Re: Is this a problem in GenericXLogFinish()?

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Michael Paquier <michael(at)paquier(dot)xyz>
Cc: "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com>, Alexander Lakhin <exclusion(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Jeff Davis <pgsql(at)j-davis(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Is this a problem in GenericXLogFinish()?
Date: 2024-04-05 05:47:03
Message-ID: CAA4eK1+ayneM-8mSRC0iWpDMnm39EwDoqgiOCSqrrMLcdnUnAA@mail.gmail.com
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On Fri, Apr 5, 2024 at 9:56 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>
> On Wed, Feb 07, 2024 at 06:42:21PM +0900, Michael Paquier wrote:
> > On Wed, Feb 07, 2024 at 02:08:42PM +0530, Amit Kapila wrote:
> > > Thanks for the report and looking into it. Pushed!
> >
> > Thanks Amit for the commit and Kuroda-san for the patch!
>
> I have been pinged about this thread and I should have looked a bit
> closer, but wait a minute here.
>
> There is still some divergence between the code path of
> _hash_freeovflpage() and the replay in hash_xlog_squeeze_page() when
> squeezing a page: we do not set the LSN of the write buffer if
> (xlrec.ntups <= 0 && xlrec.is_prim_bucket_same_wrt &&
> !xlrec.is_prev_bucket_same_wrt) when generating the squeeze record,
> but at replay we call PageSetLSN() on the write buffer and mark it
> dirty in this case. Isn't that incorrect?
>

Agreed. We will try to reproduce this.

> It seems to me that we
> should be able to make the conditional depending on the state of the
> xl_hash_squeeze_page record, no?
>

I think we can have a flag like mod_buf and set it in both the
conditions if (xldata->ntups > 0) and if
(xldata->is_prev_bucket_same_wrt). If the flag is set then we can set
the LSN and mark buffer dirty.

--
With Regards,
Amit Kapila.

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