On Wed, Sep 6, 2023 at 05:53:56AM +0200, Laurenz Albe wrote:
> > We may have different mental models here. This relates to the part
> > that I wasn't keen on in your patch, i.e:
> >
> > + The partitions of a partitioned table are normal tables and get
> > processed
> > + by autovacuum
> >
> > While I agree that the majority of partitions are likely to be
> > relkind='r', which you might ordinarily consider a "normal table", you
> > just might change your mind when you try to INSERT or UPDATE records
> > that would violate the partition constraint. Some partitions might
> > also be themselves partitioned tables and others might be foreign
> > tables. That does not really matter much when it comes to what
> > autovacuum does or does not do, but I'm not really keen to imply in
> > our documents that partitions are "normal tables".
>
> Agreed, there are differences between partitions and normal tables.
> And this is not the place in the documentation where we would like to
> get into detail about the differences.
>
> Attached is the next version of my patch.
I adjusted your patch to be shorter and clearer, patch attached. I am
planning to apply this back to PG 11.
--
Bruce Momjian <[email protected]> https://momjian.us
EDB https://enterprisedb.com
Only you can decide what is important to you.
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index 9cf9d030a8..70b5576037 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -861,10 +861,16 @@ 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 do not directly store tuples and consequently do not
+ require autovacuum to perform automated <command>VACUUM</command>.
+ (Autovacuum does perform <command>VACUUM</command> on table
+ partitions just like other tables.) Unfortunately, this also means
+ that autovacuum doesn't run <command>ANALYZE</command> on partitioned
+ tables, and this can cause suboptimal plans for queries that reference
+ partitioned table statistics. You can work around this problem by
+ manually running <command>ANALYZE</command> on partitioned tables
+ when they are first populated, and again whenever the distribution
+ of data in their partitions changes significantly.
</para>
<para>
