From: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
---|---|
To: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us> |
Cc: | Justin Pryzby <pryzby(at)telsasoft(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: pg12 release notes |
Date: | 2019-05-10 03:45:54 |
Message-ID: | 17a07ed6-4d17-838e-2a8f-fd125c22e03e@lab.ntt.co.jp |
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Lists: | pgsql-hackers |
On 2019/05/10 12:18, David Rowley wrote:
> On Fri, 10 May 2019 at 12:08, Bruce Momjian <bruce(at)momjian(dot)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
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