Horton

Re: hyrax vs. RelationBuildPartitionDesc

Amit Langote <langote_amit_f8@lab.ntt.co.jp>

View thread View on postgr.es
From: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
To: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2019-03-14T01:40:31Z
Lists: pgsql-hackers

Attachments

On 2019/03/14 5:18, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> On Wed, Mar 13, 2019 at 3:14 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> 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.
> 
>> To your question, I think it probably can't share a context.  Briefly,
>> rd_partkey can't change ever, except that when a partitioned relation
>> is in the process of being created it is briefly NULL; once it obtains
>> a value, that value cannot be changed.  If you want to range-partition
>> a list-partitioned table or something like that, you have to drop the
>> table and create a new one.  I think that's a perfectly acceptable
>> permanent limitation and I have no urge whatever to change it.
>> rd_partdesc changes when you attach or detach a child partition.
>> rd_partcheck is the reverse: it changes when you attach or detach this
>> partition to or from a parent.
> 
> Got it.  Yeah, it seems like the clearest and least bug-prone solution
> is for those to be in three separate sub-contexts.  The only reason
> I was trying to avoid that was the angle of how to back-patch into 11.
> However, we can just add the additional context pointer field at the
> end of the Relation struct in v11, and that should be good enough to
> avoid ABI problems.

Agree that rd_partcheck needs its own context as you have complained in
the past [1].

I think we'll need to back-patch this fix to PG 10 as well.  I've attached
patches for all 3 branches.

Thanks,
Amit

[1] https://www.postgresql.org/message-id/22236.1523374067%40sss.pgh.pa.us

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.