On Wed, Jan 18, 2023 at 10:15:18AM +0100, Laurenz Albe wrote: > On Tue, 2023-01-17 at 16:16 -0500, Bruce Momjian wrote: > > On Tue, Jan 17, 2023 at 03:00:50PM -0600, Justin Pryzby wrote: > > > Maybe (all?) the clarification the docs need is to say: > > > "Partitioned tables are not *themselves* processed by autovacuum." > > > > Yes, I think the lack of autovacuum needs to be specifically mentioned > > since most people assume autovacuum handles _all_ statistics updating.
That's what 61fa6ca79 aimed to do. Laurenz is suggesting further clarification. > > Can someone summarize how bad it is we have no statistics on partitioned > > tables? It sounds bad to me. > > Andrey Lepikhov had an example earlier in this thread[1]. It doesn't take > an exotic query. > > Attached is a new version of my patch that tries to improve the wording. I tweaked this a bit to end up with: > - Partitioned tables are not processed by autovacuum. Statistics > - should be collected by running a manual <command>ANALYZE</command> when > it is > + The leaf partitions of a partitioned table are normal tables and are > processed > + by autovacuum; however, autovacuum does not process the partitioned > table itself. > + This is no problem as far as <command>VACUUM</command> is concerned, > since > + there's no need to vacuum the empty, partitioned table. But, as > mentioned in > + <xref linkend="vacuum-for-statistics"/>, it also means that autovacuum > won't > + run <command>ANALYZE</command> on the partitioned table. > + Although statistics are automatically gathered on its leaf partitions, > some queries also need > + statistics on the partitioned table to run optimally. 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> "partitions are normal tables" was techically wrong, as partitions can also be partitioned. -- Justin