If no tail, don't do nuttin'.
 *    If the address of a record tail has been passed, fetch data.
 *
 **************************************/

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES)
            ib_printf
                  ("delete_tail (rpb %"SLONGFORMAT", prior_page %ld, tail %p, tail_end %p)\n",
                   rpb->rpb_number, prior_page, tail, tail_end);
      if (debug_flag > DEBUG_WRITES_INFO)
            ib_printf
                  ("   tail of record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
#endif

      while (rpb->rpb_flags & rpb_incomplete) {
            rpb->rpb_page = rpb->rpb_f_page;
            rpb->rpb_line = rpb->rpb_f_line;

            /* Since the callers are modifying this record, it should not be
               garbage collected. */

            if (!DPM_fetch(tdbb, rpb, LCK_write))
                  BUGCHECK(248);          /* msg 248 cannot find record fragment */
            if (tail)
                  tail =
                        reinterpret_cast <
                        UCHAR *
                        >(SQZ_decompress
                          (reinterpret_cast < char *>(rpb->rpb_address),
                           rpb->rpb_length, reinterpret_cast < char *>(tail),
                           reinterpret_cast < char *>(tail_end)));
            DPM_delete(tdbb, rpb, prior_page);
            prior_page = rpb->rpb_page;
      }

      return tail;
}


static void expunge(TDBB tdbb, RPB * rpb, JRD_TRA transaction, SLONG prior_page)
{
/**************************************
 *
 *    e x p u n g e
 *
 **************************************
 *
 * Functional description
 *    Expunge a fully mature deleted record.  Get rid of the record
 *    and all of the ancestors.  Be particulary careful since this
 *    can do a lot of damage.
 *
 **************************************/
      RPB temp;

      SET_TDBB(tdbb);


#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES)
            ib_printf("expunge (rpb %"SLONGFORMAT", transaction %"SLONGFORMAT
                          ", prior_page %"SLONGFORMAT")\n",
                          rpb->rpb_number, transaction ? transaction->tra_number : 0,
                          prior_page);
#endif

      if (transaction->tra_attachment->att_flags & ATT_no_cleanup)
            return;

/* Re-fetch the record */

      if (!DPM_get(tdbb, rpb, LCK_write))
            return;
#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES_INFO)
            ib_printf
                  ("   expunge record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
#endif

/* Make sure it looks kosher and delete the record. */

      if (!(rpb->rpb_flags & rpb_deleted) ||
            rpb->rpb_transaction >= transaction->tra_oldest_active) {
            CCH_RELEASE(tdbb, &rpb->rpb_window);
            return;
      }

      delete_(tdbb, rpb, prior_page, 0);

/* If there aren't any old versions, don't worry about garbage collection. */

      if (!rpb->rpb_b_page)
            return;

/* Delete old versions fetching data for garbage collection. */

      temp = *rpb;
      garbage_collect(tdbb, &temp, rpb->rpb_page, 0);
      VIO_bump_count(tdbb, DBB_expunge_count, rpb->rpb_relation, false);
}


static void garbage_collect(
                                          TDBB tdbb,
                                          RPB * rpb, SLONG prior_page, LLS staying)
{
/**************************************
 *
 *    g a r b a g e _ c o l l e c t
 *
 **************************************
 *
 * Functional description
 *    Garbage collect a chain of back record.  This is called from
 *    "purge" and "expunge."  One enters this routine with an
 *    inactive RPB, describing a records which has either
 *    1) just been deleted or
 *    2) just had its back pointers set to zero
 *    Therefor we can do a fetch on the back pointers we've got
 *    because we have the last existing copy of them.
 *
 **************************************/

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES)
            ib_printf("garbage_collect (rpb %"SLONGFORMAT", prior_page %"SLONGFORMAT
                          ", staying)\n",
                          rpb->rpb_number, prior_page);
      if (debug_flag > DEBUG_WRITES_INFO)
            ib_printf
                  ("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
#endif

/* Delete old versions fetching data for garbage collection. */

      LLS going = NULL;

      while (rpb->rpb_b_page != 0) {
            rpb->rpb_record = NULL;
            prior_page = rpb->rpb_page;
            rpb->rpb_page = rpb->rpb_b_page;
            rpb->rpb_line = rpb->rpb_b_line;
            if (!DPM_fetch(tdbb, rpb, LCK_write))
                  BUGCHECK(291);          /* msg 291 cannot find record back version */
            delete_(tdbb, rpb, prior_page, tdbb->tdbb_default);
            if (rpb->rpb_record) {
                  LLS_PUSH(rpb->rpb_record, &going);
            }
#ifdef SUPERSERVER
            /* Don't monopolize the server while chasing long
               back version chains. */

            if (--tdbb->tdbb_quantum < 0 && !tdbb->tdbb_inhibit)
                  (void) JRD_reschedule(tdbb, 0, TRUE);
#endif
      }

      BLB_garbage_collect(tdbb, going, staying, prior_page, rpb->rpb_relation);
      IDX_garbage_collect(tdbb, rpb, going, staying);

      while (going)
            delete LLS_POP(&going);
}


static void garbage_collect_idx(
                                                TDBB tdbb,
                                                RPB * org_rpb, RPB * new_rpb, REC old_data)
{
/**************************************
 *
 *    g a r b a g e _ c o l l e c t _ i d x
 *
 **************************************
 *
 * Functional description
 *    Garbage collect indices for which it is
 *    OK for other transactions to create indices with the same
 *    values.
 *
 **************************************/
      LLS going, staying;

      SET_TDBB(tdbb);

/* There should be a way to quickly check if there are indices and/or if there
   are blob-colums. */

/* Garbage collect.  Start by getting all existing old versions (other
   than the immediate two in question). */

      going = staying = NULL;
      list_staying(tdbb, org_rpb, &staying);

/* The data that is going is passed either via old_data, or via org_rpb. */

      if (old_data)
            LLS_PUSH(old_data, &going);
      else
            LLS_PUSH(org_rpb->rpb_record, &going);

      BLB_garbage_collect(tdbb, going, staying, org_rpb->rpb_page,
                                    org_rpb->rpb_relation);
      IDX_garbage_collect(tdbb, org_rpb, going, staying);

