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Commitd70b176

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amcheck: Move common routines into a separate module
Before performing checks on an index, we need to take some safetymeasures that apply to all index AMs. This includes:* verifying that the index can be checked - Only selected AMs aresupported by amcheck (right now only B-Tree). The index has to bevalid and not a temporary index from another session.* changing (and then restoring) user's security context* obtaining proper locks on the index (and table, if needed)* discarding GUC changes from the index functionsUntil now this was implemented in the B-Tree amcheck module, but it'ssomething every AM will have to do. So relocate the code into a newmodule verify_common for reuse.The shared steps are implemented by amcheck_lock_relation_and_check(),receiving the AM-specific verification as a callback. Custom parametersmay be supplied using a pointer.Author: Andrey Borodin <amborodin@acm.org>Reviewed-By: José Villanova <jose.arthur@gmail.com>Reviewed-By: Aleksander Alekseev <aleksander@timescale.com>Reviewed-By: Nikolay Samokhvalov <samokhvalov@gmail.com>Reviewed-By: Andres Freund <andres@anarazel.de>Reviewed-By: Tomas Vondra <tomas@vondra.me>Reviewed-By: Mark Dilger <mark.dilger@enterprisedb.com>Reviewed-By: Peter Geoghegan <pg@bowt.ie>Reviewed-By: Kirill Reshke <reshkekirill@gmail.com>Discussion:https://postgr.es/m/45AC9B0A-2B45-40EE-B08F-BDCF5739D1E1%40yandex-team.ru
1 parentfb9dff7 commitd70b176

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7 files changed

+297
-199
lines changed

7 files changed

+297
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lines changed

‎contrib/amcheck/Makefile

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Original file line numberDiff line numberDiff line change
@@ -3,6 +3,7 @@
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MODULE_big= amcheck
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OBJS =\
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$(WIN32RES)\
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verify_common.o\
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verify_heapam.o\
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verify_nbtree.o
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‎contrib/amcheck/expected/check_btree.out

Lines changed: 2 additions & 2 deletions
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@@ -57,8 +57,8 @@ ERROR: could not open relation with OID 17
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BEGIN;
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CREATE INDEX bttest_a_brin_idx ON bttest_a USING brin(id);
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SELECT bt_index_parent_check('bttest_a_brin_idx');
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ERROR:only B-Tree indexes are supported as targets for verification
61-
DETAIL: Relation "bttest_a_brin_idx" isnot a B-Tree index.
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ERROR:expected "btree" index as targets for verification
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DETAIL: Relation "bttest_a_brin_idx" isa brin index.
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ROLLBACK;
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-- normal check outside of xact
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SELECT bt_index_check('bttest_a_idx');

‎contrib/amcheck/meson.build

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@@ -1,6 +1,7 @@
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# Copyright (c) 2022-2025, PostgreSQL Global Development Group
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amcheck_sources=files(
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'verify_common.c',
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'verify_heapam.c',
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'verify_nbtree.c',
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)

