From: David Rowley <drowley@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Doc: clarify n_distinct_inherited setting
Date: Mon, 13 Oct 2025 20:26:16 +0000
Message-ID: <E1v8P7Y-001XZp-14@gemulon.postgresql.org> (raw)
Doc: clarify n_distinct_inherited setting
There was some confusion around how to adjust the n_distinct estimates
for partitioned tables. Here we try and clarify that
n_distinct_inherited needs to be adjusted rather than n_distinct.
Also fix some slightly misleading text which was talking about table
size rather than table rows, fix a grammatical error, and adjust some
text which indicated that ANALYZE was performing calculations based on
the n_distinct settings. Really it's the query planner that does this
and ANALYZE only stores the overridden n_distinct estimate value in
pg_statistic.
Author: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: David G. Johnston <david.g.johnston@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Backpatch-through: 13
Discussion: https://postgr.es/m/CAApHDvrL7a-ZytM1SP8Uk9nEw9bR2CPzVb+uP+bcNj=_q-ZmVw@mail.gmail.com
Branch
------
REL_17_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/f428b1231ccf39eded9db86acb72c87ad8aa0a8f
Modified Files
--------------
doc/src/sgml/ref/alter_table.sgml | 34 ++++++++++++++++------------------
1 file changed, 16 insertions(+), 18 deletions(-)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-committers@postgresql.org
Cc: drowley@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Doc: clarify n_distinct_inherited setting
In-Reply-To: <E1v8P7Y-001XZp-14@gemulon.postgresql.org>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox