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Reword doc blurb for vacuumdb --analyze-in-stages

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Make users aware that using it in a database with existing stats might
cause transient problems.

Author: Nikolai Berkoff <nikolai.berkoff@pm.me>
Discussion: https://postgr.es/m/s-kSljtWXMWgMfGTztPTPcS80R8FHdOrBxDTnrQI6GMZbT7au1A4b0fzaSFtKwCI8nwN0MhgPLfVOTvJ7DwTjkip4P3d0o4VgrMJs4OLN-o=@pm.me
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Alvaro Herrera 2021-11-05 11:22:30 -03:00
parent bef47ff85d
commit 00a354a135
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16
doc/src/sgml/ref/vacuumdb.sgml
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@ -398,15 +398,19 @@ PostgreSQL documentation
<para>
Only calculate statistics for use by the optimizer (no vacuum),
like <option>--analyze-only</option>. Run several (currently three)
stages of analyze with different configuration settings, to produce
usable statistics faster.
stages of analyze; the first stage uses the lowest possible statistics
target (see <xref linkend="guc-default-statistics-target"/>)
to produce usable statistics faster, and subsequent stages build the
full statistics.
</para>
<para>
This option is useful to analyze a database that was newly populated
from a restored dump or by <command>pg_upgrade</command>. This option
will try to create some statistics as fast as possible, to make the
database usable, and then produce full statistics in the subsequent
This option is only useful to analyze a database that current has
no statistics or wholly incorrect ones, such as if it is newly
populated from a restored dump or by <command>pg_upgrade</command>.
Be aware that running this option in a database with existing
statistics may cause the query optimizer choices to become
transiently worse due to the low statistics targets of the early
stages.
</para>
</listitem>