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Transaction IDs wrap around, per my proposal of 13-Aug-01. More
documentation to come, but the code is all here. initdb forced.
This commit is contained in:
Tom Lane
@ -1,6 +1,6 @@
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<!--
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Documentation of the system catalogs, directed toward PostgreSQL developers
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$Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.21 2001/08/21 16:35:58 tgl Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.22 2001/08/26 16:55:58 tgl Exp $
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-->
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<chapter id="catalogs">
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@ -840,11 +840,34 @@
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<entry><type>oid</type></entry>
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<entry></entry>
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<entry>
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Last oid in existence after the database was created; useful
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Last system OID in the database; useful
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particularly to <application>pg_dump</application>
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</entry>
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</row>
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<row>
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<entry>datvacuumxid</entry>
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<entry><type>xid</type></entry>
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<entry></entry>
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<entry>
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All tuples inserted or deleted by transaction IDs before this one
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have been marked as known committed or known aborted in this database.
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This is used to determine when commit-log space can be recycled.
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</entry>
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</row>
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<row>
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<entry>datfrozenxid</entry>
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<entry><type>xid</type></entry>
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<entry></entry>
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<entry>
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All tuples inserted by transaction IDs before this one have been
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relabeled with a permanent (<quote>frozen</>) transaction ID in this
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database. This is useful to check whether a database must be vacuumed
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soon to avoid transaction ID wraparound problems.
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</entry>
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</row>
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<row>
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<entry>datpath</entry>
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<entry><type>text</type></entry>
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@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_database.sgml,v 1.17 2000/11/15 19:43:39 petere Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_database.sgml,v 1.18 2001/08/26 16:55:59 tgl Exp $
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Postgres documentation
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-->
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@ -284,6 +284,20 @@ comment from Olly; response from Thomas...
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simply by setting the flag false). The <literal>template0</literal>
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database is normally marked this way to prevent modification of it.
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</para>
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<para>
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After preparing a template database, or making any changes to one,
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it is a good idea to perform
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<command>VACUUM FREEZE</> or <command>VACUUM FULL FREEZE</> in that
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database. If this is done when there are no other open transactions
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in the same database, then it is guaranteed that all tuples in the
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database are <quote>frozen</> and will not be subject to transaction
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ID wraparound problems. This is particularly important for a database
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that will have <literal>datallowconn</literal> set to false, since it
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will be impossible to do routine maintenance <command>VACUUM</>s on
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such a database.
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See the Administrator's Guide for more information.
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</para>
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</refsect2>
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</refsect1>
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@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/vacuum.sgml,v 1.17 2001/07/10 22:09:28 tgl Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/vacuum.sgml,v 1.18 2001/08/26 16:55:59 tgl Exp $
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Postgres documentation
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-->
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@ -20,11 +20,11 @@ Postgres documentation
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</refnamediv>
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<refsynopsisdiv>
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<refsynopsisdivinfo>
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<date>2001-07-10</date>
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<date>2001-08-26</date>
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</refsynopsisdivinfo>
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<synopsis>
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VACUUM [ FULL ] [ VERBOSE ] [ <replaceable class="PARAMETER">table</replaceable> ]
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VACUUM [ FULL ] [ VERBOSE ] ANALYZE [ <replaceable class="PARAMETER">table</replaceable> [ (<replaceable class="PARAMETER">column</replaceable> [, ...] ) ] ]
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VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ <replaceable class="PARAMETER">table</replaceable> ]
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VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] ANALYZE [ <replaceable class="PARAMETER">table</replaceable> [ (<replaceable class="PARAMETER">column</replaceable> [, ...] ) ] ]
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</synopsis>
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<refsect2 id="R2-SQL-VACUUM-1">
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@ -46,6 +46,14 @@ VACUUM [ FULL ] [ VERBOSE ] ANALYZE [ <replaceable class="PARAMETER">table</repl
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>FREEZE</term>
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<listitem>
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<para>
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Selects aggressive <quote>freezing</quote> of tuples.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>VERBOSE</term>
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<listitem>
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@ -168,16 +176,6 @@ NOTICE: Index <replaceable class="PARAMETER">index</replaceable>: Pages 28;
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only that table.
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</para>
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<para>
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Plain <command>VACUUM</command> simply reclaims space and makes it
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available for re-use. This form of the command can operate in parallel
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with normal reading and writing of the table. <command>VACUUM
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FULL</command> does more extensive processing, including moving of tuples
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across blocks to try to compact the table to the minimum number of disk
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blocks. This is much slower and requires an exclusive lock on each table
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while it is being processed.
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</para>
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<para>
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<command>VACUUM ANALYZE</command> performs a <command>VACUUM</command>
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and then an <command>ANALYZE</command> for each selected table. This
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@ -186,6 +184,33 @@ NOTICE: Index <replaceable class="PARAMETER">index</replaceable>: Pages 28;
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for more details about its processing.
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</para>
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<para>
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Plain <command>VACUUM</command> (without <literal>FULL</>) simply reclaims
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space and makes it
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available for re-use. This form of the command can operate in parallel
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with normal reading and writing of the table. <command>VACUUM
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FULL</command> does more extensive processing, including moving of tuples
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across blocks to try to compact the table to the minimum number of disk
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blocks. This form is much slower and requires an exclusive lock on each
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table while it is being processed.
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</para>
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<para>
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<command>FREEZE</command> is a special-purpose option that
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causes tuples to be marked <quote>frozen</quote> as soon as possible,
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rather than waiting until they are quite old. If this is done when there
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are no other open transactions in the same database, then it is guaranteed
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that all tuples in the database are <quote>frozen</> and will not be
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subject to transaction ID wraparound problems, no matter how long the
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database is left un-vacuumed.
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<command>FREEZE</command> is not recommended for routine use. Its only
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intended usage is in connection with preparation of user-defined template
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databases, or other databases that are completely read-only and will not
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receive routine maintenance <command>VACUUM</> operations.
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See <xref linkend="sql-createdatabase" endterm="sql-createdatabase-title">
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for details.
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</para>
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<refsect2 id="R2-SQL-VACUUM-3">
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<refsect2info>
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<date>2001-07-10</date>
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