      LLS_POP(&going);

      while (staying)
            delete LLS_POP(&staying);
}


#ifdef GARBAGE_THREAD
static void THREAD_ROUTINE garbage_collector(DBB dbb)
{
/**************************************
 *
 *    g a r b a g e _ c o l l e c t o r
 *
 **************************************
 *
 * Functional description
 *    Garbage collect the data pages marked in a
 *    relation's garbage collection bitmap. The
 *    hope is that offloading the computation
 *    and I/O burden of garbage collection will
 *    improve query response time and throughput.
 *
 **************************************/
      struct tdbb thd_context, *tdbb;
      ISC_STATUS_ARRAY status_vector;
      SLONG count, dp_sequence, last;
      ULONG id;
      JRD_REL relation;
      JRD_TRA transaction;
      RPB rpb;
      EVENT gc_event;
      bool found = false, flush = false;

      THREAD_ENTER;
      CHECK_DBB(dbb);
      gc_event = dbb->dbb_gc_event;
      MOVE_CLEAR(&rpb, sizeof(struct rpb));
      MOVE_CLEAR(status_vector, sizeof(status_vector));
      relation = 0;
      transaction = 0;

/* Establish a thread context. */
/* Note: Since this function operates as its own thread,
   we have no need to restore the THREAD CONTEXT on exit.
   Once we reach the end, the thread will die, thus implicitly
   killing all its contexts. */
      SET_THREAD_DATA;
      tdbb->tdbb_database = dbb;
      tdbb->tdbb_default = dbb->dbb_permanent;
      tdbb->tdbb_status_vector = status_vector;
      tdbb->tdbb_quantum = SWEEP_QUANTUM;
      tdbb->tdbb_flags = TDBB_sweeper;

/* Surrender if resources to start up aren't available. */

      try {
            ISC_event_init(gc_event, 0, 0);

/* Pseudo attachment needed for lock owner identification. */

            tdbb->tdbb_attachment = FB_NEW(*dbb->dbb_permanent) att();
            tdbb->tdbb_attachment->att_database = dbb;
            tdbb->tdbb_attachment->att_filename = dbb->dbb_filename;
            tdbb->tdbb_attachment->att_flags = ATT_garbage_collector;

            rpb.rpb_window.win_flags = WIN_garbage_collector;

            LCK_init(tdbb, LCK_OWNER_attachment);

/* Notify our creator that we have started */
            dbb->dbb_flags |= DBB_garbage_collector;
            ISC_event_post(dbb->dbb_gc_event_init);

      }     // try
      catch (const std::exception&) {
            goto gc_exit;
      }

      try {

/* Initialize status vector after logging error. */

            MOVE_CLEAR(status_vector, sizeof(status_vector));

/* The garbage collector flag is cleared to request the thread
   to finish up and exit. */

            while (dbb->dbb_flags & DBB_garbage_collector) {

                  count = ISC_event_clear(gc_event);
                  dbb->dbb_flags |= DBB_gc_active;
                  found = false;
                  relation = 0;

                  /* If background thread activity has been suspended because
                     of I/O errors then idle until the condition is cleared.
                     In particular, make worker threads perform their own
                     garbage collection so that errors are reported to users. */

                  if (dbb->dbb_flags & DBB_suspend_bgio) {
                        ATT attachment;

                        for (attachment = dbb->dbb_attachments;
                               attachment != 0; attachment = attachment->att_next) {
                              if (attachment->att_flags & ATT_notify_gc) {
                                    attachment->att_flags &= ~ATT_notify_gc;
                                    attachment->att_flags |= ATT_disable_notify_gc;
                              }
                        }

                        while (dbb->dbb_flags & DBB_suspend_bgio) {
                              count = ISC_event_clear(gc_event);
                              THREAD_EXIT;
                              ISC_event_wait(1, &gc_event, &count, 10 * 1000000, (FPTR_VOID) 0, 0);
                              THREAD_ENTER;
                              if (!(dbb->dbb_flags & DBB_garbage_collector)) {
                                    goto gc_exit;
                              }
                        }

                        for (attachment = dbb->dbb_attachments;
                               attachment != 0; attachment = attachment->att_next) {
                              if (attachment->att_flags & ATT_disable_notify_gc) {
                                    attachment->att_flags &= ~ATT_disable_notify_gc;
                                    attachment->att_flags |= ATT_notify_gc;
                              }
                        }
                  }

                  /* Scan relation garbage collection bitmaps for candidate data pages.
                     Express interest in the relation to prevent it from being deleted
                     out from under us while garbage collection is in-progress. */

                  VEC vector = dbb->dbb_relations;
                  for (id = 0; vector && id < vector->count(); ++id) {

                        relation = (JRD_REL) (*vector)[id];

                        if (relation && relation->rel_gc_bitmap != 0 &&
                                    !(relation->rel_flags & (REL_deleted | REL_deleting))) {

                              ++relation->rel_sweep_count;
                              dp_sequence = -1;
                              rpb.rpb_relation = relation;

                              while (SBM_next(relation->rel_gc_bitmap, &dp_sequence, RSE_get_forward)) {
                                    
                                    if (!(dbb->dbb_flags & DBB_garbage_collector)) {
                                          --relation->rel_sweep_count;
                                          goto gc_exit;
                                    }

                                    SBM_clear(relation->rel_gc_bitmap, dp_sequence);

                                    if (!transaction) {
                                          /* Start a "precommitted" transaction by using read-only,
                                             read committed. Of particular note is the absence of a
                                             transaction lock which means the transaction does not
                                             inhibit garbage collection by its very existence. */

                                          transaction = TRA_start(tdbb, sizeof(gc_tpb), const_cast<char*>(gc_tpb));
                                          tdbb->tdbb_transaction = transaction;
                                    }
                                    else {
                                          /* Refresh our notion of the oldest transactions for
                                             efficient garbage collection. This is very cheap. */

                                          transaction->tra_oldest = dbb->dbb_oldest_transaction;
                                          transaction->tra_oldest_active = dbb->dbb_oldest_snapshot;
                                    }

                                    found = flush = true;
                                    rpb.rpb_number = (dp_sequence * dbb->dbb_max_records) - 1;
                                    last = rpb.rpb_number + dbb->dbb_max_records;

                                    /* Attempt to garbage collect all records on the data page. */

                                    while (VIO_next_record(tdbb, &rpb, NULL, transaction, NULL, FALSE, TRUE)) {

                                          CCH_RELEASE(tdbb, &rpb.rpb_window);

                                          if (!(dbb->dbb_flags & DBB_garbage_collector)) {
                                                --relation->rel_sweep_count;
                                                goto gc_exit;
                                          }
                                          if (relation->rel_flags & REL_deleting) {
                                                goto rel_exit;
                                          }
                                          if (--tdbb->tdbb_quantum < 0 && !tdbb->tdbb_inhibit) {
                                                (void) JRD_reschedule(tdbb, SWEEP_QUANTUM, TRUE);
                                          }
                                          if (rpb.rpb_number >= last) {
                                                break;
                                          }
                                    }
                              }

rel_exit:
                              dp_sequence = -1;

