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Repair some REINDEX problems per recent discussions. The relcache is
now able to cope with assigning new relfilenode values to nailed-in-cache indexes, so they can be reindexed using the fully crash-safe method. This leaves only shared system indexes as special cases. Remove the 'index deactivation' code, since it provides no useful protection in the shared- index case. Require reindexing of shared indexes to be done in standalone mode, but remove other restrictions on REINDEX. -P (IgnoreSystemIndexes) now prevents using indexes for lookups, but does not disable index updates. It is therefore safe to allow from PGOPTIONS. Upshot: reindexing system catalogs can be done without a standalone backend for all cases except shared catalogs.
This commit is contained in:
Tom Lane
@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/postgres-ref.sgml,v 1.36 2003/09/18 20:30:15 tgl Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/postgres-ref.sgml,v 1.37 2003/09/24 18:54:01 tgl Exp $
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PostgreSQL documentation
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-->
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@ -177,9 +177,9 @@ PostgreSQL documentation
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<term><option>-P</option></term>
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<listitem>
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<para>
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Ignore system indexes while scanning/updating system tables. The
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<command>REINDEX</command> command for system tables/indexes
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requires this option to be used.
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Ignore system indexes when reading system tables (but still update
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the indexes when modifying the tables). This is useful when
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recovering from damaged system indexes.
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</para>
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</listitem>
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</varlistentry>
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@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/reindex.sgml,v 1.20 2003/09/11 21:42:20 momjian Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/reindex.sgml,v 1.21 2003/09/24 18:54:01 tgl Exp $
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PostgreSQL documentation
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-->
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@ -56,43 +56,6 @@ REINDEX { DATABASE | TABLE | INDEX } <replaceable class="PARAMETER">name</replac
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</listitem>
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</itemizedlist>
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</para>
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<para>
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If you suspect corruption of an index on a user table, you can
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simply rebuild that index, or all indexes on the table, using
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<command>REINDEX INDEX</command> or <command>REINDEX
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TABLE</command>. Another approach to dealing with a corrupted
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user-table index is just to drop and recreate it. This may in fact
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be preferable if you would like to maintain some semblance of
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normal operation on the table meanwhile. <command>REINDEX</>
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acquires exclusive lock on the table, while <command>CREATE
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INDEX</> only locks out writes not reads of the table.
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</para>
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<para>
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Things are more difficult if you need to recover from corruption of
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an index on a system table. In this case it's important for the
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system to not have used any of the suspect indexes itself.
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(Indeed, in this sort of scenario you may find that server
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processes are crashing immediately at start-up, due to reliance on
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the corrupted indexes.) To recover safely, the server must be shut
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down and a stand-alone <productname>PostgreSQL</productname> server
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must be started instead with the command-line options
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<option>-O</option> and <option>-P</option>. (These options allow
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system table modifications and prevent use of system indexes,
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respectively.) Then, <command>REINDEX DATABASE</>,
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<command>REINDEX TABLE</>, or <command>REINDEX INDEX</> can be
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issued, depending on how much you want to reconstruct. If in
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doubt, use <command>REINDEX DATABASE FORCE</> to force
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reconstruction of all system indexes in the database. Then quit
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the standalone server session and restart the real server.
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</para>
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<para>
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See the <xref linkend="app-postgres"> reference page for more
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information about how to interact with the stand-alone server
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interface.
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</para>
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</refsect1>
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<refsect1>
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@ -104,8 +67,8 @@ REINDEX { DATABASE | TABLE | INDEX } <replaceable class="PARAMETER">name</replac
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<listitem>
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<para>
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Recreate all system indexes of a specified database. Indexes on
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user tables are not included. This form of <command>REINDEX</>
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can only be used in stand-alone mode (see above).
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user tables are not processed. Also, indexes on shared system
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catalogs are skipped except in stand-alone mode (see below).
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</para>
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</listitem>
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</varlistentry>
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@ -114,7 +77,8 @@ REINDEX { DATABASE | TABLE | INDEX } <replaceable class="PARAMETER">name</replac
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<term><literal>TABLE</literal></term>
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<listitem>
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<para>
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Recreate all indexes of a specified table.
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Recreate all indexes of a specified table. If the table has a
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secondary <quote>TOAST</> table, that is reindexed as well.
