firebird-mirror/src/jrd/vio.cpp

/*
 *	PROGRAM:	JRD Access Method
 *	MODULE:		vio.cpp
 *	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/common.h"
#include <stdio.h>
#include <string.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/ibase.h"
#include "../jrd/flags.h"
#include "../jrd/ods.h"
#include "../jrd/os/pio.h"
#include "../jrd/btr.h"
#include "../jrd/exe.h"
#include "../jrd/rse.h"
#include "../jrd/rng.h"
#include "../jrd/thd.h"
#include "../jrd/thread_proto.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/sch_proto.h"
#include "../jrd/scl_proto.h"
#include "../jrd/sqz_proto.h"
#include "../jrd/tpc_proto.h"
#include "../jrd/tra_proto.h"
#include "../jrd/vio_proto.h"


using namespace Jrd;

static void check_class(thread_db*, jrd_tra*, record_param*, record_param*, USHORT);
static void check_control(thread_db*);
static bool check_user(thread_db*, const dsc*);
static void delete_record(thread_db*, record_param*, SLONG, JrdMemoryPool*);
static UCHAR* delete_tail(thread_db*, record_param*, SLONG, UCHAR*, const UCHAR*);
static void expunge(thread_db*, record_param*, const jrd_tra*, SLONG);
static void garbage_collect(thread_db*, record_param*, SLONG, RecordStack&);
static void garbage_collect_idx(thread_db*, record_param*, record_param*, Record*);
#ifdef GARBAGE_THREAD
static THREAD_ENTRY_DECLARE garbage_collector(THREAD_ENTRY_PARAM);
#endif
static void list_staying(thread_db*, record_param*, RecordStack&);
#ifdef GARBAGE_THREAD
static void notify_garbage_collector(thread_db*, record_param*);
#endif

const int PREPARE_OK		= 0;
const int PREPARE_CONFLICT	= 1;
const int PREPARE_DELETE	= 2;
const int PREPARE_LOCKERR	= 3;

static int prepare_update(thread_db*, jrd_tra*, SLONG, record_param*, 
						  record_param*, record_param*, PageStack&, bool);

static void purge(thread_db*, record_param*);
static Record* replace_gc_record(jrd_rel*, Record**, USHORT);
static void replace_record(thread_db*, record_param*, PageStack*, const jrd_tra*);
static void set_system_flag(record_param*, USHORT, SSHORT);
static void update_in_place(thread_db*, jrd_tra*, record_param*, record_param*);
static void verb_post(thread_db*, jrd_tra*, record_param*, Record*, record_param*,
					  const bool, const bool);
static void RefetchRecord(thread_db* tdbb, record_param* rpb, jrd_tra*);

/* Pick up relation ids */
#include "../jrd/ini.h"

#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

inline void clearRecordStack(RecordStack& stack)
{
/**************************************
 *
 *	c l e a r R e c o r d S t a c k
 *
 **************************************
 *
 * Functional description
 *	Clears stack, deleting each entry, popped from it.
 *
 **************************************/
	while (stack.hasData()) 
	{
		delete stack.pop();
	}
}

IPTR VIO_savepoint_large(const Savepoint* savepoint, IPTR size)
{
/**************************************
 *
 *	s a v e p o i n t _ l a r g e
 *
 **************************************
 *
 * Functional description
 *	Returns an approximate size in bytes of savepoint in-memory data, i.e. a
 *  measure of how big the current savepoint has gotten.
 *
 *  Notes:
 *
 *  - This routine does not take into account the data allocated to 'vct_undo'.
 *   Why? Because this routine is used to estimate size of transaction-level
 *   savepoint and transaction-level savepoint may not contain undo data as it is
 *   always the first savepoint in transaction.
 *
 *  - Function stops counting when return value gets negative.
 *
 *  - We use IPTR, not SLONG to care of case when user savepoint gets very,
 *   very big on 64-bit machine. Its size may overflow 32 significant bits of
 *   SLONG in this case
 *
 **************************************/
	const VerbAction* verb_actions = savepoint->sav_verb_actions;

	// Iterate all tables changed under this savepoint
	while (verb_actions) {

		// Estimate size used for record backout bitmaps for this table
		if (verb_actions->vct_records) {
			size -= verb_actions->vct_records->approxSize();
		}

		if (size < 0) {
			break;
		}
		verb_actions = verb_actions->vct_next;
	}

	return size;
}

void VIO_backout(thread_db* tdbb, record_param* rpb, const 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 record_param, 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 record_param, 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.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->tdbb_database;
	CHECK_DBB(dbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_WRITES) {
		printf("VIO_backout (record_param %"QUADFORMAT"d, transaction %"SLONGFORMAT
				  ")\n", rpb->rpb_number.getValue(),
				  transaction ? transaction->tra_number : 0);
	}
#endif

	jrd_rel* relation = rpb->rpb_relation;
	VIO_bump_count(tdbb, DBB_backout_count, relation, false);
	RecordStack going, staying;
	Record* data = NULL;
	Record* old_data = NULL;
	Record* gc_rec1 = NULL;
	Record* 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.*/

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

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_WRITES_INFO) {
		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_nr,
			 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_nr != rpb->rpb_transaction_nr)
		&& debug_flag > DEBUG_WRITES_INFO)
	{
		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_nr != rpb->rpb_transaction_nr)
	{
		CCH_RELEASE(tdbb, &temp.rpb_window);
		return;
	}
	if (temp.rpb_flags & rpb_deleted)
		CCH_RELEASE(tdbb, &temp.rpb_window);
	else {
		temp.rpb_record = VIO_gc_record(tdbb, relation);
		VIO_data(tdbb, &temp, dbb->dbb_permanent);
		data = temp.rpb_prior;
		old_data = temp.rpb_record;
		rpb->rpb_prior = temp.rpb_prior;
		gc_rec2 = temp.rpb_record;
		going.push(temp.rpb_record);
	}