                              if (!SBM_next(relation->rel_gc_bitmap, &dp_sequence, RSE_get_forward)) {
                                    /* If the bitmap is empty then release it */
                                    SBM_release(relation->rel_gc_bitmap);
                                    relation->rel_gc_bitmap = 0;
                              }
                              else {
                                    /* Otherwise release bitmap segments that have been cleared. */
                                    while (SBM_next(relation->rel_gc_bitmap, &dp_sequence, RSE_get_forward)) {
                                          ;     // do nothing
                                    }
                              }
                              --relation->rel_sweep_count;
                        }
                  }

                  /* If there's more work to do voluntarily ask to be rescheduled.
                     Otherwise, wait for event notification. */

                  if (found) {
                        (void) JRD_reschedule(tdbb, SWEEP_QUANTUM, TRUE);
                  }
                  else {
                        dbb->dbb_flags &= ~DBB_gc_pending;

                        /* Make no mistake about it, garbage collection is our first
                           priority. But if there's no garbage left to collect, assist
                           the overworked cache writer and reader threads. */

                        while (dbb->dbb_flags & DBB_garbage_collector &&
                                 !(dbb->dbb_flags & DBB_gc_pending)) {

                              if (CCH_free_page(tdbb) || CCH_prefetch_pages(tdbb)) {
                                    continue;
                              }
                              if (flush) {
                                    /* As a last resort, flush garbage collected pages to
                                       disk. This isn't strictly necessary but contributes
                                       to the supply of free pages available for user
                                       transactions. It also reduces the likelihood of
                                       orphaning free space on lower precedence pages that
                                       haven't been written if a crash occurs. */

                                    flush = false;
                                    if (transaction) {
                                          CCH_flush(tdbb, (USHORT) FLUSH_SWEEP, 0);
                                    }
                                    continue;
                              }
                              dbb->dbb_flags &= ~DBB_gc_active;
                              THREAD_EXIT;
                              int timeout = ISC_event_wait(1, &gc_event, &count, 10 * 1000000, (FPTR_VOID) 0, 0);
                              THREAD_ENTER;
                              dbb->dbb_flags |= DBB_gc_active;
                              if (!timeout) {
                                    count = ISC_event_clear(gc_event);
                              }
                        }
                  }
            }
    }
      catch (const std::exception&) {
            /* Perfunctory error reporting -- got any better ideas ? */

            gds__log_status(dbb->dbb_file->fil_string, status_vector);
            if (relation && relation->rel_sweep_count) {
                  --relation->rel_sweep_count;
            }
    }


gc_exit:

    try {

            if (rpb.rpb_record) {
                  delete rpb.rpb_record;  /* Possibly allocated from permanent pool. */
            }
            if (transaction) {
                  TRA_commit(tdbb, transaction, FALSE);
            }
            if (tdbb->tdbb_attachment) {
                  LCK_fini(tdbb, LCK_OWNER_attachment);
                  delete tdbb->tdbb_attachment;
            }
            dbb->dbb_flags &= ~(DBB_garbage_collector | DBB_gc_active | DBB_gc_pending);
            /* Notify the finalization caller that we're finishing. */
            ISC_event_post(dbb->dbb_gc_event_fini);   
            ISC_event_fini(gc_event);

            RESTORE_THREAD_DATA;
            THREAD_EXIT;

      }     // try
      catch (const std::exception&) {
            /* Perfunctory error reporting -- got any better ideas ? */

            gds__log_status(dbb->dbb_file->fil_string, status_vector);
      }
}
#endif


static SAV get_free_save_point_block(JRD_TRA transaction)
{
/**************************************
 *
 *      g e t _ f r e e _ s a v e _ p o i n t _ b l o c k
 *
 **************************************
 *
 * Functional description
 *      Get a free save point block from free list.
 *    If not available make one.
 *
 **************************************/
      SAV sav_point;

      if ( (sav_point = transaction->tra_save_free) )
            transaction->tra_save_free = sav_point->sav_next;
      else
            sav_point = FB_NEW(*transaction->tra_pool) sav();

      return sav_point;
}


static void list_staying(TDBB tdbb, RPB * rpb, LLS * staying)
{
/**************************************
 *
 *    l i s t _ s t a y i n g
 *
 **************************************
 *
 * Functional description
 *    Get all the data that's staying so we can clean up indexes etc.
 *    without losing anything.  Note that in the middle somebody could
 *    modify the record -- worse yet, somebody could modify it, commit,
 *    and have somebody else modify it, so if the back pointers on the
 *    original record change throw out what we've got and start over.
 *    "All the data that's staying" is: all the versions of the input
 *    record (rpb) that are stored in the relation.
 *
 **************************************/
      ULONG next_page;
      REC data;
      USHORT next_line, depth, max_depth;
      RPB temp;

      SET_TDBB(tdbb);

      data = rpb->rpb_prior;
      next_page = rpb->rpb_page;
      next_line = rpb->rpb_line;
      max_depth = 0;

      for (;;) {
            /* Each time thru the loop, start from the latest version of the record
               because during the call to VIO_data (below), things might change. */

            temp = *rpb;
            depth = 0;

            /* If the entire record disappeared, then there is nothing staying. */
            if (!DPM_fetch(tdbb, &temp, LCK_read)) {
                  while (*staying)
                        delete LLS_POP(staying);
                  return;
            }

            /* If anything changed, then start all over again.  This time with the
               new, latest version of the record. */

            if (temp.rpb_b_page != rpb->rpb_b_page ||
                  temp.rpb_b_line != rpb->rpb_b_line ||
                  temp.rpb_flags != rpb->rpb_flags)
            {
                  while (*staying) {
                        delete LLS_POP(staying);
                  }
                  next_page = temp.rpb_page;
                  next_line = temp.rpb_line;
                  max_depth = 0;
                  *rpb = temp;
            }

            depth++;

            /* Each time thru the for-loop, we process the next older version.
               The while-loop finds this next older version. */

            while (temp.rpb_b_page &&
                     !(temp.rpb_page == (SLONG) next_page && temp.rpb_line == (SSHORT) next_line))
            {
                  temp.rpb_prior = (temp.rpb_flags & rpb_delta) ? data : NULL;
                  DPM_fetch_back(tdbb, &temp, LCK_read, 1);
                  depth++;
#ifdef SUPERSERVER
                  /* Don't monopolize the server while chasing long
                     back version chains. */

                  if (--tdbb->tdbb_quantum < 0 && !tdbb->tdbb_inhibit) {
                        (void) JRD_reschedule(tdbb, 0, TRUE);
                  }
#endif
            }