‎contrib/amcheck/verify_common.c

Lines changed: 191 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,191 @@
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/*-------------------------------------------------------------------------
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*
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* verify_common.c
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*Utility functions common to all access methods.
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*
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* Copyright (c) 2016-2025, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* contrib/amcheck/verify_common.c
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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/genam.h"
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#include"access/table.h"
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#include"access/tableam.h"
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#include"verify_common.h"
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#include"catalog/index.h"
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#include"catalog/pg_am.h"
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#include"commands/tablecmds.h"
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#include"utils/guc.h"
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#include"utils/syscache.h"
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staticboolamcheck_index_mainfork_expected(Relationrel);
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/*
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* Check if index relation should have a file for its main relation fork.
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* Verification uses this to skip unlogged indexes when in hot standby mode,
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* where there is simply nothing to verify.
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*
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* NB: Caller should call index_checkable() before calling here.
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*/
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staticbool
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amcheck_index_mainfork_expected(Relationrel)
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{
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if (rel->rd_rel->relpersistence!=RELPERSISTENCE_UNLOGGED||
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!RecoveryInProgress())
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return true;
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ereport(NOTICE,
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(errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
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errmsg("cannot verify unlogged index \"%s\" during recovery, skipping",
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RelationGetRelationName(rel))));
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return false;
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}
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/*
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* Amcheck main workhorse.
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* Given index relation OID, lock relation.
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* Next, take a number of standard actions:
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* 1) Make sure the index can be checked
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* 2) change the context of the user,
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* 3) keep track of GUCs modified via index functions
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* 4) execute callback function to verify integrity.
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*/
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void
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amcheck_lock_relation_and_check(Oidindrelid,
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Oidam_id,
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IndexDoCheckCallbackcheck,
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LOCKMODElockmode,
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void*state)
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{
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Oidheapid;
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Relationindrel;
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Relationheaprel;
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Oidsave_userid;
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intsave_sec_context;
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intsave_nestlevel;
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/*
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* We must lock table before index to avoid deadlocks. However, if the
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* passed indrelid isn't an index then IndexGetRelation() will fail.
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* Rather than emitting a not-very-helpful error message, postpone
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* complaining, expecting that the is-it-an-index test below will fail.
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*
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* In hot standby mode this will raise an error when parentcheck is true.
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*/
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heapid=IndexGetRelation(indrelid, true);
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if (OidIsValid(heapid))
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{
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heaprel=table_open(heapid,lockmode);
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/*
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* Switch to the table owner's userid, so that any index functions are
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* run as that user. Also lock down security-restricted operations
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* and arrange to make GUC variable changes local to this command.
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*/
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GetUserIdAndSecContext(&save_userid,&save_sec_context);
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SetUserIdAndSecContext(heaprel->rd_rel->relowner,
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save_sec_context |SECURITY_RESTRICTED_OPERATION);
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save_nestlevel=NewGUCNestLevel();
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}
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else
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{
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heaprel=NULL;
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/* Set these just to suppress "uninitialized variable" warnings */
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save_userid=InvalidOid;
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save_sec_context=-1;
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save_nestlevel=-1;
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}
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/*
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* Open the target index relations separately (like relation_openrv(), but
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* with heap relation locked first to prevent deadlocking). In hot
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* standby mode this will raise an error when parentcheck is true.
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*
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* There is no need for the usual indcheckxmin usability horizon test
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* here, even in the heapallindexed case, because index undergoing
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* verification only needs to have entries for a new transaction snapshot.
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* (If this is a parentcheck verification, there is no question about
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* committed or recently dead heap tuples lacking index entries due to
115+
* concurrent activity.)
116+
*/
117+
indrel=index_open(indrelid,lockmode);
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119+
/*
120+
* Since we did the IndexGetRelation call above without any lock, it's
121+
* barely possible that a race against an index drop/recreation could have
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* netted us the wrong table.
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*/
124+
if (heaprel==NULL||heapid!=IndexGetRelation(indrelid, false))
125+
ereport(ERROR,
126+
(errcode(ERRCODE_UNDEFINED_TABLE),
127+
errmsg("could not open parent table of index \"%s\"",
128+
RelationGetRelationName(indrel))));
129+
130+
/* Check that relation suitable for checking */
131+
if (index_checkable(indrel,am_id))
132+
check(indrel,heaprel,state,lockmode==ShareLock);
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/* Roll back any GUC changes executed by index functions */
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AtEOXact_GUC(false,save_nestlevel);
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/* Restore userid and security context */
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SetUserIdAndSecContext(save_userid,save_sec_context);
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/*
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* Release locks early. That's ok here because nothing in the called
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* routines will trigger shared cache invalidations to be sent, so we can
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* relax the usual pattern of only releasing locks after commit.
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*/
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index_close(indrel,lockmode);
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if (heaprel)
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table_close(heaprel,lockmode);
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}
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/*
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* Basic checks about the suitability of a relation for checking as an index.
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*
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*
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* NB: Intentionally not checking permissions, the function is normally not
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* callable by non-superusers. If granted, it's useful to be able to check a
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* whole cluster.
157+
*/
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bool
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index_checkable(Relationrel,Oidam_id)
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{
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if (rel->rd_rel->relkind!=RELKIND_INDEX||
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rel->rd_rel->relam!=am_id)
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{
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HeapTupleamtup;
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HeapTupleamtuprel;
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167+
amtup=SearchSysCache1(AMOID,ObjectIdGetDatum(am_id));
168+
amtuprel=SearchSysCache1(AMOID,ObjectIdGetDatum(rel->rd_rel->relam));
169+
ereport(ERROR,
170+
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
171+
errmsg("expected \"%s\" index as targets for verification",NameStr(((Form_pg_am)GETSTRUCT(amtup))->amname)),
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errdetail("Relation \"%s\" is a %s index.",
173+
RelationGetRelationName(rel),NameStr(((Form_pg_am)GETSTRUCT(amtuprel))->amname))));
174+
}
175+
176+
if (RELATION_IS_OTHER_TEMP(rel))
177+
ereport(ERROR,
178+
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
179+
errmsg("cannot access temporary tables of other sessions"),
180+
errdetail("Index \"%s\" is associated with temporary relation.",
181+
RelationGetRelationName(rel))));
182+
183+
if (!rel->rd_index->indisvalid)
184+
ereport(ERROR,
185+
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
186+
errmsg("cannot check index \"%s\"",
187+
RelationGetRelationName(rel)),
188+
errdetail("Index is not valid.")));
189+
190+
returnamcheck_index_mainfork_expected(rel);
191+
}

‎contrib/amcheck/verify_common.h

Lines changed: 31 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,31 @@
1+
/*-------------------------------------------------------------------------
2+
*
3+
* amcheck.h
4+
*Shared routines for amcheck verifications.
5+
*
6+
* Copyright (c) 2016-2025, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
9+
* contrib/amcheck/amcheck.h
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*
11+
*-------------------------------------------------------------------------
12+
*/
13+
#include"storage/bufpage.h"
14+
#include"storage/lmgr.h"
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#include"storage/lockdefs.h"
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#include"utils/relcache.h"
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#include"miscadmin.h"
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/* Typedefs for callback functions for amcheck_lock_relation */
20+
typedefvoid (*IndexCheckableCallback) (Relationindex);
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typedefvoid (*IndexDoCheckCallback) (Relationrel,
22+
Relationheaprel,
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void*state,
24+
boolreadonly);
25+
26+
externvoidamcheck_lock_relation_and_check(Oidindrelid,
27+
Oidam_id,
28+
IndexDoCheckCallbackcheck,
29+
LOCKMODElockmode,void*state);
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31+
externboolindex_checkable(Relationrel,Oidam_id);

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