mirror of https://github.com/postgres/postgres
Before performing checks on an index, we need to take some safety measures that apply to all index AMs. This includes: * verifying that the index can be checked - Only selected AMs are supported by amcheck (right now only B-Tree). The index has to be valid 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 functions Until now this was implemented in the B-Tree amcheck module, but it's something every AM will have to do. So relocate the code into a new module verify_common for reuse. The shared steps are implemented by amcheck_lock_relation_and_check(), receiving the AM-specific verification as a callback. Custom parameters may 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.rupull/208/head
Tomas Vondra
6 months ago
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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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static bool amcheck_index_mainfork_expected(Relation rel); |
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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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static bool |
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amcheck_index_mainfork_expected(Relation rel) |
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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(Oid indrelid, |
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Oid am_id, |
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IndexDoCheckCallback check, |
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LOCKMODE lockmode, |
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void *state) |
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{ |
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Oid heapid; |
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Relation indrel; |
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Relation heaprel; |
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Oid save_userid; |
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int save_sec_context; |
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int save_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 |
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* concurrent activity.) |
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*/ |
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indrel = index_open(indrelid, lockmode); |
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/*
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* Since we did the IndexGetRelation call above without any lock, it's |
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* 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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*/ |
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if (heaprel == NULL || heapid != IndexGetRelation(indrelid, false)) |
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ereport(ERROR, |
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(errcode(ERRCODE_UNDEFINED_TABLE), |
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errmsg("could not open parent table of index \"%s\"", |
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RelationGetRelationName(indrel)))); |
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/* Check that relation suitable for checking */ |
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if (index_checkable(indrel, am_id)) |
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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. |
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*/ |
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bool |
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index_checkable(Relation rel, Oid am_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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HeapTuple amtup; |
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HeapTuple amtuprel; |
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amtup = SearchSysCache1(AMOID, ObjectIdGetDatum(am_id)); |
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amtuprel = SearchSysCache1(AMOID, ObjectIdGetDatum(rel->rd_rel->relam)); |
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ereport(ERROR, |
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(errcode(ERRCODE_FEATURE_NOT_SUPPORTED), |
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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.", |
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RelationGetRelationName(rel), NameStr(((Form_pg_am) GETSTRUCT(amtuprel))->amname)))); |
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} |
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if (RELATION_IS_OTHER_TEMP(rel)) |
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ereport(ERROR, |
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(errcode(ERRCODE_FEATURE_NOT_SUPPORTED), |
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errmsg("cannot access temporary tables of other sessions"), |
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errdetail("Index \"%s\" is associated with temporary relation.", |
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RelationGetRelationName(rel)))); |
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if (!rel->rd_index->indisvalid) |
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ereport(ERROR, |
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(errcode(ERRCODE_FEATURE_NOT_SUPPORTED), |
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errmsg("cannot check index \"%s\"", |
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RelationGetRelationName(rel)), |
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errdetail("Index is not valid."))); |
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return amcheck_index_mainfork_expected(rel); |
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} |
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@ -0,0 +1,31 @@ |
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/*-------------------------------------------------------------------------
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* |
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* amcheck.h |
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* Shared routines for amcheck verifications. |
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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/amcheck.h |
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* |
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*------------------------------------------------------------------------- |
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*/ |
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#include "storage/bufpage.h" |
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#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 */ |
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typedef void (*IndexCheckableCallback) (Relation index); |
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typedef void (*IndexDoCheckCallback) (Relation rel, |
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Relation heaprel, |
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void *state, |
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bool readonly); |
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extern void amcheck_lock_relation_and_check(Oid indrelid, |
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Oid am_id, |
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IndexDoCheckCallback check, |
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LOCKMODE lockmode, void *state); |
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extern bool index_checkable(Relation rel, Oid am_id); |
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