            /* If there is a next older version, then process it: remember that
               version's data in 'staying'. */

            if (temp.rpb_page == (SLONG) next_page && temp.rpb_line == (SSHORT) next_line)
            {
                  next_page = temp.rpb_b_page;
                  next_line = temp.rpb_b_line;
                  temp.rpb_record = NULL;
                  if (temp.rpb_flags & rpb_deleted) {
                        CCH_RELEASE(tdbb, &temp.rpb_window);
                  } else {
                        VIO_data(tdbb, &temp,
                                     reinterpret_cast < blk * >(tdbb->tdbb_default));
                        LLS_PUSH(temp.rpb_record, staying);
                        data = temp.rpb_record;
                  }
                  max_depth = depth;
                  if (!next_page)
                        break;
            }
            else {
                  CCH_RELEASE(tdbb, &temp.rpb_window);
                  break;
            }
      }

/* If the current number of back versions (depth) is smaller than the number
   of back versions that we saw in a previous iteration (max_depth), then
   somebody else must have been garbage collecting also.  Remove the entries
   in 'staying' that have already been garbage collected. */
      while (depth < max_depth--) {
            if (*staying) {
                  delete LLS_POP(staying);
            }
      }
}


#ifdef GARBAGE_THREAD
static void notify_garbage_collector(TDBB tdbb, RPB * rpb)
{
/**************************************
 *
 *    n o t i f y _ g a r b a g e _ c o l l e c t o r
 *
 **************************************
 *
 * Functional description
 *    Notify the garbage collector that there is work to be
 *    done. Each relation has a garbage collection sparse
 *    bitmap where each bit corresponds to a data page
 *    sequence number of a data page known to have records
 *    which are candidates for garbage collection.
 *
 **************************************/

      DBB dbb      = tdbb->tdbb_database;
      JRD_REL relation = rpb->rpb_relation;

/* If this is a large sequential scan then defer the release
   of the data page to the LRU tail until the garbage collector
   can garbage collect the page. */

      if (rpb->rpb_window.win_flags & WIN_large_scan)
            rpb->rpb_window.win_flags |= WIN_garbage_collect;

/* A relation's garbage collect bitmap is allocated
   from the database permanent pool. */

      JrdMemoryPool* old_pool = tdbb->tdbb_default;

      tdbb->tdbb_default = dbb->dbb_permanent;
      SLONG dp_sequence = rpb->rpb_number / dbb->dbb_max_records;
      SBM_set(tdbb, &relation->rel_gc_bitmap, dp_sequence);
      tdbb->tdbb_default = old_pool;

/* If the garbage collector isn't active then poke
   the event on which it sleeps to awaken it. */

      dbb->dbb_flags |= DBB_gc_pending;
      if (!(dbb->dbb_flags & DBB_gc_active)) {
            ISC_event_post(dbb->dbb_gc_event);
      }
}
#endif


static int prepare_update(    TDBB  tdbb,
                                          JRD_TRA           transaction,
                                          SLONG commit_tid_read,
                                          RPB*  rpb,
                                          RPB*  temp,
                                          RPB*  new_rpb,
                                          LLS*  stack,
                                          BOOLEAN writelock)
{
/**************************************
 *
 *    p r e p a r e _ u p d a t e
 *
 **************************************
 *
 * Functional description
 *    Prepare for a modify or erase.  Store the old version
 *    of a record, fetch the current version, check transaction
 *    states, etc.
 *
 **************************************/
      USHORT state;
      REC record;
      RPB temp2, org_rpb;
      UCHAR differences[MAX_DIFFERENCES];
      USHORT l;
      SLONG update_conflict_trans = -1;

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE_ALL) {
            ib_printf
                  ("prepare_update (transaction %"SLONGFORMAT
                   ", commit_tid read %ld, rpb %"SLONGFORMAT", ",
                   transaction ? transaction->tra_number : 0, commit_tid_read,
                   rpb ? rpb->rpb_number : 0);
            ib_printf(" temp_rpb %"SLONGFORMAT", new_rpb %"SLONGFORMAT", stack)\n",
                          temp ? temp->rpb_number : 0,
                          new_rpb ? new_rpb->rpb_number : 0);
      }
      if (debug_flag > DEBUG_TRACE_ALL_INFO)
            ib_printf
                  ("   old record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT
                   ":%d, prior %p\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line, rpb->rpb_prior);
#endif

/* We're almost ready to go.  To erase the record, we must first
   make a copy of the old record someplace else.  Then we must re-fetch
   the record (for write) and verify that it is legal for us to
   erase it -- that it was written by a transaction that was committed
   when we started.  If not, the transaction that wrote the record
   is either active, dead, or in limbo.  If the transaction is active,
   wait for it to finish.  If it commits, we can't procede and must
   return an update conflict.  If the transaction is dead, back out the
   old version of the record and try again.  If in limbo, punt.

   The above is true only for concurrency & consistency mode transactions.
   For read committed transactions, check if the latest commited version
   is the same as the version that was read for the update.  If yes,
   the update can take place.  If some other transaction has modified
   the record and committed, then an update error will be returned.*/

      *temp = *rpb;
      record = rpb->rpb_record;

/* Mark the record as chained version, and re-store it */

      temp->rpb_address = record->rec_data;
      temp->rpb_length = record->rec_format->fmt_length;
      temp->rpb_format_number = record->rec_format->fmt_version;
      temp->rpb_flags = rpb_chained;

      if (temp->rpb_prior)
            temp->rpb_flags |= rpb_delta;

/* If it makes sense, store a differences record */

      if (new_rpb)
      {
            l = SQZ_differences(reinterpret_cast<char*>(new_rpb->rpb_address),
                                          new_rpb->rpb_length,
                                          reinterpret_cast<char*>(temp->rpb_address),
                                          temp->rpb_length,
                                          reinterpret_cast<char*>(differences),
                                          sizeof(differences));
            if ((l < sizeof(differences)) && (l < temp->rpb_length))
            {
                  temp->rpb_address = differences;
                  temp->rpb_length = l;
                  new_rpb->rpb_flags |= rpb_delta;
            }
      }
      
      if (writelock) {
        temp->rpb_address = differences;
        temp->rpb_length = SQZ_no_differences((SCHAR*) differences, temp->rpb_length);
      }