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</para>
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</listitem>
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</varlistentry>
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@ -142,16 +106,93 @@ REINDEX { DATABASE | TABLE | INDEX } <replaceable class="PARAMETER">name</replac
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<term><literal>FORCE</literal></term>
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<listitem>
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<para>
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Force rebuild of system indexes. Without this key word,
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<command>REINDEX</> skips system indexes that are not marked
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invalid. <literal>FORCE</> is irrelevant for <command>REINDEX
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INDEX</> or when reindexing user indexes.
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This is an obsolete option; it is ignored if specified.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>
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If you suspect corruption of an index on a user table, you can
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simply rebuild that index, or all indexes on the table, using
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<command>REINDEX INDEX</command> or <command>REINDEX
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TABLE</command>. Another approach to dealing with a corrupted
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user-table index is just to drop and recreate it. This may in fact
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be preferable if you would like to maintain some semblance of
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normal operation on the table meanwhile. <command>REINDEX</>
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acquires exclusive lock on the table, while <command>CREATE
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INDEX</> only locks out writes not reads of the table.
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</para>
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<para>
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Things are more difficult if you need to recover from corruption of
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an index on a system table. In this case it's important for the
|
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system to not have used any of the suspect indexes itself.
|
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(Indeed, in this sort of scenario you may find that server
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processes are crashing immediately at start-up, due to reliance on
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the corrupted indexes.) To recover safely, the server must be started
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with the <option>-P</option> option, which prevents it from using
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indexes for system catalog lookups.
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</para>
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<para>
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One way to do this is to shut down the postmaster and start a stand-alone
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<productname>PostgreSQL</productname> server
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with the <option>-P</option> option included on its command line.
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Then, <command>REINDEX DATABASE</>,
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<command>REINDEX TABLE</>, or <command>REINDEX INDEX</> can be
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issued, depending on how much you want to reconstruct. If in
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doubt, use <command>REINDEX DATABASE</> to select
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reconstruction of all system indexes in the database. Then quit
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the standalone server session and restart the regular server.
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See the <xref linkend="app-postgres"> reference page for more
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information about how to interact with the stand-alone server
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interface.
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</para>
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<para>
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Alternatively, a regular server session can be started with
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<option>-P</option> included in its command line options.
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The method for doing this varies across clients, but in all
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<application>libpq</>-based clients, it is possible to set
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the <envar>PGOPTIONS</envar> environment variable to <literal>-P</>
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before starting the client. Note that while this method does not
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require locking out other clients, it may still be wise to prevent
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other users from connecting to the damaged database until repairs
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have been completed.
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</para>
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<para>
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If corruption is suspected in the indexes of any of the shared
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system catalogs (<structname>pg_database</structname>,
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<structname>pg_group</structname>, or
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<structname>pg_shadow</structname>), then a standalone server
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must be used to repair it. <command>REINDEX</> will not process
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shared catalogs in multiuser mode.
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</para>
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<para>
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For all indexes except the shared system catalogs, <command>REINDEX</>
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is crash-safe and transaction-safe. <command>REINDEX</> is not
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crash-safe for shared indexes, which is why this case is disallowed
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during normal operation. If a failure occurs while reindexing one
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of these catalogs in standalone mode, it is important that the failure
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be rectified and the <command>REINDEX</> operation redone
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before attempting to restart the regular server.
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</para>
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<para>
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Prior to <productname>PostgreSQL</productname> 7.4, <command>REINDEX
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TABLE</> did not automatically process TOAST tables, and so those had
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to be reindexed by separate commands. This is still possible, but
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redundant.
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</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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@ -172,11 +213,15 @@ REINDEX INDEX my_index;
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</para>
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<para>
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Rebuild all system indexes (this will only work in a stand-alone
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server session):
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Rebuild all system indexes in a particular database, without trusting them
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to be valid already:
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<programlisting>
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REINDEX DATABASE my_database FORCE;
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$ <userinput>export PGOPTIONS="-P"</userinput>
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$ <userinput>psql broken_db</userinput>
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...
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broken_db=> REINDEX DATABASE broken_db;
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broken_db=> \q
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</programlisting>
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</para>
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</refsect1>
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