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

	record_param 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_nr != rpb->rpb_transaction_nr)
		{
			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, 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_nr != rpb->rpb_transaction_nr)
		&& debug_flag >
		DEBUG_WRITES_INFO)
	{
		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_nr != temp2.rpb_transaction_nr)
	{
		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_record(tdbb, rpb, (SLONG) 0, 0);
		if (!(rpb->rpb_flags & rpb_deleted)) {
			RecordStack empty_staying;
			BLB_garbage_collect(tdbb, going, empty_staying, rpb->rpb_page, relation);
			IDX_garbage_collect(tdbb, rpb, going, empty_staying);
			going.pop();
		}
		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_nr = temp.rpb_transaction_nr;
		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_record(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_record(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.hasData()) 
	{
		going.pop();
	}

	clearRecordStack(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(thread_db* 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.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->tdbb_database;
	CHECK_DBB(dbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE_ALL) {
		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

	const USHORT relation_id = relation->rel_id;
	vcl** ptr = tdbb->tdbb_attachment->att_counts + count_id;

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


bool VIO_chase_record_version(thread_db* tdbb, record_param* rpb, RecordSource* rsb, 
							  jrd_tra* transaction,
							  JrdMemoryPool* pool, bool 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.
 *
 **************************************/
	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE_ALL) {
		printf
			("VIO_chase_record_version (record_param %"QUADFORMAT"d, transaction %"
			 SLONGFORMAT", pool %p)\n",
			 rpb->rpb_number.getValue(), transaction ? transaction->tra_number : 0,
			 (void*) pool);
	}
	if (debug_flag > DEBUG_TRACE_ALL_INFO) {
		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_nr,
			 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 */

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

/* 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_nr >= transaction->tra_oldest_active))
	{
		return true;
	}

	Attachment* 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) {
			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_nr,
				 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_nr, 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_nr, true);

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

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

				/* 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_nr, 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_nr);
				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) {
				printf
					("    record's transaction (%"SLONGFORMAT
					 ") is dead (my TID - %"SLONGFORMAT")\n",
					 rpb->rpb_transaction_nr, 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;
				}
				record_param temp = *rpb;
				if (!(rpb->rpb_flags & rpb_deleted)) {
					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_nr != rpb->rpb_transaction_nr) {
						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) {
				printf
					("    record's transaction (%"SLONGFORMAT
					 ") is in limbo (my TID - %"SLONGFORMAT")\n",
					 rpb->rpb_transaction_nr, 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_nr, 0);
			}

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

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

			if (rsb) {
				const jrd_req* request = tdbb->tdbb_request;
				const irsb_nav* 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 {
				record_param 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_nr != temp.rpb_transaction_nr) {
						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) {
				printf
					("    record's transaction (%"SLONGFORMAT
					 ") is us (my TID - %"SLONGFORMAT")\n",
					 rpb->rpb_transaction_nr, 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) {
				printf
					("    record's transaction (%"SLONGFORMAT
					 ") is committed (my TID - %"SLONGFORMAT")\n",
					 rpb->rpb_transaction_nr, transaction->tra_number);
			}
#endif
			if (rpb->rpb_flags & rpb_deleted) {
				if (rpb->rpb_transaction_nr < 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_nr >= 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_nr);

		/* 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
bool VIO_check_if_updated(thread_db* tdbb, record_param* 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.
 *
 **************************************/
	SET_TDBB(tdbb);

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

	jrd_tra* 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_nr) {
			return false;
		}

		if (rpb->rpb_transaction_nr == transaction->tra_number) {
			return false;
		}

		/* get the state of the given transaction */

		USHORT state = TRA_get_state(tdbb, rpb->rpb_transaction_nr);

		/* 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(thread_db* tdbb, record_param* rpb, JrdMemoryPool* 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 record_param and exits with
 *	an INactive record_param.  Yes, Virginia, getting the data for a
 *	record means losing control of the record.  This turns out
 *	to matter a lot.
 **************************************/
	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_READS)
	{
		printf("VIO_data (record_param %"QUADFORMAT"d, pool %p)\n",
					rpb->rpb_number.getValue(),
					(void*) pool);
	}
	if (debug_flag > DEBUG_READS_INFO)
	{
		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_nr,
				 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. */

	Record* record = VIO_record(tdbb, rpb, 0, pool);
	const Format* format = record->rec_format;

/* If the record is a delta version, start with data from prior record. */
	UCHAR* tail;
	const UCHAR* tail_end;
	UCHAR differences[MAX_DIFFERENCES];
	Record* 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<const char*>(rpb->rpb_address),
							rpb->rpb_length,
							reinterpret_cast<char*>(tail),
							reinterpret_cast<const 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);

			const SCHAR* pIn		= reinterpret_cast<const char*>(rpb->rpb_address);
			SCHAR* pOut		= reinterpret_cast<char*>(tail);
			const SCHAR* const pOutEnd	= reinterpret_cast<const 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 */
	USHORT length;
	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) {
			printf ("VIO_erase (record_param %"QUADFORMAT"d, length %d expected %d)\n", 
				rpb->rpb_number.getValue(), length, format->fmt_length);
		}
	
		if (debug_flag > DEBUG_WRITES_INFO) {
			printf ("   record  %"SLONGFORMAT"d:%d, rpb_trans %"SLONGFORMAT
					   "d, flags %d, back %"SLONGFORMAT"d:%d, fragment %"SLONGFORMAT"d:%d\n",
				rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction_nr, 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(thread_db* tdbb, record_param* 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
 *	record_param and leaves having created an erased
 *	stub. 
 *
 **************************************/
	DSC desc, desc2;
	// Revokee is only 32 bytes. UserId would be truncated.
	SqlIdentifier relation_name, revokee, privilege, procedure_name;

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

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_WRITES)
	{
		printf("VIO_erase (record_param %"QUADFORMAT"d, transaction %"SLONGFORMAT")\n",
				  rpb->rpb_number.getValue(), transaction->tra_number);
	}
	if (debug_flag > DEBUG_WRITES_INFO)
	{
		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_nr,
			 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;
	}

    bool same_tx = false;
	if (rpb->rpb_transaction_nr == 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;
	jrd_rel* 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))
	{
		const jrd_rel* r2;
		const jrd_prc* procedure;
		USHORT id;
	