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_WRITES_INFO)
      {
            if (new_rpb)
            {
                  ib_printf("    new record is%sa delta \n",
                                (new_rpb->rpb_flags & rpb_delta) ? " " : " NOT ");
            }
      }
#endif

      temp->rpb_number = rpb->rpb_number;
      DPM_store(tdbb, temp, stack, DPM_secondary);

/* Re-fetch the original record for write in anticipation of
   replacing it with a completely new version.  Make sure it
   was the same one we stored above. */

      while (TRUE)
      {
            org_rpb.rpb_flags = rpb->rpb_flags;
            org_rpb.rpb_f_line = rpb->rpb_f_line;
            org_rpb.rpb_f_page = rpb->rpb_f_page;

            if (!DPM_get(tdbb, rpb, LCK_write))
            {
                  /* There is no reason why this record would disappear for a
                     snapshot transaction. */
                  if (!(transaction->tra_flags & TRA_read_committed))
                  {
                        BUGCHECK(186);    /* msg 186 record disappeared */
                  }
                  else
                  {
                        /* A read-committed transaction, on the other hand, doesn't
                           insist on the presence of any version, so versions of records
                           and entire records it has already read might be garbage-collected. */
                        if (!DPM_fetch(tdbb, temp, LCK_write)) {
                              BUGCHECK(291);    /* msg 291 cannot find record back version */
                        }
                        delete_(tdbb, temp, (SLONG) 0, 0);
                        return PREPARE_DELETE;
                  }
            }


            state = TRA_snapshot_state(tdbb, transaction, rpb->rpb_transaction);

            /* Reset the garbage collect active flag if the transaction state is
               in a terminal state. If committed it must have been a precommitted
               transaction that was backing out a dead record version and the
               system crashed. Clear the flag and set the state to tra_dead to
               reattempt the backout. */

            if (rpb->rpb_flags & rpb_gc_active)
            {
                  switch (state) {
                  case tra_committed:
                        state = tra_dead;
                        rpb->rpb_flags &= ~rpb_gc_active;
                        break;

                  case tra_dead:
                        rpb->rpb_flags &= ~rpb_gc_active;
                        break;

                  default:
                        break;
                  }
            }

            switch (state) {
            case tra_committed:
#ifdef VIO_DEBUG
                  if (debug_flag > DEBUG_READS_INFO)
                        ib_printf
                              ("    record's transaction (%"SLONGFORMAT
                               ") is committed (my TID - %"SLONGFORMAT")\n",
                               rpb->rpb_transaction, transaction->tra_number);
#endif
                  if (rpb->rpb_flags & rpb_deleted) {
                        CCH_RELEASE(tdbb, &rpb->rpb_window);
                        /* get rid of the back records we just created */
                        if (!
                              (transaction->
                               tra_attachment->att_flags & ATT_no_cleanup)) {
                              if (!DPM_fetch(tdbb, temp, LCK_write))
                                    BUGCHECK(291);    /* msg 291 cannot find record back version */
                              delete_(tdbb, temp, (SLONG) 0, 0);
                        }
                        if (writelock) return PREPARE_DELETE;
                        IBERROR(188);     /* msg 188 cannot update erased record */
                  }

                  /* For read committed transactions, if the record version we read
                   * and started the update
                   * has been updated by another transaction which committed in the
                   * meantime, we cannot proceed further - update conflict error.
                   */

                  if ((transaction->tra_flags & TRA_read_committed) &&
                        (commit_tid_read != rpb->rpb_transaction)) {
                        CCH_RELEASE(tdbb, &rpb->rpb_window);
                        if (!DPM_fetch(tdbb, temp, LCK_write))
                              BUGCHECK(291);    /* msg 291 cannot find record back version */
                        delete_(tdbb, temp, (SLONG) 0, 0);
                        return PREPARE_CONFLICT;
                  }

                  /*
                   * The case statement for tra_us has been pushed down to this
                   * current position as we donot want to give update conflict
                   * errors and the "cannot update erased record" within the same
                   * transaction. We were getting these erroe in case of triggers.
                   * A pre-delete trigger could update or delete a record which we
                   * are then tring to change.
                   * In order to remove these changes and restore original behaviour,
                   * move this case statement above the 2 "if" statements.
                   * smistry 23-Aug-99
                   */
            case tra_us:
#ifdef VIO_DEBUG
                  if (debug_flag > DEBUG_READS_INFO && state == tra_us)
                        ib_printf
                              ("    record's transaction (%"SLONGFORMAT
                               ") is us (my TID - %"SLONGFORMAT")\n",
                               rpb->rpb_transaction, transaction->tra_number);

#endif
                  if (rpb->rpb_b_page != temp->rpb_b_page ||
                        rpb->rpb_b_line != temp->rpb_b_line ||
                        rpb->rpb_transaction != temp->rpb_transaction ||
                        (rpb->rpb_flags & rpb_delta) != (temp->rpb_flags & rpb_delta)
                        || rpb->rpb_flags != org_rpb.rpb_flags
                        || (rpb->rpb_flags & rpb_incomplete)
                        && (rpb->rpb_f_page != org_rpb.rpb_f_page
                              || rpb->rpb_f_line != org_rpb.rpb_f_line)) {

                        /* the primary copy of the record was dead and someone else
                           backed it out for us.  Our data is OK but our pointers
                           aren't, so get rid of the record we created and try again
                         */

                        CCH_RELEASE(tdbb, &rpb->rpb_window);
                        if (!
                              (transaction->
                               tra_attachment->att_flags & ATT_no_cleanup)) {
                              temp2 = *temp;
                              if (!DPM_fetch(tdbb, &temp2, LCK_write))
                                    BUGCHECK(291);    /* msg 291 cannot find record back version */
                              delete_(tdbb, &temp2, (SLONG) 0, 0);
                        }
                        temp->rpb_b_page = rpb->rpb_b_page;
                        temp->rpb_b_line = rpb->rpb_b_line;
                        temp->rpb_flags &= ~rpb_delta;
                        temp->rpb_flags |= rpb->rpb_flags & rpb_delta;
                        temp->rpb_transaction = rpb->rpb_transaction;
                        DPM_store(tdbb, temp, stack, DPM_secondary);
                        continue;
                  }
                  LLS_PUSH((BLK) temp->rpb_page, stack);
                  return PREPARE_OK;

            case tra_active:
            case tra_limbo:
#ifdef VIO_DEBUG
                  if (debug_flag > DEBUG_READS_INFO) {
                        ib_printf
                              ("    record's transaction (%"SLONGFORMAT
                               ") is %s (my TID - %"SLONGFORMAT")\n",
                               rpb->rpb_transaction,
                               (state == tra_active) ? "active" : "limbo",
                               transaction->tra_number);
                  }

