Re: Speed up transaction completion faster after many relations are accessed in a transaction

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

From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <david.rowley@2ndquadrant.com>
Cc: "Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2019-02-18T23:57:50Z
Lists: pgsql-hackers
David Rowley <david.rowley@2ndquadrant.com> writes:
> On Tue, 19 Feb 2019 at 12:42, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> My own thought about how to improve this situation was just to destroy
>> and recreate LockMethodLocalHash at transaction end (or start)
>> if its size exceeded $some-value.  Leaving it permanently bloated seems
>> like possibly a bad idea, even if we get rid of all the hash_seq_searches
>> on it.

> That seems like a good idea. Although, it would be good to know that
> it didn't add too much overhead dropping and recreating the table when
> every transaction happened to obtain more locks than $some-value.  If
> it did, then maybe we could track the average locks per of recent
> transactions and just ditch the table after the locks are released if
> the locks held by the last transaction exceeded the average *
> 1.something. No need to go near shared memory to do that.

Yeah, I'd deliberately avoided saying how we'd choose $some-value ;-).
Making it adaptive might not be a bad plan.

			regards, tom lane


Commits

  1. Reorder LOCALLOCK structure members to compact the size

  2. Be more careful to not lose sync in the FE/BE protocol.