		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:
			{
			const bool name_defined =
				EVL_field(0, rpb->rpb_record, f_file_name, &desc);
			USHORT rel_flags;
			if (EVL_field(0, rpb->rpb_record, f_file_flags, &desc2) && 
				((rel_flags = MOV_get_long(&desc2, 0)) & FILE_difference))
			{
				if (rel_flags & FILE_backing_up)
					DFW_post_work(transaction, dfw_end_backup, &desc, 0);
				if (name_defined)
					DFW_post_work(transaction, dfw_delete_difference, &desc, 0);
			}
			else
				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;

		default:    /* Shut up compiler warnings */
			break;
		}
	}

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

	record_param temp;
	temp.rpb_transaction_nr = 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;

	const SLONG tid_fetch = rpb->rpb_transaction_nr;
	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)
		{
			printf("   VIO_erase: successfully chained\n");
		}
#endif
	}
	else
	{
		/* Update stub didn't find one page -- do a long, hard update */
		PageStack stack;
		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_nr = 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 propagated */

	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(thread_db* tdbb)
{
/**************************************
 *
 *	V I O _ f i n i
 *
 **************************************
 *
 * Functional description
 *	Shutdown the garbage collector thread.
 *
 **************************************/
	Database* dbb = tdbb->tdbb_database;

	if (dbb->dbb_flags & DBB_garbage_collector)
	{
		event_t* gc_event_fini = dbb->dbb_gc_event_fini;
		/* initialize finalization event */
		ISC_event_init(gc_event_fini, 0, 0);
		SLONG 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();
		ISC_event_wait(1, &gc_event_fini, &count, 0, NULL, 0);
		THREAD_ENTER();
		/* Cleanup finalization event */
		ISC_event_fini(gc_event_fini);
	}
}
#endif


bool VIO_garbage_collect(thread_db* tdbb, record_param* rpb,
	const 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.
 *
 **************************************/
	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE)
	{
		printf("VIO_garbage_collect (record_param %"QUADFORMAT"d, transaction %"
				  SLONGFORMAT")\n",
				  rpb->rpb_number.getValue(), transaction ? transaction->tra_number : 0);
	}
	if (debug_flag > DEBUG_TRACE_INFO)
	{
		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_nr,
			 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;
		}

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

		/* 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_nr >= 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_nr >= transaction->tra_oldest_active ||
				rpb->rpb_b_page == 0)
			{
				return true;
			}

			purge(tdbb, rpb);
		}

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


Record* VIO_gc_record(thread_db* 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.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* 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. */
	vec* vector = relation->rel_gc_rec;
	if (!vector) {
		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. */
	vec::iterator rec_ptr = vector->begin();
	for (const vec::const_iterator end = vector->end();
		rec_ptr != end; ++rec_ptr)
	{
		Record* record = *(Record**) &*rec_ptr;
		if (record && !(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. */
	record_param rpb;
	rpb.rpb_record = 0;
	Record* 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. */

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

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


bool VIO_get(thread_db* tdbb, record_param* rpb, RecordSource* rsb, jrd_tra* transaction, JrdMemoryPool* pool)
{
/**************************************
 *
 *	V I O _ g e t
 *
 **************************************
 *
 * Functional description
 *	Get a specific record from a relation.
 *
 **************************************/
	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_READS) {
		printf("VIO_get (record_param %"QUADFORMAT"d, transaction %"SLONGFORMAT
				  ", pool %p)\n",
				  rpb->rpb_number.getValue(), transaction ? transaction->tra_number : 0,
				  (void*) 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. */

	const USHORT 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) {
		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_nr,
			 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;
}


bool VIO_get_current(
					thread_db* tdbb,
					record_param* rpb, 
					jrd_tra* transaction, 
					JrdMemoryPool* pool, 
					bool 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
 *
 **************************************/
	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE) {
		printf("VIO_get_current (record_param %"QUADFORMAT"d, transaction %"
				  SLONGFORMAT", pool %p)\n",
				  rpb->rpb_number.getValue(), transaction ? transaction->tra_number : 0,
				  (void*) 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) {
			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_nr,
				 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_nr == 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.
		 */

		USHORT state;
		if (transaction->tra_flags & TRA_read_committed) {
			state = TPC_cache_state(tdbb, rpb->rpb_transaction_nr);
		}
		else {
			state =
				TRA_snapshot_state(tdbb, transaction, rpb->rpb_transaction_nr);
		}

		/* 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);
		}
		else if (state == tra_dead) {
			if (transaction->tra_attachment->att_flags & ATT_no_cleanup) {
				return !foreign_key;
			}

			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. */

		const SLONG tid_fetch = rpb->rpb_transaction_nr;

		/* 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_nr, true);
		}
		else {
			const bool wait_flag =
				(transaction->tra_flags & TRA_nowait) == 0;
			transaction->tra_flags |= TRA_nowait;
			state = TRA_wait(tdbb, transaction, rpb->rpb_transaction_nr, 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_nr) {
				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;

		case tra_dead:
			if (transaction->tra_attachment->att_flags & ATT_no_cleanup) {
				return !foreign_key;
			}

			VIO_backout(tdbb, rpb, transaction);
			break;

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

	return !(rpb->rpb_flags & rpb_deleted);
}


#ifdef GARBAGE_THREAD
void VIO_init(thread_db* tdbb)
{
/**************************************
 *
 *	V I O _ i n i t
 *
 **************************************
 *
 * Functional description
 *	Activate the garbage collector thread.
 *
 **************************************/
	Database* dbb = tdbb->tdbb_database;
	Attachment* 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_t* gc_event_init = dbb->dbb_gc_event_init;
		/* Initialize initialization event */
		ISC_event_init(gc_event_init, 0, 0);
		SLONG count = ISC_event_clear(gc_event_init);

		if (gds__thread_start
			(garbage_collector, dbb, THREAD_medium, 0, 0))
		{
			ERR_bugcheck_msg("cannot start thread");
		}
		THREAD_EXIT();
		ISC_event_wait(1, &gc_event_init, &count, 10 * 1000000, NULL, 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(thread_db* tdbb, record_param* 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.
 *
 **************************************/
	const SLONG tid_fetch = rpb->rpb_transaction_nr;
	if ((!DPM_get(tdbb, rpb, LCK_read)) ||
		  (!VIO_chase_record_version
			(tdbb, rpb, NULL, transaction,
			tdbb->getDefaultPool(),
			false)))
	{
		ERR_post(isc_deadlock, isc_arg_gds, isc_update_conflict, 0);
	}
	VIO_data(tdbb, rpb, 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_nr) &&
		// added to check that it was not current transaction,
		// who modified the record. Alex P, 18-Jun-03
		(rpb->rpb_transaction_nr != transaction->tra_number))
	{
		ERR_post(isc_deadlock, isc_arg_gds, isc_update_conflict, 0);
	}
}

void VIO_modify(thread_db* tdbb, record_param* org_rpb, record_param* new_rpb, 
				jrd_tra* transaction)
{
/**************************************
 *
 *	V I O _ m o d i f y
 *
 **************************************
 *
 * Functional description
 *	Modify an existing record.
 *
 **************************************/
	DSC desc1, desc2;

