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Introduce access/{table.h, relation.h}, for generic functions from heapam.h.
access/heapam contains functions that are very storage specific (say heap_insert() and a lot of lower level functions), and fairly generic infrastructure like relation_open(), heap_open() etc. In the upcoming pluggable storage work we're introducing a layer between table accesses in general and heapam, to allow for different storage methods. For a bit cleaner separation it thus seems advantageous to move generic functions like the aforementioned to their own headers. access/relation.h will contain relation_open() etc, and access/table.h will contain table_open() (formerly known as heap_open()). I've decided for table.h not to include relation.h, but we might change that at a later stage. relation.h already exists in another directory, but the other plausible name (rel.h) also conflicts. It'd be nice if there were a non-conflicting name, but nobody came up with a suggestion. It's possible that the appropriate way to address the naming conflict would be to rename nodes/relation.h, which isn't particularly well named. To avoid breaking a lot of extensions that just use heap_open() etc, table.h has macros mapping the old names to the new ones, and heapam.h includes relation, table.h. That also allows to keep the bulk renaming of existing callers in a separate commit. Author: Andres Freund Discussion: https://postgr.es/m/20190111000539.xbv7s6w7ilcvm7dp@alap3.anarazel.de
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‎src/backend/access/Makefile

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@@ -9,6 +9,6 @@ top_builddir = ../../..
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include $(top_builddir)/src/Makefile.global
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SUBDIRS = brin common gin gist hash heap index nbtree rmgrdesc spgist \
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tablesample transam
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table tablesample transam
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include $(top_srcdir)/src/backend/common.mk

‎src/backend/access/common/Makefile

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@@ -13,6 +13,6 @@ top_builddir = ../../../..
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include $(top_builddir)/src/Makefile.global
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OBJS = bufmask.o heaptuple.o indextuple.o printsimple.o printtup.o \
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reloptions.o scankey.o session.o tupconvert.o tupdesc.o
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relation.o reloptions.o scankey.o session.o tupconvert.o tupdesc.o
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include $(top_srcdir)/src/backend/common.mk

