On Mon, 2022-03-28 at 15:05 +0200, Tomas Vondra wrote:
> I've pushed the last version, and backpatched it to 10 (not sure I'd
> call it a bugfix, but I certainly agree with Justin it's worth
> mentioning in the docs, even on older branches).
I'd like to suggest an improvement to this. The current wording could
be read to mean that dead tuples won't get cleaned up in partitioned tables.
By the way, where are the statistics of a partitioned tables used? The actual
tables scanned are always the partitions, and in the execution plans that
I have seen, the optimizer always used the statistics of the partitions.
Yours,
Laurenz Albe
From 5209f228f09e52780535edacfee5f7efd2c25081 Mon Sep 17 00:00:00 2001
From: Laurenz Albe <laurenz.a...@cybertec.at>
Date: Wed, 5 Oct 2022 10:31:47 +0200
Subject: [PATCH] Improve autovacuum doc on partitioned tables
The documentation mentioned that autovacuum doesn't process
partitioned tables, but it was unclear about the impact.
The old wording could be interpreted to mean that there are
problems with dead tuple cleanup on partitioned tables.
Clarify that the only potential problem is autoanalyze, and
that statistics for the partitions will be gathered.
---
doc/src/sgml/maintenance.sgml | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index 759ea5ac9c..53e3fadbaf 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -860,10 +860,15 @@ analyze threshold = analyze base threshold + analyze scale factor * number of tu
</para>
<para>
- Partitioned tables are not processed by autovacuum. Statistics
- should be collected by running a manual <command>ANALYZE</command> when it is
- first populated, and again whenever the distribution of data in its
- partitions changes significantly.
+ Partitioned tables are not processed by autovacuum. This is no problem
+ as far as <command>VACUUM</command> is concerned, since autovacuum will process
+ the partitions. But, as mentioned in <xref linkend="vacuum-for-statistics"/>,
+ it also means that autovacuum won't run <command>ANALYZE</command> on the
+ partitioned table itself. While statistics are gathered for the partitions,
+ some queries may rely on the statistics for the partitioned table. You should
+ collect statistics by running a manual <command>ANALYZE</command> when the
+ partitioned table is first populated, and again whenever the distribution
+ of data in its partitions changes significantly.
</para>
<para>
--
2.37.3