	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_WRITES) {
		printf("VIO_modify (org_rpb %"QUADFORMAT"d, new_rpb %"QUADFORMAT"d, "
				"transaction %"SLONGFORMAT")\n",
				  org_rpb->rpb_number.getValue(), new_rpb->rpb_number.getValue(),
				  transaction ? transaction->tra_number : 0);
	}
	if (debug_flag > DEBUG_WRITES_INFO) {
		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_nr,
			 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_nr = 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 */

	jrd_rel* 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);
			{ // scope
			const USHORT id = MOV_get_long(&desc2, 0);
			DFW_post_work(transaction, dfw_modify_procedure, &desc1, id);
			} // scope
			break;

        case rel_gens:
            EVL_field (0, org_rpb->rpb_record, f_prc_name, &desc1);
            // We won't accept modifying generators.
            DFW_post_work(transaction, dfw_modify_generator, &desc1, 0);
            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;
			
		case rel_files:
			{
				SSHORT new_rel_flags, old_rel_flags;
				EVL_field(0, new_rpb->rpb_record, f_file_name, &desc1);
				if (EVL_field(0, new_rpb->rpb_record, f_file_flags, &desc2) &&
					((new_rel_flags = MOV_get_long(&desc2, 0)) & FILE_difference) &&
					EVL_field(0, org_rpb->rpb_record, f_file_flags, &desc2) &&
					((old_rel_flags = MOV_get_long(&desc2, 0)) != new_rel_flags))
				{
					DFW_post_work(transaction,
						new_rel_flags & FILE_backing_up ?
							dfw_begin_backup :
							dfw_end_backup,
						&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_nr == 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;
	}

	record_param temp;
	PageStack stack;
	if (prepare_update(tdbb, transaction, org_rpb->rpb_transaction_nr, 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_nr = new_rpb->rpb_transaction_nr;
	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;
	}
}


bool VIO_writelock(thread_db* tdbb, record_param* org_rpb, RecordSource* 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
 *
 **************************************/
	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_WRITES) {
		printf("VIO_writelock (org_rpb %"QUADFORMAT"d, transaction %"
				  SLONGFORMAT")\n",
				  org_rpb->rpb_number.getValue(), transaction ? transaction->tra_number : 0);
	}
	if (debug_flag > DEBUG_WRITES_INFO) {
		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_nr,
			 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;
	
	Record* org_record = org_rpb->rpb_record;
	if (!org_record) {
		org_record =
			VIO_record(tdbb, org_rpb, NULL, tdbb->getDefaultPool());
		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;
	}

	record_param temp;
    // 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) {
			// const SLONG tid_fetch = org_rpb->rpb_transaction_nr;
			if ((!DPM_get(tdbb, org_rpb, LCK_read)) ||
				(!VIO_chase_record_version
				 (tdbb, org_rpb, NULL, transaction,
				  tdbb->getDefaultPool(), true)))
			{
				return false;
			}
			VIO_data(tdbb, org_rpb, tdbb->tdbb_request->req_pool);

			org_rpb->rpb_stream_flags &= ~RPB_s_refetch;
			
			// Make sure refetched record still fulfills search condition
			RecordSource* r;
			for (r = rsb; r && r->rsb_type != rsb_boolean ; r = r->rsb_next); // empty loop body
			if (r && !EVL_boolean(tdbb, (jrd_nod*) r->rsb_arg[0]))
				return false;
		}

		// jrd_rel* relation = org_rpb->rpb_relation;


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

		PageStack stack;
		switch (prepare_update(tdbb, transaction, org_rpb->rpb_transaction_nr,
					org_rpb, &temp, 0, stack, true))
		{
			case PREPARE_CONFLICT:
				org_rpb->rpb_stream_flags |= RPB_s_refetch;
				continue;
			case PREPARE_LOCKERR:
				// We got some kind of locking error (deadlock, timeout or lock_conflict)
				// Error details should be stuffed into status vector at this point
				ERR_punt();
			case PREPARE_DELETE:
				return false;
		}

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

		org_rpb->rpb_transaction_nr = 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;
	}
}


bool VIO_next_record(thread_db* tdbb,
						record_param* rpb,
						RecordSource* rsb,
						jrd_tra* transaction,
						JrdMemoryPool* pool, bool backwards, bool onepage)
{
/**************************************
 *
 *	V I O _ n e x t _ r e c o r d
 *
 **************************************
 *
 * Functional description
 *	Get the next record in a record stream.
 *
 **************************************/
	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. */

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

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE) {
		printf("VIO_next_record (record_param %"QUADFORMAT"d, transaction %"
				  SLONGFORMAT", pool %p)\n",
				  rpb->rpb_number.getValue(), transaction ? transaction->tra_number : 0,
				  (void*) pool);
	}
	if (debug_flag > DEBUG_TRACE_INFO) {
		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_nr,
			 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) {
		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_nr,
			 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;
}


Record* VIO_record(thread_db* tdbb, record_param* rpb, const Format* format, 
				   JrdMemoryPool *pool)
{
/**************************************
 *
 *	V I O _ r e c o r d
 *
 **************************************
 *
 * Functional description
 *	Allocate a record block big enough for a given format.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->tdbb_database;
	CHECK_DBB(dbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE) {
		printf("VIO_record (record_param %"QUADFORMAT"d, format %d, pool %p)\n",
				  rpb->rpb_number.getValue(), format ? format->fmt_version : 0,
				  (void*) pool);
	}
#endif

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

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

	Record* record = rpb->rpb_record;
	if (!record) {
		if (!pool) {
			pool = dbb->dbb_permanent;
		}
		record = rpb->rpb_record = FB_NEW_RPT(*pool, format->fmt_length) Record(*pool);
		record->rec_length = format->fmt_length;
	}
	else if (record->rec_length < format->fmt_length) {
		Record* const 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(rpb->rpb_record->rec_pool, format->fmt_length) 
				Record(rpb->rpb_record->rec_pool);
			memcpy(record, rpb->rpb_record, sizeof(Record) + 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(thread_db* 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.
 *
 **************************************/
	SET_TDBB(tdbb);

