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Implement mxid_age() to compute multi-xid age

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Report by Josh Berkus
This commit is contained in:
Bruce Momjian
2014-09-10 17:13:04 -04:00
parent 84aa8ba128
commit 36ad1a87a3
5 changed files with 26 additions and 2 deletions
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7
doc/src/sgml/maintenance.sgml
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@ -640,7 +640,12 @@ HINT: Stop the postmaster and vacuum that database in single-user mode.
possible multixact ID still appearing in any tuple of that table.
If this value is older than
<xref linkend="guc-vacuum-multixact-freeze-table-age">, a whole-table
scan is forced. Whole-table <command>VACUUM</> scans, regardless of
scan is forced. <function>mxid_age()</> can be used on
<structname>pg_class</>.<structfield>relminmxid</> to find its age.
</para>
<para>
Whole-table <command>VACUUM</> scans, regardless of
what causes them, enable advancing the value for that table.
Eventually, as all tables in all databases are scanned and their
oldest multixact values are advanced, on-disk storage for older