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Further adjust guidance for running vacuumdb after pg_upgrade.

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Since pg_upgrade does not transfer the cumulative statistics used
to trigger autovacuum and autoanalyze, the server may take much
longer than expected to process them post-upgrade.  Currently, we
recommend analyzing only relations for which optimizer statistics
were not transferred by using the --analyze-in-stages and
--missing-stats-only options.  This commit appends another
recommendation to analyze all relations to update the relevant
cumulative statistics by using the --analyze-only option.  This is
similar to the recommendation for pg_stat_reset().

Reported-by: Christoph Berg <myon@debian.org>
Reviewed-by: Christoph Berg <myon@debian.org>
Discussion: https://postgr.es/m/aAfxfKC82B9NvJDj%40msg.df7cb.de
This commit is contained in:
Nathan Bossart
2025-04-30 14:12:59 -05:00
parent f60420cff6
commit d5f1b6a75b
2 changed files with 13 additions and 8 deletions
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12
doc/src/sgml/ref/pgupgrade.sgml
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@ -833,17 +833,19 @@ psql --username=postgres --file=script.sql postgres
<para>
Because not all statistics are not transferred by
<command>pg_upgrade</command>, you will be instructed to run a command to
<command>pg_upgrade</command>, you will be instructed to run commands to
regenerate that information at the end of the upgrade. You might need to
set connection parameters to match your new cluster.
</para>
<para>
Using <command>vacuumdb --all --analyze-only --missing-stats-only</command>
can efficiently generate such statistics. Alternatively,
First, use
<command>vacuumdb --all --analyze-in-stages --missing-stats-only</command>
can be used to generate minimal statistics quickly. For either command,
the use of <option>--jobs</option> can speed it up.
to quickly generate minimal optimizer statistics for relations without
any. Then, use <command>vacuumdb --all --analyze-only</command> to ensure
all relations have updated cumulative statistics for triggering vacuum and
analyze. For both commands, the use of <option>--jobs</option> can speed
it up.
If <varname>vacuum_cost_delay</varname> is set to a non-zero
value, this can be overridden to speed up statistics generation
using <envar>PGOPTIONS</envar>, e.g., <literal>PGOPTIONS='-c