	Savepoint* sav_point = FB_NEW(*transaction->tra_pool) Savepoint();
	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(thread_db* tdbb, record_param* rpb, jrd_tra* transaction)
{
/**************************************
 *
 *	V I O _ s t o r e
 *
 **************************************
 *
 * Functional description
 *	Store a new record.
 *
 **************************************/
	DSC desc, desc2;

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

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_WRITES) {
		printf("VIO_store (record_param %"QUADFORMAT"d, transaction %"SLONGFORMAT
				  ")\n", rpb->rpb_number.getValue(),
				  transaction ? transaction->tra_number : 0);
	}
#endif

	transaction->tra_flags |= TRA_write;
	jrd_rel* 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);
			{ // scope
			const USHORT id = MOV_get_long(&desc2, 0);
			DFW_post_work(transaction, dfw_create_procedure, &desc, id);
			} // scope
			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:
			{
			const bool name_defined =
				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 {
				USHORT rel_flags;
				if (EVL_field(0, rpb->rpb_record, f_file_flags, &desc2)
					&& ((rel_flags = MOV_get_long(&desc2, 0)) & FILE_difference))
				{
					if (name_defined) {
						DFW_post_work(transaction, dfw_add_difference, &desc, 0);
					}
					if (rel_flags & FILE_backing_up)
					{
						DFW_post_work(transaction, dfw_begin_backup, &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);
			{ // scope
			const USHORT id = MOV_get_long(&desc2, 0);
			DFW_post_work(transaction, dfw_grant, &desc, id);
			} // scope
			break;

		default:    /* Shut up compiler warnings */
			break;
		}
	}

	rpb->rpb_b_page = 0;
	rpb->rpb_b_line = 0;
	rpb->rpb_flags = 0;
	rpb->rpb_transaction_nr = transaction->tra_number;
	rpb->rpb_window.win_flags = 0;
	rpb->rpb_record->rec_precedence.push(-rpb->rpb_transaction_nr);
	DPM_store(tdbb, rpb, rpb->rpb_record->rec_precedence, DPM_primary);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_WRITES_INFO) {
		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_nr,
			 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;
	}
}


bool VIO_sweep(thread_db* tdbb, jrd_tra* transaction)
{
/**************************************
 *
 *	V I O _ s w e e p
 *
 **************************************
 *
 * Functional description
 *	Make a garbage collection pass.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->tdbb_database;

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE) {
		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);
	record_param rpb;
	rpb.rpb_record = NULL;
	rpb.rpb_stream_flags = 0;
	rpb.rpb_window.win_flags = WIN_large_scan;
	
	jrd_rel* relation = 0; // wasn't initialized: memory problem in catch() part.
	vec* vector = 0;

	try {

		for (size_t 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.setValue(BOF_NUMBER);
				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) {
						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(thread_db* 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.
 *
 **************************************/
	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE) {
		printf("VIO_verb_cleanup (transaction %"SLONGFORMAT")\n",
				  transaction ? transaction->tra_number : 0);
	}
#endif
	if (transaction->tra_flags & TRA_system) {
		return;
	}

	Savepoint* sav_point = transaction->tra_save_point;
	if (!sav_point) 
	{
		return;
	}

	Jrd::ContextPoolHolder context(tdbb, 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;
		}
	}

	record_param rpb;
	VerbAction* action;
	while ( (action = sav_point->sav_verb_actions) ) {
		sav_point->sav_verb_actions = action->vct_next;
		jrd_rel* relation = action->vct_relation;
		if (sav_point->sav_verb_count || transaction->tra_save_point) {
			rpb.rpb_relation = relation;
			rpb.rpb_number.setValue(BOF_NUMBER);
			rpb.rpb_record = NULL;
			rpb.rpb_window.win_flags = 0;
			rpb.rpb_transaction_nr = transaction->tra_number;

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

				RecordBitmap::Accessor accessor(action->vct_records);
				if (accessor.getFirst()) do	{
					rpb.rpb_number.setValue(accessor.current());
					if (!DPM_get(tdbb, &rpb, LCK_write)) {
						BUGCHECK(186);	/* msg 186 record disappeared */
					}
					if (rpb.rpb_flags & rpb_delta) {
						VIO_data(tdbb, &rpb, tdbb->getDefaultPool());
					}
					else {
						CCH_RELEASE(tdbb, &rpb.rpb_window);
					}
					if (rpb.rpb_transaction_nr != transaction->tra_number) {
						BUGCHECK(185);	/* msg 185 wrong record version */
					}
					if (!action->vct_undo ||
						!action->vct_undo->locate(Firebird::locEqual, rpb.rpb_number.getValue()))
					{
						VIO_backout(tdbb, &rpb, transaction);
					}
					else {
						Record* record = action->vct_undo->current().rec_data;
						const bool same_tx = (record->rec_flags & REC_same_tx) != 0;

						/* 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, tdbb->getDefaultPool());
								}
								else {
									CCH_RELEASE(tdbb, &rpb.rpb_window);
								}

								VIO_backout(tdbb, &rpb, transaction);
							}
						}
						if (record->rec_length != 0) {
							Record* dead_record = rpb.rpb_record;
							record_param 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, tdbb->getDefaultPool());
							}
							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;
						}
					}
				} while (accessor.getNext());
			}
			else {
				/* This savepoint needs to be posted to the previous savepoint. */

