Re: [HACKERS] pg_serial early wraparound

From: Stephen Frost <sfrost(at)snowman(dot)net>
To: Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>
Cc: Anastasia Lubennikova <lubennikovaav(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Thomas Munro <munro(at)ip9(dot)org>
Subject: Re: [HACKERS] pg_serial early wraparound
Date: 2018-01-22 22:50:14
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* Thomas Munro (thomas(dot)munro(at)enterprisedb(dot)com) wrote:
> On Wed, Jun 28, 2017 at 1:11 PM, Thomas Munro
> <thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> > On Sat, Mar 25, 2017 at 7:27 AM, Thomas Munro
> > <thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> >> On Sat, Mar 25, 2017 at 3:11 AM, Anastasia Lubennikova
> >> <lubennikovaav(at)gmail(dot)com> wrote:
> >>> You claim that SLRUs now support five digit segment name, while in slru.h
> >>> at current master I see the following:
> >>>
> >>> * Note: slru.c currently assumes that segment file names will be four hex
> >>> * digits. This sets a lower bound on the segment size (64K transactions
> >>> * for 32-bit TransactionIds).
> >>> */
> >
> > I've now complained about that comment in a separate thread.
> >
> >> It's not urgent, it's just cleanup work, so I've now moved it to the
> >> next commitfest. I will try to figure out a new way to demonstrate
> >> that it works correctly without having to ask a review[er] to disable
> >> any assertions. Thanks again.
> Rebased again, now with a commit message. That assertion has since
> been removed (commit ec99dd5a) so the attached test script can once
> again be used to see the contents of pg_serial as the xid goes all the
> way around, if you build with TEST_OLDSERXID defined so that
> predicate.c forces information about xids out to pg_serial.

I've taken a look through this and it seems pretty reasonable. Would be
great to have someone actually try to duplicate the testing that Thomas
did (though I have little doubt that it works as described) and get it
to Ready-For-Committer state.

Anastasia, thanks for the previous review, any chance you could try
again with the latest patch (against the current state of git)?



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