#endif
                  CCH_RELEASE(tdbb, &rpb->rpb_window);

                  /* Wait as long as it takes for an active transaction which has modified
                     the record. If an active transaction has used its TID to safely
                     backout a fragmented dead record version, spin wait because it will
                     finish shortly. */

                  if (!(rpb->rpb_flags & rpb_gc_active))
                        state =
                              TRA_wait(tdbb, transaction, rpb->rpb_transaction, TRUE);
                  else {
                        BOOLEAN wait_flag;

                        wait_flag =
                              (transaction->tra_flags & TRA_nowait) ? FALSE : TRUE;
                        transaction->tra_flags |= TRA_nowait;
                        state =
                              TRA_wait(tdbb, transaction, rpb->rpb_transaction, TRUE);
                        if (wait_flag)
                              transaction->tra_flags &= ~TRA_nowait;

                        if (state == tra_active) {
                              THREAD_EXIT;
                              THREAD_SLEEP(100);      /* milliseconds */
                              THREAD_ENTER;
                              continue;
                        }
                  }

                  /* The snapshot says: transaction was active.  The TIP page says: transaction
                     is committed.  Maybe the transaction was rolled back via a transaction
                     level savepoint.  In that case, the record DPM_get-ed via rpb is already
                     backed out.  Try to refetch that record one more time. */

                  if ((state == tra_committed)
                        && (rpb->rpb_transaction != update_conflict_trans)) {
                        update_conflict_trans = rpb->rpb_transaction;
                        continue;
                  }
                  if (state != tra_dead && !(temp->rpb_flags & rpb_deleted)) {
                        if (!DPM_fetch(tdbb, temp, LCK_write))
                              BUGCHECK(291);    /* msg 291 cannot find record back version */
                        delete_(tdbb, temp, (SLONG) 0, 0);
                  }
                  switch (state) {
                  case tra_committed:
                        // We need to loop waiting in read committed transactions only
                        if (!(transaction->tra_flags & TRA_read_committed))
                              ERR_post(isc_deadlock, isc_arg_gds, isc_update_conflict, 0);
                  case tra_active:
                        return PREPARE_LOCKERR;

                  case tra_limbo:
                        ERR_post(isc_deadlock, isc_arg_gds, isc_trainlim, 0);

                  case tra_dead:
                        break;
                  }
                  break;

            case tra_dead:
            case tra_precommitted:
#ifdef VIO_DEBUG
                  if (debug_flag > DEBUG_READS_INFO)
                        ib_printf
                              ("    record's transaction (%"SLONGFORMAT
                               ") is dead (my TID - %"SLONGFORMAT")\n",
                               rpb->rpb_transaction, transaction->tra_number);
#endif
                  CCH_RELEASE(tdbb, &rpb->rpb_window);
                  break;
            }

            if (state == tra_precommitted) {
                  THREAD_EXIT;
                  THREAD_SLEEP(100);      /* milliseconds */
                  THREAD_ENTER;
            }
            else {
                  VIO_backout(tdbb, rpb, transaction);
            }
      }
      return PREPARE_OK;
}


static BOOLEAN purge(TDBB tdbb, RPB* rpb)
{
/**************************************
 *
 *    p u r g e
 *
 **************************************
 *
 * Functional description
 *    Purge old versions of a fully mature record.  The record is
 *    guaranteed not to be deleted.  Return TRUE if the record
 *    didn't need to be purged or if the purge was done.  Return
 *    FALSE if the purge couldn't happen because somebody else
 *    had the record.
 *
 **************************************/
      DBB dbb;
      LLS staying;
      RPB temp;
      REC record, gc_rec;
      JRD_REL relation;

      SET_TDBB(tdbb);
      dbb = tdbb->tdbb_database;
      CHECK_DBB(dbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE_ALL)
            ib_printf("purge (rpb %"SLONGFORMAT")\n", rpb->rpb_number);
      if (debug_flag > DEBUG_TRACE_ALL_INFO)
            ib_printf
                  ("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line);
#endif

/* Release and re-fetch the page for write.  Make sure it's still the
   same record (give up if not).  Then zap the back pointer and release
   the record.  */

      temp = *rpb;
      relation = rpb->rpb_relation;
      rpb->rpb_record = VIO_gc_record(tdbb, relation);

      VIO_data(tdbb, rpb, reinterpret_cast < blk * >(dbb->dbb_permanent));

      temp.rpb_prior = rpb->rpb_prior;
      gc_rec = record = rpb->rpb_record;
      rpb->rpb_record = temp.rpb_record;

      if (!DPM_get(tdbb, rpb, LCK_write)) {
            gc_rec->rec_flags &= ~REC_gc_active;
            return FALSE;
      }

      rpb->rpb_prior = temp.rpb_prior;

      if (temp.rpb_transaction != rpb->rpb_transaction ||
            temp.rpb_b_line != rpb->rpb_b_line ||
            temp.rpb_b_page != rpb->rpb_b_page || rpb->rpb_b_page == 0) {
            CCH_RELEASE(tdbb, &rpb->rpb_window);
            gc_rec->rec_flags &= ~REC_gc_active;
            return TRUE;
      }

      rpb->rpb_b_page = 0;
      rpb->rpb_b_line = 0;
      rpb->rpb_flags &= ~(rpb_delta | rpb_gc_active);
      CCH_MARK(tdbb, &rpb->rpb_window);
      DPM_rewrite_header(tdbb, rpb);
      CCH_RELEASE(tdbb, &rpb->rpb_window);

      staying = NULL;
      LLS_PUSH(record, &staying);
      garbage_collect(tdbb, &temp, rpb->rpb_page, staying);
      LLS_POP(&staying);
      gc_rec->rec_flags &= ~REC_gc_active;
      VIO_bump_count(tdbb, DBB_purge_count, relation, false);

      return TRUE;
}


static REC replace_gc_record(JRD_REL relation, REC * gc_record, USHORT length)
{
/**************************************
 *
 *    r e p l a c e _ g c _ r e c o r d
 *
 **************************************
 *
 * Functional description
 *    Replace a relation garbage collect record
 *    to accomodate longer length format.
 *
 **************************************/
      VEC vector;
      REC temp;
      vec::iterator rec_ptr, end;