				RecordBitmap::Accessor accessor(action->vct_records);
				if (accessor.getFirst()) do
				{
					rpb.rpb_number.setValue(accessor.current());
					if (!action->vct_undo ||
						!action->vct_undo->locate(Firebird::locEqual, rpb.rpb_number.getValue()))
					{
						verb_post(tdbb, transaction, &rpb, 0, 0, false, false);
					}
					else {
						/* 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* record = action->vct_undo->current().rec_data;
						const bool same_tx =
							(record->rec_flags & REC_same_tx) != 0;
						const bool new_ver =
							(record->rec_flags & REC_new_version) != 0;
						if (record->rec_length != 0) {
							record_param 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);
						}
					}
				} while (accessor.getNext());
			}

			if (rpb.rpb_record) {
				delete rpb.rpb_record;
			}
		}
		delete 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;
		}
		delete action;
	}

	delete 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
	}
}



void VIO_merge_proc_sav_points(
							   thread_db* tdbb,
							   jrd_tra* transaction, Savepoint** 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.
 *
 **************************************/
	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 (Savepoint* sav_point = *sav_point_list; sav_point;
		 sav_point = sav_point->sav_next)
	{
		Savepoint* const sav_next = sav_point->sav_next;
		const SLONG 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 = FB_NEW(*transaction->tra_pool) Savepoint();
		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(
						thread_db* tdbb,
						jrd_tra* transaction,
						record_param* old_rpb, record_param* 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.
 *
 **************************************/
	SET_TDBB(tdbb);

	DSC desc1, desc2;
	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* 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(thread_db* 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.
 *
 **************************************/
	SET_TDBB(tdbb);

	Attachment* attachment = tdbb->tdbb_attachment;

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


static bool check_user(thread_db* tdbb, const dsc* desc)
{
/**************************************
 *
 *	c h e c k _ u s e r
 *
 **************************************
 *
 * Functional description
 *	Validate string against current user name.
 *
 **************************************/
	SET_TDBB(tdbb);

	const TEXT* p = (TEXT *) desc->dsc_address;
	const TEXT* const end = p + desc->dsc_length;
	const TEXT* 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_record(thread_db* tdbb, record_param* 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.
 *
 **************************************/
	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_WRITES) {
		printf("delete_record (record_param %"QUADFORMAT"d, prior_page %"SLONGFORMAT", pool %p)\n",
				  rpb->rpb_number.getValue(), prior_page,
				  (void*) pool);
	}
	if (debug_flag > DEBUG_WRITES_INFO) {
		printf
			("   delete_record record  %"SLONGFORMAT":%d, rpb_trans %"SLONGFORMAT
			 ", flags %d, back %"SLONGFORMAT":%d, fragment %"SLONGFORMAT":%d\n",
			 rpb->rpb_page, rpb->rpb_line, rpb->rpb_transaction_nr,
			 rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
			 rpb->rpb_f_page, rpb->rpb_f_line);
	}
#endif
	UCHAR* tail;
	const UCHAR* tail_end;
	UCHAR differences[MAX_DIFFERENCES];
	Record* record = 0;
	const Record* prior = 0;
	if (!pool || (rpb->rpb_flags & rpb_deleted)) {
		prior = NULL;
		tail_end = tail = NULL;
	}
	else {
		record = VIO_record(tdbb, rpb, 0, pool);
		prior = rpb->rpb_prior;
		if (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<const char*>(rpb->rpb_address), rpb->rpb_length,
			   reinterpret_cast<char*>(tail),
			   reinterpret_cast<const char*>(tail_end)));
		rpb->rpb_prior = (rpb->rpb_flags & rpb_delta) ? record : 0;
	}

	record_param 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<const char*>(differences),
							  reinterpret_cast<const char*>(tail));
	}
}


static UCHAR* delete_tail(
						  thread_db* tdbb,
						  record_param* rpb,
						  SLONG prior_page, UCHAR* tail, const 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) {
		printf
			("delete_tail (record_param %"QUADFORMAT"d, prior_page %"SLONGFORMAT", tail %p, tail_end %p)\n",
			 rpb->rpb_number.getValue(), prior_page, tail, tail_end);
	}
	if (debug_flag > DEBUG_WRITES_INFO) {
		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_nr,
			 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<const char*>(rpb->rpb_address),
				   rpb->rpb_length, reinterpret_cast<char*>(tail),
				   reinterpret_cast<const char*>(tail_end)));
		}
		DPM_delete(tdbb, rpb, prior_page);
		prior_page = rpb->rpb_page;
	}

	return tail;
}


static void expunge(thread_db* tdbb, record_param* rpb,
	const 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.
 *
 **************************************/
	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_WRITES) {
		printf("expunge (record_param %"QUADFORMAT"d, transaction %"SLONGFORMAT
				  ", prior_page %"SLONGFORMAT")\n",
				  rpb->rpb_number.getValue(), 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) {
		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_nr,
			 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_nr >= transaction->tra_oldest_active)
	{
		CCH_RELEASE(tdbb, &rpb->rpb_window);
		return;
	}

	delete_record(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. */

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


static void garbage_collect(thread_db* tdbb,
							record_param* rpb, SLONG prior_page, 
							RecordStack& 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 record_param, 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) {
		printf("garbage_collect (record_param %"QUADFORMAT"d, prior_page %"SLONGFORMAT
				  ", staying)\n",
				  rpb->rpb_number.getValue(), prior_page);
	}
	if (debug_flag > DEBUG_WRITES_INFO) {
		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_nr,
			 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. */

	RecordStack going;

	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_record(tdbb, rpb, prior_page, tdbb->getDefaultPool());
		if (rpb->rpb_record) {
			going.push(rpb->rpb_record);
		}
#ifdef SUPERSERVER
		/* Don't monopolize the server while chasing long
		   back version chains. */

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

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

	clearRecordStack(going);
}


static void garbage_collect_idx(
								thread_db* tdbb,
								record_param* org_rpb, record_param* new_rpb,
								Record* 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.
 *
 **************************************/
	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). */

	RecordStack going, staying;
	list_staying(tdbb, org_rpb, staying);

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

	going.push(old_data ? old_data : org_rpb->rpb_record);

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

	going.pop();

	clearRecordStack(staying);
}


#ifdef GARBAGE_THREAD
static THREAD_ENTRY_DECLARE garbage_collector(THREAD_ENTRY_PARAM arg)
{
/**************************************
 *
 *	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.
 *
 **************************************/
	Database* dbb = (Database*)arg;
	THREAD_ENTER();
	CHECK_DBB(dbb);
	event_t* gc_event = dbb->dbb_gc_event;
	record_param rpb;
	MOVE_CLEAR(&rpb, sizeof(record_param));
	ISC_STATUS_ARRAY status_vector;
	MOVE_CLEAR(status_vector, sizeof(status_vector));
	jrd_rel* relation = 0;
	jrd_tra* 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. */
	thread_db thd_context, *tdbb;
	JRD_set_thread_data(tdbb, thd_context);
	tdbb->tdbb_database = dbb;
	tdbb->setDefaultPool(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. */
	bool found = false, flush = false;
	
	try {
		ISC_event_init(gc_event, 0, 0);

