Horton

Re: [HACKERS] Moving relation extension locks out of heavyweight lock manager

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Mahendra Singh Thalor <mahi6run@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>, Masahiko Sawada <masahiko.sawada@2ndquadrant.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Michael Paquier <michael@paquier.xyz>, Mithun Cy <mithun.cy@enterprisedb.com>, Thomas Munro <thomas.munro@enterprisedb.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2020-03-06T04:45:03Z
Lists: pgsql-hackers

Commits

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  1. Allow page lock to conflict among parallel group members.

  2. Allow relation extension lock to conflict among parallel group members.

  3. Add assert to ensure that page locks don't participate in deadlock cycle.

  4. Assert that we don't acquire a heavyweight lock on another object after

  5. Fix unsafe usage of strerror(errno) within ereport().

On Fri, Mar 6, 2020 at 2:19 AM Robert Haas <robertmhaas@gmail.com> wrote:
>
> On Thu, Mar 5, 2020 at 2:18 PM Mahendra Singh Thalor <mahi6run@gmail.com> wrote:
> > Here, attaching new patch set for review.
>
> I was kind of assuming that the way this would work is that it would
> set a flag or increment a counter or something when we acquire a
> relation extension lock, and then reverse the process when we release
> it. Then the Assert could just check the flag. Walking the whole
> LOCALLOCK table is expensive.
>

I think we can keep such a flag in TopTransactionState.   We free such
locks after the work is done (except during error where we free them
at transaction abort) rather than at transaction commit, so one might
say it is better not to associate with transaction state, but not sure
if there is other better place.  Do you have any suggestions?

-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com