/* V4_MUTEX_LOCK (&relation->rel_mutex); */

      vector = relation->rel_gc_rec;

      for (rec_ptr = vector->begin(), end = vector->end(); rec_ptr < end;
                              ++rec_ptr)
            if (*rec_ptr == *gc_record) {
                  temp = FB_NEW_RPT(*MemoryPool::blk_pool(*gc_record), length) rec;
                  memcpy(temp, *rec_ptr, sizeof(rec) + sizeof(SCHAR)*(*gc_record)->rec_length);
                  delete *rec_ptr;
                  *rec_ptr = temp;
                  // 26 Sep 2002, SKIDDER: Failure to do so causes nasty memory corruption in 
                  // some cases.
                  *gc_record = temp;
/*    V4_MUTEX_UNLOCK (&relation->rel_mutex); */
                  return (REC)*rec_ptr;
            }

/* V4_MUTEX_UNLOCK (&relation->rel_mutex); */
      BUGCHECK(288);                      /* msg 288 garbage collect record disappeared */
      return ((REC) 0);             /* Added to remove compiler warnings */
}


static void replace_record(
                                       TDBB tdbb, RPB * rpb, LLS * stack, JRD_TRA transaction)
{
/**************************************
 *
 *    r e p l a c e _ r e c o r d
 *
 **************************************
 *
 * Functional description
 *    Replace a record and get rid of the old tail, if any.  If requested,
 *    fetch data for the record on the way out.
 *
 **************************************/
      RPB temp;

      SET_TDBB(tdbb);

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE_ALL)
            ib_printf("replace_record (rpb %"SLONGFORMAT", stack, transaction %"
                          SLONGFORMAT")\n",
                          rpb->rpb_number, transaction ? transaction->tra_number : 0);
      if (debug_flag > DEBUG_TRACE_ALL_INFO)
            ib_printf
                  ("   record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT
                   ":%d, prior %p\n",
                   rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction,
                   rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
                   rpb->rpb_f_page, rpb->rpb_f_line, rpb->rpb_prior);
#endif

      temp = *rpb;
      rpb->rpb_flags &=
            ~(rpb_fragment | rpb_incomplete | rpb_chained | rpb_gc_active);
      DPM_update(tdbb, rpb, stack, transaction);
      delete_tail(tdbb, &temp, rpb->rpb_page, 0, 0);

      if ((rpb->rpb_flags & rpb_delta) && !rpb->rpb_prior)
            rpb->rpb_prior = rpb->rpb_record;
}



static void set_system_flag(RPB * rpb, USHORT field_id, SSHORT flag)
{
/**************************************
 *
 *    s e t _ s y s t e m _ f l a g
 *
 **************************************
 *
 * Functional description
 *    Set the value of a particular field to a known binary value.
 *
 **************************************/
      REC record;
      DSC desc1, desc2;

      record = rpb->rpb_record;
      if (EVL_field(0, record, field_id, &desc1))
            return;

      desc2.dsc_dtype = dtype_short;
      desc2.dsc_length = sizeof(SSHORT);
      desc2.dsc_scale = 0;
      desc2.dsc_sub_type = 0;
      desc2.dsc_address = (UCHAR *) & flag;
      MOV_move(&desc2, &desc1);
      CLEAR_NULL(record, field_id);
}


static void update_in_place(
                                          TDBB tdbb,
                                          JRD_TRA transaction, RPB * org_rpb, RPB * new_rpb)
{
/**************************************
 *
 *    u p d a t e _ i n _ p l a c e
 *
 **************************************
 *
 * Functional description
 *    Modify a record in place.  This is used for system transactions
 *    and for multiple modifications of a user record.
 *
 **************************************/
      DBB dbb;
      RPB temp2;
      REC prior, old_data, gc_rec;
      LLS going, staying, *stack;
      JRD_REL relation;
      UCHAR *address;
      SLONG page;
      USHORT line, length, format_number;

      SET_TDBB(tdbb);
      dbb = tdbb->tdbb_database;
      CHECK_DBB(dbb);
      gc_rec = NULL;

#ifdef VIO_DEBUG
      if (debug_flag > DEBUG_TRACE_ALL)
            ib_printf
                  ("update_in_place (transaction %"SLONGFORMAT", org_rpb %"SLONGFORMAT
                   ", new_rpb %"SLONGFORMAT")\n",
                   transaction ? transaction->tra_number : 0, org_rpb->rpb_number,
                   new_rpb ? new_rpb->rpb_number : 0);
      if (debug_flag > DEBUG_TRACE_ALL_INFO)
            ib_printf
                  ("   old record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
                   ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
                   org_rpb->rpb_page, org_rpb->rpb_line, org_rpb->rpb_transaction,
                   org_rpb->rpb_flags, org_rpb->rpb_b_page, org_rpb->rpb_b_line,
                   org_rpb->rpb_f_page, org_rpb->rpb_f_line);
#endif

      stack = &new_rpb->rpb_record->rec_precedence;
      relation = org_rpb->rpb_relation;
      old_data = org_rpb->rpb_record;

/* If the old version has been stored as a delta, things get complicated.  Clearly,
   if we overwrite the current record, the differences from the current version
   becomes meaningless.  What we need to do is replace the old "delta" record
   with an old "complete" record, update in placement, then delete the old
   delta record */

      BOOLEAN refetched = FALSE;
retry:
      if ( (prior = org_rpb->rpb_prior) ) {
            temp2 = *org_rpb;
            temp2.rpb_record = VIO_gc_record(tdbb, relation);
            temp2.rpb_page = org_rpb->rpb_b_page;
            temp2.rpb_line = org_rpb->rpb_b_line;
            if (! DPM_fetch(tdbb, &temp2, LCK_read)) {
                  if (refetched)
                      BUGCHECK(291);       // msg 291 cannot find record back version

            // maybe pre-trigger modified our record - refetch it
                  RefetchRecord(tdbb, org_rpb, transaction);
                  refetched = TRUE;
                  goto retry;
        }
        
            VIO_data(tdbb, &temp2,
                         reinterpret_cast < blk * >(dbb->dbb_permanent));
            gc_rec = temp2.rpb_record;
            temp2.rpb_flags = rpb_chained;
            if (temp2.rpb_prior)
                  temp2.rpb_flags |= rpb_delta;
            temp2.rpb_number = org_rpb->rpb_number;
            DPM_store(tdbb, &temp2, stack, DPM_secondary);

            LLS_PUSH((BLK) temp2.rpb_page, stack);
      }

      if (!DPM_get(tdbb, org_rpb, LCK_write))
            BUGCHECK(186);                /* msg 186 record disappeared */

      if (prior) {
            page = org_rpb->rpb_b_page;
            line = org_rpb->rpb_b_line;
            org_rpb->rpb_b_page = temp2.rpb_page;
            org_rpb->rpb_b_line = temp2.rpb_line;
            org_rpb->rpb_flags &= ~rpb_delta;
            org_rpb->rpb_prior = NULL;
            temp2.rpb_page = page;
            temp2.rpb_line = line;
      }

      address = org_rpb->rpb_address;
      length = org_rpb->rpb_length;
      format_number = org_rpb->rpb_format_number;
      org_rpb->rpb_address = new_rpb->rpb_address;
      org_rpb->rpb_length = new_rpb->rpb_length;
      org_rpb->rpb_format_number = new_rpb->rpb_format_number;