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

		tdbb->tdbb_attachment = FB_NEW(*dbb->dbb_permanent) Attachment(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) {

			SLONG 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) {
				Attachment* 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, NULL, 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 (ULONG 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;
					SLONG 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.setValue((dp_sequence * dbb->dbb_max_records) - 1);
						const RecordNumber last(rpb.rpb_number.getValue() + 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) {
								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 */
						delete 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) {
				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, FLUSH_SWEEP, 0);
						}
						continue;
					}
					dbb->dbb_flags &= ~DBB_gc_active;
					THREAD_EXIT();
					int timeout = ISC_event_wait(1, &gc_event, &count, 
												 10 * 1000000, NULL, 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);

		JRD_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 void list_staying(thread_db* tdbb, record_param* rpb, RecordStack& 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.
 *
 **************************************/
	SET_TDBB(tdbb);

	Record* data = rpb->rpb_prior;
	ULONG next_page = rpb->rpb_page;
	USHORT next_line = rpb->rpb_line;
	USHORT max_depth = 0;
	USHORT 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. */

		record_param temp = *rpb;
		depth = 0;

		/* If the entire record disappeared, then there is nothing staying. */
		if (!DPM_fetch(tdbb, &temp, LCK_read)) {
			clearRecordStack(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)
		{
			clearRecordStack(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) {
				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, tdbb->getDefaultPool());
				staying.push(temp.rpb_record);
				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.hasData()) 
		{
			delete staying.pop();
		}
	}
}


#ifdef GARBAGE_THREAD
static void notify_garbage_collector(thread_db* tdbb, record_param* 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.
 *
 **************************************/
	Database* 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->getDefaultPool();

	tdbb->setDefaultPool(dbb->dbb_permanent);
	const SLONG dp_sequence = rpb->rpb_number.getValue() / dbb->dbb_max_records;
	SBM_set(tdbb, &relation->rel_gc_bitmap, dp_sequence);
	tdbb->setDefaultPool(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(	thread_db*		tdbb,
							jrd_tra*		transaction,
							SLONG			commit_tid_read,
							record_param*	rpb,
							record_param*	temp,
							record_param*	new_rpb,
							PageStack&		stack,
							bool			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.
 *
 **************************************/
	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE_ALL) {
		printf
			("prepare_update (transaction %"SLONGFORMAT
			 ", commit_tid read %"SLONGFORMAT", record_param %"QUADFORMAT"d, ",
			 transaction ? transaction->tra_number : 0, commit_tid_read,
			 rpb ? rpb->rpb_number.getValue() : 0);
		printf(" temp_rpb %"QUADFORMAT"d, new_rpb %"QUADFORMAT"d, stack)\n",
				  temp ? temp->rpb_number.getValue() : 0,
				  new_rpb ? new_rpb->rpb_number.getValue() : 0);
	}
	if (debug_flag > DEBUG_TRACE_ALL_INFO) {
		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_nr,
			 rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
			 rpb->rpb_f_page, rpb->rpb_f_line, (void*) 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* 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 */
	UCHAR differences[MAX_DIFFERENCES];
	if (new_rpb)
	{
		const USHORT l = SQZ_differences(
							reinterpret_cast<const 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)
		{
			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. */
	record_param org_rpb;
	SLONG update_conflict_trans = -1;
	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_record(tdbb, temp, (SLONG) 0, 0);
				return PREPARE_DELETE;
			}
		}


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

		/* 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) {
				printf
					("    record's transaction (%"SLONGFORMAT
					 ") is committed (my TID - %"SLONGFORMAT")\n",
					 rpb->rpb_transaction_nr, 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_record(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_nr))
			{
				CCH_RELEASE(tdbb, &rpb->rpb_window);
				if (!DPM_fetch(tdbb, temp, LCK_write)) {
					BUGCHECK(291);	/* msg 291 cannot find record back version */
				}
				delete_record(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) {
				printf
					("    record's transaction (%"SLONGFORMAT
					 ") is us (my TID - %"SLONGFORMAT")\n",
					 rpb->rpb_transaction_nr, transaction->tra_number);
			}

#endif
			if (rpb->rpb_b_page != temp->rpb_b_page ||
				rpb->rpb_b_line != temp->rpb_b_line ||
				rpb->rpb_transaction_nr != temp->rpb_transaction_nr ||
				(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))
				{
					record_param temp2 = *temp;
					if (!DPM_fetch(tdbb, &temp2, LCK_write)) {
						BUGCHECK(291);	/* msg 291 cannot find record back version */
					}
					delete_record(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_nr = rpb->rpb_transaction_nr;
				DPM_store(tdbb, temp, stack, DPM_secondary);
				continue;
			}
			stack.push(temp->rpb_page);
			return PREPARE_OK;

		case tra_active:
		case tra_limbo:
#ifdef VIO_DEBUG
			if (debug_flag > DEBUG_READS_INFO) {
				printf
					("    record's transaction (%"SLONGFORMAT
					 ") is %s (my TID - %"SLONGFORMAT")\n",
					 rpb->rpb_transaction_nr,
					 (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_nr, true);
			}
			else {
				const bool wait_flag = (transaction->tra_flags & TRA_nowait) == 0;
				transaction->tra_flags |= TRA_nowait;
				state =
					TRA_wait(tdbb, transaction, rpb->rpb_transaction_nr, 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_nr != update_conflict_trans))
			{
				update_conflict_trans = rpb->rpb_transaction_nr;
				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_record(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;
			} // switch (state)
			break;

		case tra_dead:
		case tra_precommitted:
#ifdef VIO_DEBUG
			if (debug_flag > DEBUG_READS_INFO) {
				printf
					("    record's transaction (%"SLONGFORMAT
					 ") is dead (my TID - %"SLONGFORMAT")\n",
					 rpb->rpb_transaction_nr, 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 void purge(thread_db* tdbb, record_param* 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.
 *	But the function was made void since nobody checks its return value.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->tdbb_database;
	CHECK_DBB(dbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE_ALL) {
		printf("purge (record_param %"QUADFORMAT"d)\n", rpb->rpb_number.getValue());
	}
	if (debug_flag > DEBUG_TRACE_ALL_INFO) {
		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_nr,
			 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.  */

