On 2019/05/10 12:18, David Rowley wrote: > On Fri, 10 May 2019 at 12:08, Bruce Momjian <br...@momjian.us> wrote: >>> 17f206f Set pg_class.relhassubclass for partitioned indexes >> >> I need help with this one. I know the system column existed in previous >> releases, so how is it different now? Do we document system table >> changes that are implementation-behavior in the release notes? Usually >> we don't. > > This appears to be fixing something that likely should have been done > in PG11, where partitioned indexes were added.
That's true. We (Michael and I) felt the need to do this change, because it allowed the pg_partition_tree() code (which is also new in v12) to use the same infrastructure for both partitioned tables and indexes; checking the relhassubclass flag allows to short-circuit scanning pg_inherits to find out that there are no children. > Originally the column > was for inheritance parent tables, then later used for partitioned > tables. It seems partitioned indexes just overlooked setting it to > true in PG11 and this commit fixed that. Of course, backpacking that > fix wouldn't be very useful for partitioned indexes that were already > created, so it was a master only change. There was no discussion on whether or not to back-patch this to v11, but the above makes sense. Regarding whether or not this commit needs a release note mention, I'm not that sure but maybe we should if Justin thinks it's useful information. Thanks, Amit