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Commitf36d137

Browse files
michaelpqpull[bot]
authored andcommitted
Fix corruption of templates after CREATE DATABASE .. STRATEGY WAL_LOG
WAL_LOG does a scan of the template's pg_class to determine the set ofrelations that need to be copied from a template database to the newone. However, as coded in9c08aea, this copy strategy would load thepages of pg_class without considering it as a permanent relation,causing the loaded pages to never be flushed when they should. Anymodification of the template's pg_class, mostly through DDLs, would thenbe missed, causing corruptions.STRATEGY = WAL_LOG is the default over FILE_COPY since it has beenintroduced, so any changes done to pg_class on a database template wouldbe gone. Updates of database templates should be a rare thing, so theimpact of this bug should be hopefully limited. The pre-14 defaultstrategy FILE_COPY is safe, and can be used as a workaround.Ryo Matsumura has found and analyzed the issue, and Nathan has written atest able to reproduce the failure (with few tweaks from me).Backpatch down to 15, where STRATEGY = WAL_LOG has been introduced.Author: Nathan Bossart, Ryo MatsumuraReviewed-by: Dilip Kumar, Michael PaquierDiscussion:https://postgr.es/m/TYCPR01MB6868677E499C9AD5123084B5E8A39@TYCPR01MB6868.jpnprd01.prod.outlook.comBackpatch-through: 15
1 parent47c670b commitf36d137

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3 files changed

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-1
lines changed

3 files changed

+47
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‎src/backend/commands/dbcommands.c

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@@ -296,7 +296,7 @@ ScanSourceDatabasePgClass(Oid tbid, Oid dbid, char *srcpath)
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CHECK_FOR_INTERRUPTS();
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buf=ReadBufferWithoutRelcache(rlocator,MAIN_FORKNUM,blkno,
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RBM_NORMAL,bstrategy,false);
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RBM_NORMAL,bstrategy,true);
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LockBuffer(buf,BUFFER_LOCK_SHARE);
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page=BufferGetPage(buf);

‎src/test/recovery/meson.build

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@@ -39,6 +39,7 @@ tests += {
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't/031_recovery_conflict.pl',
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't/032_relfilenode_reuse.pl',
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't/033_replay_tsp_drops.pl',
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't/034_create_database.pl',
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],
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},
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}
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# Copyright (c) 2023, PostgreSQL Global Development Group
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# Test WAL replay for CREATE DATABASE .. STRATEGY WAL_LOG.
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use strict;
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use warnings;
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use PostgreSQL::Test::Cluster;
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use PostgreSQL::Test::Utils;
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use Test::More;
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my$node = PostgreSQL::Test::Cluster->new('node');
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$node->init;
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$node->start;
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# This checks that any DDLs run on the template database that modify pg_class
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# are persisted after creating a database from it using the WAL_LOG strategy,
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# as a direct copy of the template database's pg_class is used in this case.
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my$db_template ="template1";
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my$db_new ="test_db_1";
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# Create table. It should persist on the template database.
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$node->safe_psql("postgres",
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"CREATE DATABASE$db_new STRATEGY WAL_LOG TEMPLATE$db_template;");
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$node->safe_psql($db_template,"CREATE TABLE tab_db_after_create_1 (a INT);");
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# Flush the changes affecting the template database, then replay them.
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$node->safe_psql("postgres","CHECKPOINT;");
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$node->stop('immediate');
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$node->start;
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my$result =$node->safe_psql($db_template,
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"SELECT count(*) FROM pg_class WHERE relname LIKE 'tab_db_%';");
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is($result,"1",
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"check that table exists on template after crash, with checkpoint");
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# The new database should have no tables.
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$result =$node->safe_psql($db_new,
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"SELECT count(*) FROM pg_class WHERE relname LIKE 'tab_db_%';");
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is($result,"0",
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"check that there are no tables from template on new database after crash"
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);
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done_testing();

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