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

	VIO_data(tdbb, rpb, dbb->dbb_permanent);

	temp.rpb_prior = rpb->rpb_prior;
	Record* record = rpb->rpb_record;
	Record* gc_rec = 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_nr != rpb->rpb_transaction_nr ||
		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);

	RecordStack staying;
	staying.push(record);
	garbage_collect(tdbb, &temp, rpb->rpb_page, staying);
	gc_rec->rec_flags &= ~REC_gc_active;
	VIO_bump_count(tdbb, DBB_purge_count, relation, false);

	return; // true;
}


static Record* replace_gc_record(jrd_rel* relation, Record** 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.
 *
 **************************************/

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

	vec* vector = relation->rel_gc_rec;
	vec::iterator rec_ptr, end;
	for (rec_ptr = vector->begin(), end = vector->end(); rec_ptr < end;
					++rec_ptr)
	{
		if (*rec_ptr == *gc_record) {
			Record* temp = FB_NEW_RPT((*gc_record)->rec_pool, length) Record((*gc_record)->rec_pool);
			memcpy(temp, *rec_ptr, sizeof(Record) + 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 (Record*)*rec_ptr;
		}
	}

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


static void replace_record(thread_db*		tdbb, 
						   record_param*	rpb, 
						   PageStack*		stack,
						   const 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.
 *
 **************************************/
	SET_TDBB(tdbb);

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE_ALL) {
		printf("replace_record (record_param %"QUADFORMAT"d, transaction %"
				  SLONGFORMAT")\n",
				  rpb->rpb_number.getValue(), transaction ? transaction->tra_number : 0);
	}
	if (debug_flag > DEBUG_TRACE_ALL_INFO) {
		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_nr,
			 rpb->rpb_flags, rpb->rpb_b_page, rpb->rpb_b_line,
			 rpb->rpb_f_page, rpb->rpb_f_line, (void*) rpb->rpb_prior);
	}
#endif

	record_param 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(record_param* 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.
 *
 **************************************/
	dsc desc1;

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

	dsc desc2;
	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(
							thread_db* tdbb,
							jrd_tra* transaction, record_param* org_rpb, record_param* 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.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->tdbb_database;
	CHECK_DBB(dbb);
	Record* gc_rec = NULL;

#ifdef VIO_DEBUG
	if (debug_flag > DEBUG_TRACE_ALL) {
		printf
			("update_in_place (transaction %"SLONGFORMAT", org_rpb %"QUADFORMAT"d, "
			 "new_rpb %"QUADFORMAT"d)\n",
			 transaction ? transaction->tra_number : 0, org_rpb->rpb_number.getValue(),
			 new_rpb ? new_rpb->rpb_number.getValue() : 0);
	}
	if (debug_flag > DEBUG_TRACE_ALL_INFO) {
		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_nr,
			 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

	PageStack& stack = new_rpb->rpb_record->rec_precedence;
	jrd_rel* relation = org_rpb->rpb_relation;
	Record* 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 */

	record_param temp2;
	Record* prior;
	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)) {
			BUGCHECK(291);	 // msg 291 cannot find record back version
        }
        
		VIO_data(tdbb, &temp2, 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);

		stack.push(temp2.rpb_page);
	}

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

	if (prior) {
		const SLONG page = org_rpb->rpb_b_page;
		const USHORT 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;
	}

	UCHAR* address = org_rpb->rpb_address;
	const USHORT length = org_rpb->rpb_length;
	const USHORT 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). */

		RecordStack staying;
		list_staying(tdbb, org_rpb, staying);
		staying.push(new_rpb->rpb_record);
		
		RecordStack going;
		going.push(org_rpb->rpb_record);

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

		staying.pop();
		clearRecordStack(staying);
	}

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

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


static void verb_post(
					  thread_db* tdbb,
					  jrd_tra* transaction,
					  record_param* rpb,
					  Record* old_data,
					  record_param* new_rpb,
					  const bool same_tx, const bool 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.
 *
 **************************************/
#pragma FB_COMPILER_MESSAGE("Out-of-memory condition in this function corrupts database. And it is likely due to huge amounts of allocations")
	SET_TDBB(tdbb);

	Jrd::ContextPoolHolder context(tdbb, transaction->tra_pool);

/* Find action block for relation */
	VerbAction* action;
	for (action = transaction->tra_save_point->sav_verb_actions; action;
		 action = action->vct_next)
	{
		if (action->vct_relation == rpb->rpb_relation) {
			break;
		}
	}

	if (!action) {
		action = FB_NEW(*tdbb->getDefaultPool()) VerbAction();
		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 (!RecordBitmap::test(action->vct_records, rpb->rpb_number.getValue())) {
		RBM_SET(tdbb->getDefaultPool(), &action->vct_records, rpb->rpb_number.getValue());
		if (old_data) {
			/* An update-in-place is being posted to this savepoint, and this
			   savepoint hasn't seen this record before. */

			Record* data = FB_NEW_RPT(*tdbb->getDefaultPool(), old_data->rec_length) Record(*tdbb->getDefaultPool());
			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;
			}
			UCHAR* p = data->rec_data;
			const UCHAR* q = old_data->rec_data;
			for (const UCHAR* const end = q + old_data->rec_length; q < end; q++)
			{
				*p++ = *q;
			}
			if (!action->vct_undo) {
				action->vct_undo = new UndoItemTree(tdbb->getDefaultPool());
			}
			action->vct_undo->add(UndoItem(rpb->rpb_number.getValue(), 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. */

			Record* data = FB_NEW_RPT(*tdbb->getDefaultPool(), 1) Record(*tdbb->getDefaultPool());
			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->getDefaultPool());
			}
			action->vct_undo->add(UndoItem(rpb->rpb_number.getValue(), data));
		}
	}
	else if (same_tx) {
		if (action->vct_undo && action->vct_undo->locate(rpb->rpb_number.getValue())) {
			/* 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. */

			Record* data = FB_NEW_RPT(*tdbb->getDefaultPool(), 1) Record(*tdbb->getDefaultPool());
			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->getDefaultPool());
			}
			action->vct_undo->add(UndoItem(rpb->rpb_number.getValue(), 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 lose track of the
		   in-place-updated record. */

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