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Add GUC full_page_writes to control writing full pages to WAL.

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This commit is contained in:
Bruce Momjian
2005-07-05 23:18:10 +00:00
parent c19aa704c8
commit 326a7a0788
4 changed files with 55 additions and 5 deletions
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37
doc/src/sgml/runtime.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.335 2005/07/02 19:16:36 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.336 2005/07/05 23:18:09 momjian Exp $
-->
<chapter Id="runtime">
@ -1660,7 +1660,9 @@ SET ENABLE_SEQSCAN TO OFF;
<para>
This option can only be set at server start or in the
<filename>postgresql.conf</filename> file.
<filename>postgresql.conf</filename> file. If this option
is <literal>off</>, consider also turning off
<varname>guc-full-page-writes</>.
</para>
</listitem>
</varlistentry>
@ -1687,6 +1689,37 @@ SET ENABLE_SEQSCAN TO OFF;
</listitem>
</varlistentry>
<varlistentry id="guc-full-page-writes" xreflabel="full_page_writes">
<indexterm>
<primary><varname>full_page_writes</> configuration parameter</primary>
</indexterm>
<term><varname>full_page_writes</varname> (<type>boolean</type>)</term>
<listitem>
<para>
A page write in process during an operating system crash might
be only partially written to disk, leading to an on-disk page
that contains a mix of old and new data. During recovery, the
row changes stored in WAL are not enough to completely restore
the page.
</para>
<para>
When this option is on, the <productname>PostgreSQL</> server
writes full pages to WAL when they first modified after a checkpoint
so full recovery is possible. Turning this option off might lead
to a corrupt system after an operating system crash because
uncorrected partial pages might contain inconsistent or corrupt
data. The risks are less but similar to <varname>fsync</>.
</para>
<para>
This option can only be set at server start or in the
<filename>postgresql.conf</filename> file. The default is
<literal>on</>.
</para>
</listitem>
</varlistentry>
<varlistentry id="guc-wal-buffers" xreflabel="wal_buffers">
<term><varname>wal_buffers</varname> (<type>integer</type>)</term>
<indexterm>