‎src/backend/access/common/relation.c

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/*-------------------------------------------------------------------------
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*
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* relation.c
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* Generic relation related routines.
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*
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* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/backend/access/common/relation.c
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*
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* NOTES
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* This file contains relation_ routines that implement access to relations
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* (tables, indexes, etc). Support that's specific to subtypes of relations
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* should go into their respective files, not here.
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/relation.h"
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#include "access/xact.h"
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#include "catalog/namespace.h"
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#include "miscadmin.h"
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#include "pgstat.h"
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#include "storage/lmgr.h"
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#include "utils/inval.h"
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#include "utils/syscache.h"
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/* ----------------
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* relation_open - open any relation by relation OID
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*
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* If lockmode is not "NoLock", the specified kind of lock is
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* obtained on the relation. (Generally, NoLock should only be
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* used if the caller knows it has some appropriate lock on the
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* relation already.)
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*
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* An error is raised if the relation does not exist.
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*
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* NB: a "relation" is anything with a pg_class entry. The caller is
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* expected to check whether the relkind is something it can handle.
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* ----------------
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*/
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Relation
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relation_open(Oid relationId, LOCKMODE lockmode)
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{
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Relation r;
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Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
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/* Get the lock before trying to open the relcache entry */
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if (lockmode != NoLock)
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LockRelationOid(relationId, lockmode);
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/* The relcache does all the real work... */
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r = RelationIdGetRelation(relationId);
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if (!RelationIsValid(r))
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elog(ERROR, "could not open relation with OID %u", relationId);
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/*
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* If we didn't get the lock ourselves, assert that caller holds one,
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* except in bootstrap mode where no locks are used.
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*/
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Assert(lockmode != NoLock ||
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IsBootstrapProcessingMode() ||
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CheckRelationLockedByMe(r, AccessShareLock, true));
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/* Make note that we've accessed a temporary relation */
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if (RelationUsesLocalBuffers(r))
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MyXactFlags |= XACT_FLAGS_ACCESSEDTEMPREL;
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pgstat_initstats(r);
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return r;
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}
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/* ----------------
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* try_relation_open - open any relation by relation OID
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*
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* Same as relation_open, except return NULL instead of failing
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* if the relation does not exist.
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* ----------------
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*/
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Relation
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try_relation_open(Oid relationId, LOCKMODE lockmode)
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{
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Relation r;
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Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
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/* Get the lock first */
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if (lockmode != NoLock)
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LockRelationOid(relationId, lockmode);
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/*
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* Now that we have the lock, probe to see if the relation really exists
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* or not.
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*/
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if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(relationId)))
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{
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/* Release useless lock */
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if (lockmode != NoLock)
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UnlockRelationOid(relationId, lockmode);
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return NULL;
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}
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/* Should be safe to do a relcache load */
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r = RelationIdGetRelation(relationId);
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if (!RelationIsValid(r))
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elog(ERROR, "could not open relation with OID %u", relationId);
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/* If we didn't get the lock ourselves, assert that caller holds one */
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Assert(lockmode != NoLock ||
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CheckRelationLockedByMe(r, AccessShareLock, true));
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/* Make note that we've accessed a temporary relation */
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if (RelationUsesLocalBuffers(r))
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MyXactFlags |= XACT_FLAGS_ACCESSEDTEMPREL;
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pgstat_initstats(r);
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return r;
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}
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/* ----------------
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* relation_openrv - open any relation specified by a RangeVar
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*
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* Same as relation_open, but the relation is specified by a RangeVar.
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* ----------------
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*/
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Relation
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relation_openrv(const RangeVar *relation, LOCKMODE lockmode)
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{
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Oid relOid;
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/*
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* Check for shared-cache-inval messages before trying to open the
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* relation. This is needed even if we already hold a lock on the
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* relation, because GRANT/REVOKE are executed without taking any lock on
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* the target relation, and we want to be sure we see current ACL
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* information. We can skip this if asked for NoLock, on the assumption
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* that such a call is not the first one in the current command, and so we
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* should be reasonably up-to-date already. (XXX this all could stand to
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* be redesigned, but for the moment we'll keep doing this like it's been
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* done historically.)
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*/
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if (lockmode != NoLock)
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AcceptInvalidationMessages();
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/* Look up and lock the appropriate relation using namespace search */
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relOid = RangeVarGetRelid(relation, lockmode, false);
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/* Let relation_open do the rest */
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return relation_open(relOid, NoLock);
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}
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/* ----------------
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* relation_openrv_extended - open any relation specified by a RangeVar
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*
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* Same as relation_openrv, but with an additional missing_ok argument
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* allowing a NULL return rather than an error if the relation is not
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* found. (Note that some other causes, such as permissions problems,
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* will still result in an ereport.)
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* ----------------
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*/
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Relation
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relation_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
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bool missing_ok)
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{
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Oid relOid;
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/*
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* Check for shared-cache-inval messages before trying to open the
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* relation. See comments in relation_openrv().
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*/
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if (lockmode != NoLock)
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AcceptInvalidationMessages();
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/* Look up and lock the appropriate relation using namespace search */
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relOid = RangeVarGetRelid(relation, lockmode, missing_ok);
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/* Return NULL on not-found */
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if (!OidIsValid(relOid))
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return NULL;
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/* Let relation_open do the rest */
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return relation_open(relOid, NoLock);
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}
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/* ----------------
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* relation_close - close any relation
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*
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* If lockmode is not "NoLock", we then release the specified lock.
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*
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* Note that it is often sensible to hold a lock beyond relation_close;
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* in that case, the lock is released automatically at xact end.
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* ----------------
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*/
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void
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relation_close(Relation relation, LOCKMODE lockmode)
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{
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LockRelId relid = relation->rd_lockInfo.lockRelId;
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Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
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/* The relcache does the real work... */
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RelationClose(relation);
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if (lockmode != NoLock)
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UnlockRelationId(&relid, lockmode);
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}

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