Hi, Alexander: On Fri, 17 May 2024 at 14:05, Alexander Korotkov <aekorot...@gmail.com> wrote:
> On Tue, May 14, 2024 at 5:49 PM Justin Pryzby <pry...@telsasoft.com> > wrote: > > On Thu, May 09, 2024 at 12:51:32AM +0300, Alexander Korotkov wrote: > > > > > However, parent's table extended statistics already covers all its > > > > > children. > > > > > > > > => That's the wrong explanation. It's not that "stats on the parent > > > > table cover its children". It's that there are two types of stats: > > > > stats for the "table hierarchy" and stats for the individual table. > > > > That's true for single-column stats as well as for extended stats. > > > > In both cases, that's indicated by the inh flag in the code and in > the > > > > catalog. > > > > > > > > The right explanation is that extended stats on partitioned tables > are > > > > not similar to indexes. Indexes on parent table are nothing other > than > > > > a mechanism to create indexes on the child tables. That's not true > for > > > > stats. > > > > > > > > See also my prior messages > > > > ZiJW1g2nbQs9ekwK@pryzbyj2023 > > > > Zi5Msg74C61DjJKW@pryzbyj2023 > > > > > > Yes, I understand that parents pg_statistic entry with stainherit == > > > true includes statistics for the children. I tried to express this by > > > word "covers". But you're right, this is the wrong explanation. > > > > > > Can I, please, ask you to revise the patch? > > > > I tried to make this clear but it'd be nice if someone (Tomas/Alvaro?) > > would check that this says what's wanted. > > Thank you! > > I've assembled the patches with the pending fixes. > 0001 – The patch by Dmitry Koval for fixing detection of name > collision in SPLIT partition operation. Also, I found that name > collision detection doesn't work well for MERGE partitions. I've > added fix for that to this patch as well. > 0002 -– Patch for skipping copy of extended statistics. I would > appreciate more feedback about wording, but I'd like to get a correct > behavior into the source tree sooner. If the docs and/or comments > need further improvements, we can fix that later. > > I'm going to push both if no objections. > Thank you for working on this patch set! Some minor things: 0001: partition_split.sql 157 +-- Check that detection, that the new partition has the same name as one of 158 +-- the merged partitions, works correctly for temporary partitions Test for split with comment for merge. Maybe better something like: "Split partition of a temporary table when one of the partitions after split has the same name as the partition being split" 0002: analgous -> analogous (maybe better using "like" instead of "analogous to") heirarchy -> hierarchy alter_table.sgml: Maybe in documentation it's better not to provide reasoning, just state how it works: for consistency with <command>CREATE TABLE PARTITION OF</command> -> similar to <command>CREATE TABLE PARTITION OF</command> Regards, Pavel Borisov
