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Commitfbcbc5d

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Force a checkpoint before committing a CREATE DATABASE command. This
should fix the recent reports of "index is not a btree" failures,as well as preventing a more obscure race condition involving changesto a template database just after copying it with CREATE DATABASE.
1 parent3acca18 commitfbcbc5d

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2 files changed

+44
-2
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2 files changed

+44
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‎doc/src/sgml/backup.sgml

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@@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.68 2005/06/21 20:45:43 tgl Exp $
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$PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.69 2005/06/25 22:47:28 tgl Exp $
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-->
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<chapter id="backup">
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<title>Backup and Restore</title>
@@ -1119,6 +1119,18 @@ restore_command = 'copy /mnt/server/archivedir/%f "%p"' # Windows
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</para>
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</listitem>
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<listitem>
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<para>
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If a <command>CREATE DATABASE</> command is executed while a base
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backup is being taken, and then the template database that the
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<command>CREATE DATABASE</> copied is modified while the base backup
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is still in progress, it is possible that recovery will cause those
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modifications to be propagated into the created database as well.
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This is of course undesirable. To avoid this risk, it is best not to
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modify any template databases while taking a base backup.
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</para>
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</listitem>
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<listitem>
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<para>
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<command>CREATE TABLESPACE</> commands are WAL-logged with the literal

‎src/backend/commands/dbcommands.c

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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.160 2005/06/21 04:02:31 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.161 2005/06/25 22:47:29 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -514,6 +514,36 @@ createdb(const CreatedbStmt *stmt)
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/* Close pg_database, but keep exclusive lock till commit */
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heap_close(pg_database_rel,NoLock);
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/*
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* We force a checkpoint before committing. This effectively means
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* that committed XLOG_DBASE_CREATE operations will never need to be
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* replayed (at least not in ordinary crash recovery; we still have
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* to make the XLOG entry for the benefit of PITR operations).
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* This avoids two nasty scenarios:
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*
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* #1: When PITR is off, we don't XLOG the contents of newly created
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* indexes; therefore the drop-and-recreate-whole-directory behavior
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* of DBASE_CREATE replay would lose such indexes.
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*
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* #2: Since we have to recopy the source database during DBASE_CREATE
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* replay, we run the risk of copying changes in it that were committed
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* after the original CREATE DATABASE command but before the system
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* crash that led to the replay. This is at least unexpected and at
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* worst could lead to inconsistencies, eg duplicate table names.
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*
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* (Both of these were real bugs in releases 8.0 through 8.0.3.)
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*
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* In PITR replay, the first of these isn't an issue, and the second
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* is only a risk if the CREATE DATABASE and subsequent template
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* database change both occur while a base backup is being taken.
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* There doesn't seem to be much we can do about that except document
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* it as a limitation.
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*
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* Perhaps if we ever implement CREATE DATABASE in a less cheesy
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* way, we can avoid this.
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*/
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RequestCheckpoint(true);
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/*
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* Set flag to update flat database file at commit.
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*/

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