Horton

Re: hyrax vs. RelationBuildPartitionDesc

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2019-03-13T19:14:52Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> On Wed, Mar 13, 2019 at 2:26 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I think that RelationBuildPartitionDesc could use some additional cleanup
>> or at least better commenting.  In particular, it's neither documented nor
>> obvious to the naked eye why rel->rd_partdesc mustn't get set till the
>> very end.  As the complainant, I'm willing to go fix that, but do you want
>> to push your patch first so it doesn't get broken?  Or I could include
>> your patch in the cleanup.

> It seems kinda obvious to me why rel->rd_partdesc can't get set until
> the end.  Isn't it just that you'd better not set a permanent pointer
> to a data structure until you're past any code that might ERROR, which
> is pretty much everything?  That principle applies to lots of
> PostgreSQL code, not just this.

Yeah, but usually there's some comment pointing it out.  I also wonder
if there aren't corner-case bugs; it seems a bit bogus for example that
rd_pdcxt is created without any thought as to whether it might be set
already.  It's not clear whether this has been written with the
level of paranoia that's appropriate for messing with a relcache entry,
and some comments would make it a lot clearer (a) if that is true and
(b) what assumptions are implicitly being shared with relcache.c.

Meanwhile, who's going to take point on cleaning up rd_partcheck?
I don't really understand this code well enough to know whether that
can share one of the existing partitioning-related sub-contexts.

			regards, tom lane

Commits

  1. Load relcache entries' partitioning data on-demand, not immediately.

  2. Prevent memory leaks associated with relcache rd_partcheck structures.

  3. Don't copy PartitionBoundInfo in set_relation_partition_info.

  4. Further reduce memory footprint of CLOBBER_CACHE_ALWAYS testing.

  5. Fix some oversights in commit 2455ab488.

  6. Defend against leaks into RelationBuildPartitionDesc.

  7. Allow ATTACH PARTITION with only ShareUpdateExclusiveLock.