Horton

Re: Resource Owner reassign Locks

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jeff Janes <jeff.janes@gmail.com>
Cc: Amit Kapila <amit.kapila@huawei.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2012-06-15T22:29:16Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add a small cache of locks owned by a resource owner in ResourceOwner.

Jeff Janes <jeff.janes@gmail.com> writes:
> On Mon, Jun 11, 2012 at 9:30 PM, Amit Kapila <amit.kapila@huawei.com> wrote:
>> MAX_RESOWNER_LOCKS - How did you arrive at number 10 for it. Is there any
>> specific reason for 10.

> I instrumented the code to record the maximum number of locks held by
> a resource owner, and report the max when it was destroyed.  (That
> code is not in this patch).  During a large pg_dump, the vast majority
> of the resource  owners had maximum locks of 2, with some more at 4
> and 6.    Then there was one resource owner, for the top-level
> transaction, at tens or hundreds of thousands (basically one for every
> lockable object).  There was little between 6 and this top-level
> number, so I thought 10 was a good compromise, safely above 6 but not
> so large that searching through the list itself was likely to bog
> down.

> Also, Tom independently suggested the same number.

FYI, I had likewise suggested 10 on the basis of examining pg_dump's
behavior.  It might be a good idea to examine a few other use-cases
before settling on a value.

			regards, tom lane