      DEBUG;
      replace_record(tdbb, org_rpb, stack, transaction);
      DEBUG;

      org_rpb->rpb_address = address;
      org_rpb->rpb_length = length;
      org_rpb->rpb_format_number = format_number;
      org_rpb->rpb_undo = old_data;

      if (transaction->tra_flags & TRA_system) {
            /* Garbage collect.  Start by getting all existing old versions (other
               than the immediate two in question). */

            going = staying = NULL;
            list_staying(tdbb, org_rpb, &staying);

            LLS_PUSH(org_rpb->rpb_record, &going);
            LLS_PUSH(new_rpb->rpb_record, &staying);

            BLB_garbage_collect(tdbb, going, staying, org_rpb->rpb_page,
                                          relation);
            IDX_garbage_collect(tdbb, org_rpb, going, staying);

            LLS_POP(&going);
            LLS_POP(&staying);

            while (staying)
                  delete LLS_POP(&staying);
      }

      if (prior) {
            if (!DPM_fetch(tdbb, &temp2, LCK_write))
                  BUGCHECK(291);          /* msg 291 cannot find record back version */
            delete_(tdbb, &temp2, org_rpb->rpb_page, 0);
      }

      if (gc_rec)
            gc_rec->rec_flags &= ~REC_gc_active;
}


static void verb_post(
                                TDBB tdbb,
                                JRD_TRA transaction,
                                RPB * rpb,
                                REC old_data,
                                RPB * new_rpb, BOOLEAN same_tx, BOOLEAN new_ver)
{
/**************************************
 *
 *    v e r b _ p o s t
 *
 **************************************
 *
 * Functional description
 *    Post a record update under verb control to a transaction.
 *    If the previous version of the record was created by
 *    this transaction in a different verb, save the data as well.
 *
 * Input:
 *    old_data:   Only supplied if an in-place operation was performed
 *                      (i.e. update_in_place).
 *    new_rpb:    Only used to pass to garbage_collect_idx.
 *    same_tx:    TRUE if this transaction inserted/updated this record
 *                      and then deleted it.
 *                FALSE in all other cases.
 *
 **************************************/
      VCT action;
      JrdMemoryPool *old_pool;
      REC data;
      UCHAR *p, *q, *end;

      SET_TDBB(tdbb);

      old_pool = tdbb->tdbb_default;
      tdbb->tdbb_default = transaction->tra_pool;

/* Find action block for relation */

      for (action = transaction->tra_save_point->sav_verb_actions; action;
             action = action->vct_next)
            if (action->vct_relation == rpb->rpb_relation)
                  break;

      if (!action) {
            if ( (action = transaction->tra_save_point->sav_verb_free) )
                  transaction->tra_save_point->sav_verb_free = action->vct_next;
            else
                  action = FB_NEW(*tdbb->tdbb_default) vct();
            action->vct_next = transaction->tra_save_point->sav_verb_actions;
            transaction->tra_save_point->sav_verb_actions = action;
            action->vct_relation = rpb->rpb_relation;
      }

      if (!SBM_test(action->vct_records, rpb->rpb_number)) {
            SBM_set(tdbb, &action->vct_records, rpb->rpb_number);
            if (old_data) {
                  /* An update-in-place is being posted to this savepoint, and this
                     savepoint hasn't seen this record before. */

                  data = FB_NEW_RPT(*tdbb->tdbb_default, old_data->rec_length) rec();
                  data->rec_number = rpb->rpb_number;
                  data->rec_length = old_data->rec_length;
                  data->rec_format = old_data->rec_format;
                  if (same_tx)
                        data->rec_flags |= REC_same_tx;
                  for (q = old_data->rec_data, p = data->rec_data, end =
                         q + old_data->rec_length; q < end; q++)
                        *p++ = *q;
                  if (!action->vct_undo)
                        action->vct_undo = new UndoItemTree(tdbb->tdbb_default);
                  action->vct_undo->add(UndoItem(rpb->rpb_number, data));
            }
            else if (same_tx) {
                  /* An insert/update followed by a delete is posted to this savepoint,
                     and this savepoint hasn't seen this record before. */

                  data = FB_NEW_RPT(*tdbb->tdbb_default, 1) rec;
                  data->rec_number = rpb->rpb_number;
                  data->rec_length = 0;
                  if (new_ver)
                        data->rec_flags |= (REC_same_tx | REC_new_version);
                  else
                        data->rec_flags |= REC_same_tx;

                  if (!action->vct_undo)
                        action->vct_undo = new UndoItemTree(tdbb->tdbb_default);
                  action->vct_undo->add(UndoItem(rpb->rpb_number, data));
            }
      }
      else if (same_tx) {
            if (action->vct_undo && action->vct_undo->locate(Firebird::locEqual, rpb->rpb_number)) {
                  /* An insert/update followed by a delete is posted to this savepoint,
                     and this savepoint has already undo for this record. */
                  action->vct_undo->current().rec_data->rec_flags |= REC_same_tx;
            }
            else {
                  /* An insert/update followed by a delete is posted to this savepoint,
                     and this savepoint has seen this record before but it doesn't have
                     undo data. */

                  data = FB_NEW_RPT(*tdbb->tdbb_default, 1) rec();
                  data->rec_number = rpb->rpb_number;
                  data->rec_length = 0;
                  data->rec_flags |= (REC_same_tx | REC_new_version);
                  if (!action->vct_undo)
                        action->vct_undo = new UndoItemTree(tdbb->tdbb_default);
                  action->vct_undo->add(UndoItem(rpb->rpb_number, data));
            }
            if (old_data) {
                  /* The passed old_data will not be used.  Thus, garbage collect. */

                  garbage_collect_idx(tdbb, rpb, new_rpb, old_data);
            }
      }
      else if (old_data) {
            /* We are posting an update-in-place, but the current savepoint has
               already undo data for this record.  The old_data will not be used,
               so make sure we garbage collect before we loose track of the
               in-place-updated record. */

            garbage_collect_idx(tdbb, rpb, new_rpb, old_data);
      }

      tdbb->tdbb_default = old_pool;
}


} // extern "C"

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