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Transaction IDs wrap around, per my proposal of 13-Aug-01. More

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documentation to come, but the code is all here.  initdb forced.
This commit is contained in:
Tom Lane
2001-08-26 16:56:03 +00:00
parent d1ee78f296
commit bc7d37a525
29 changed files with 617 additions and 171 deletions
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16
doc/src/sgml/ref/create_database.sgml
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@@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_database.sgml,v 1.17 2000/11/15 19:43:39 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_database.sgml,v 1.18 2001/08/26 16:55:59 tgl Exp $
Postgres documentation
-->
@@ -284,6 +284,20 @@ comment from Olly; response from Thomas...
simply by setting the flag false). The <literal>template0</literal>
database is normally marked this way to prevent modification of it.
</para>
<para>
After preparing a template database, or making any changes to one,
it is a good idea to perform
<command>VACUUM FREEZE</> or <command>VACUUM FULL FREEZE</> in that
database. If this is done when there are no other open transactions
in the same database, then it is guaranteed that all tuples in the
database are <quote>frozen</> and will not be subject to transaction
ID wraparound problems. This is particularly important for a database
that will have <literal>datallowconn</literal> set to false, since it
will be impossible to do routine maintenance <command>VACUUM</>s on
such a database.
See the Administrator's Guide for more information.
</para>
</refsect2>
</refsect1>

53
doc/src/sgml/ref/vacuum.sgml
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@@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/vacuum.sgml,v 1.17 2001/07/10 22:09:28 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/vacuum.sgml,v 1.18 2001/08/26 16:55:59 tgl Exp $
Postgres documentation
-->
@@ -20,11 +20,11 @@ Postgres documentation
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>2001-07-10</date>
<date>2001-08-26</date>
</refsynopsisdivinfo>
<synopsis>
VACUUM [ FULL ] [ VERBOSE ] [ <replaceable class="PARAMETER">table</replaceable> ]
VACUUM [ FULL ] [ VERBOSE ] ANALYZE [ <replaceable class="PARAMETER">table</replaceable> [ (<replaceable class="PARAMETER">column</replaceable> [, ...] ) ] ]
VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ <replaceable class="PARAMETER">table</replaceable> ]
VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] ANALYZE [ <replaceable class="PARAMETER">table</replaceable> [ (<replaceable class="PARAMETER">column</replaceable> [, ...] ) ] ]
</synopsis>
<refsect2 id="R2-SQL-VACUUM-1">
@@ -46,6 +46,14 @@ VACUUM [ FULL ] [ VERBOSE ] ANALYZE [ <replaceable class="PARAMETER">table</repl
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>FREEZE</term>
<listitem>
<para>
Selects aggressive <quote>freezing</quote> of tuples.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>VERBOSE</term>
<listitem>
@@ -168,16 +176,6 @@ NOTICE: Index <replaceable class="PARAMETER">index</replaceable>: Pages 28;
only that table.
</para>
<para>
Plain <command>VACUUM</command> simply reclaims space and makes it
available for re-use. This form of the command can operate in parallel
with normal reading and writing of the table. <command>VACUUM
FULL</command> does more extensive processing, including moving of tuples
across blocks to try to compact the table to the minimum number of disk
blocks. This is much slower and requires an exclusive lock on each table
while it is being processed.
</para>
<para>
<command>VACUUM ANALYZE</command> performs a <command>VACUUM</command>
and then an <command>ANALYZE</command> for each selected table. This
@@ -186,6 +184,33 @@ NOTICE: Index <replaceable class="PARAMETER">index</replaceable>: Pages 28;
for more details about its processing.
</para>
<para>
Plain <command>VACUUM</command> (without <literal>FULL</>) simply reclaims
space and makes it
available for re-use. This form of the command can operate in parallel
with normal reading and writing of the table. <command>VACUUM
FULL</command> does more extensive processing, including moving of tuples
across blocks to try to compact the table to the minimum number of disk
blocks. This form is much slower and requires an exclusive lock on each
table while it is being processed.
</para>
<para>
<command>FREEZE</command> is a special-purpose option that
causes tuples to be marked <quote>frozen</quote> as soon as possible,
rather than waiting until they are quite old. If this is done when there
are no other open transactions in the same database, then it is guaranteed
that all tuples in the database are <quote>frozen</> and will not be
subject to transaction ID wraparound problems, no matter how long the
database is left un-vacuumed.
<command>FREEZE</command> is not recommended for routine use. Its only
intended usage is in connection with preparation of user-defined template
databases, or other databases that are completely read-only and will not
receive routine maintenance <command>VACUUM</> operations.
See <xref linkend="sql-createdatabase" endterm="sql-createdatabase-title">
for details.
</para>
<refsect2 id="R2-SQL-VACUUM-3">
<refsect2info>
<date>2001-07-10</date>