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Add code to apply some simple sanity checks to the header fields of a

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page when it's read in, per pghackers discussion around 17-Feb.  Add a
GUC variable zero_damaged_pages that causes the response to be a WARNING
followed by zeroing the page, rather than the normal ERROR; this is per
Hiroshi's suggestion that there needs to be a way to get at the data
in the rest of the table.
This commit is contained in:
Tom Lane
2003-03-28 20:17:13 +00:00
parent bb3c00ee28
commit fd42262836
8 changed files with 104 additions and 73 deletions
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22
doc/src/sgml/runtime.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.174 2003/03/25 16:15:38 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.175 2003/03/28 20:17:13 tgl Exp $
-->
<Chapter Id="runtime">
@ -1599,7 +1599,7 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
<para>
It should be noted that the performance penalty of having
<varname>fsync</> on considerably less in
<varname>fsync</> on is considerably less in
<productname>PostgreSQL</> version 7.1 and later. If you
previously suppressed <function>fsync</> for performance
reasons, you may wish to reconsider your choice.
@ -2174,6 +2174,24 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ZERO_DAMAGED_PAGES</varname> (<type>boolean</type>)</term>
<listitem>
<para>
Detection of a damaged page header normally causes
<productname>PostgreSQL</> to report an error, aborting the current
transaction. Setting <varname>zero_damaged_pages</> to true causes
the system to instead report a warning, zero out the damaged page,
and continue processing. This behavior <emphasis>will lose data</>,
namely all the rows on the damaged page. But it allows you to get
past the error and retrieve rows from any undamaged pages that may
be present in the table. So it is useful for recovering data if
corruption has occurred due to hardware or software error. The
default setting is off, and it can only be changed by a superuser.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>