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Change WAL-logging scheme for multixacts to be more like regular

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transaction IDs, rather than like subtrans; in particular, the information
now survives a database restart.  Per previous discussion, this is
essential for PITR log shipping and for 2PC.
This commit is contained in:
Tom Lane
2005-06-08 15:50:28 +00:00
parent 593badd30b
commit f5b2f60bd1
12 changed files with 560 additions and 274 deletions
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28
doc/src/sgml/ref/pg_resetxlog.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/pg_resetxlog.sgml,v 1.10 2005/04/28 21:47:10 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/pg_resetxlog.sgml,v 1.11 2005/06/08 15:50:21 tgl Exp $
PostgreSQL documentation
-->
@ -23,6 +23,7 @@ PostgreSQL documentation
<arg> -o <replaceable class="parameter">oid</replaceable> </arg>
<arg> -x <replaceable class="parameter">xid</replaceable> </arg>
<arg> -m <replaceable class="parameter">mxid</replaceable> </arg>
<arg> -O <replaceable class="parameter">mxoff</replaceable> </arg>
<arg> -l <replaceable class="parameter">timelineid</replaceable>,<replaceable class="parameter">fileid</replaceable>,<replaceable class="parameter">seg</replaceable> </arg>
<arg choice="plain"><replaceable>datadir</replaceable></arg>
</cmdsynopsis>
@ -32,8 +33,8 @@ PostgreSQL documentation
<title>Description</title>
<para>
<command>pg_resetxlog</command> clears the write-ahead log (WAL) and
optionally resets some other control information (stored in the
<filename>pg_control</> file). This function is sometimes needed
optionally resets some other control information stored in the
<filename>pg_control</> file. This function is sometimes needed
if these files have become corrupted. It should be used only as a
last resort, when the server will not start due to such corruption.
</para>
@ -60,8 +61,9 @@ PostgreSQL documentation
by specifying the <literal>-f</> (force) switch. In this case plausible
values will be substituted for the missing data. Most of the fields can be
expected to match, but manual assistance may be needed for the next OID,
next transaction ID, WAL starting address, and database locale fields.
The first three of these can be set using the switches discussed below.
next transaction ID, next multi-transaction ID and offset,
WAL starting address, and database locale fields.
The first five of these can be set using the switches discussed below.
<command>pg_resetxlog</command>'s own environment is the source for its
guess at the locale fields; take care that <envar>LANG</> and so forth
match the environment that <command>initdb</> was run in.
@ -74,9 +76,10 @@ PostgreSQL documentation
</para>
<para>
The <literal>-o</>, <literal>-x</>, <literal>-m</>, and <literal>-l</>
The <literal>-o</>, <literal>-x</>, <literal>-m</>, <literal>-O</>,
and <literal>-l</>
switches allow the next OID, next transaction ID, next multi-transaction
ID, and WAL starting address values to
ID, next multi-transaction offset, and WAL starting address values to
be set manually. These are only needed when
<command>pg_resetxlog</command> is unable to determine appropriate values
by reading <filename>pg_control</>. Safe values may be determined as
@ -108,6 +111,17 @@ PostgreSQL documentation
</para>
</listitem>
<listitem>
<para>
A safe value for the next multi-transaction offset (<literal>-O</>)
may be determined by looking for the numerically largest
file name in the directory <filename>pg_multixact/members</> under the
data directory, adding one, and then multiplying by 65536. As above,
the file names are in hexadecimal, so the easiest way to do this is to
specify the switch value in hexadecimal and add four zeroes.
</para>
</listitem>
<listitem>
<para>
The WAL starting address (<literal>-l</>) should be