Horton

Re: [Patch] ALTER SYSTEM READ ONLY

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Amul Sul <sulamul@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Ibrar Ahmed <ibrar.ahmad@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Prabhat Sahu <prabhat.sahu@enterprisedb.com>
Date: 2021-05-13T09:26:29Z
Lists: pgsql-hackers 
On Thu, May 13, 2021 at 2:54 PM Amul Sul <sulamul@gmail.com> wrote:
>
> On Thu, May 13, 2021 at 12:36 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> >
> > On Wed, May 12, 2021 at 5:55 PM Amul Sul <sulamul@gmail.com> wrote:
> > >
> >
> > Thanks for the updated patch, while going through I noticed this comment.
> >
> > + /*
> > + * WAL prohibit state changes not allowed during recovery except the crash
> > + * recovery case.
> > + */
> > + PreventCommandDuringRecovery("pg_prohibit_wal()");
> >
> > Why do we need to allow state change during recovery?  Do you still
> > need it after the latest changes you discussed here, I mean now
> > XLogAcceptWrites() being called before sending barrier to backends.
> > So now we are not afraid that the backend will write WAL before we
> > call XLogAcceptWrites().  So now IMHO, we don't need to keep the
> > system in recovery until pg_prohibit_wal(false) is called, right?
> >
>
> Your understanding is correct, and the previous patch also does the same, but
> the code comment is wrong.  Fixed in the attached version, also rebased for the
> latest master head. Sorry for the confusion.

Great thanks.  I will review the remaining patch soon.

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. Initialize variable to placate compiler.

  2. StartupXLOG: Don't repeatedly disable/enable local xlog insertion.

  3. StartupXLOG: Call CleanupAfterArchiveRecovery after XLogReportParameters.

  4. Postpone some end-of-recovery operations related to allowing WAL.

  5. Refactor some end-of-recovery code out of StartupXLOG().

  6. Re-enable contrib/bloom's TAP tests.

  7. Remove unnecessary call to ReadCheckpointRecord().

  8. Allow for error or refusal while absorbing a ProcSignalBarrier.

  9. Add comment to explain an unused function parameter

  10. Extend the ProcSignal mechanism to support barriers.

  11. At promotion, don't leave behind a partial segment on the old timeline.