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help / color / mirror / Atom feedFrom: Melanie Plageman <[email protected]>
To: Andres Freund <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Cc: [email protected]
Cc: Thomas Munro <[email protected]>
Cc: Heikki Linnakangas <[email protected]>
Cc: Noah Misch <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Michael Paquier <[email protected]>
Subject: Re: Buffer locking is special (hints, checksums, AIO writes)
Date: Tue, 25 Nov 2025 16:23:04 -0500
Message-ID: <CAAKRu_apB8+6dDaDBE+tPv8H8rmta3JHomTKFh7VEZK-LYga1g@mail.gmail.com> (raw)
In-Reply-To: <uuukiok2b5gbbae6blokwim2ohxxvp5235epd5zrbc5d3fojb6@vsqee77athye>
References: <6kmid26do57ykqfpvq6iieniy4djsymhrypkjccazq5g4bbe6a@2y6owwv7qpex>
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<6rgb2nvhyvnszz4ul3wfzlf5rheb2kkwrglthnna7qhe24onwr@vw27225tkyar>
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<3nce7i72ayzkunai6mkz24ckbxk74jodz4ua2chcdrwppxlxcd@w6x5kfkjrkru>
<CAAKRu_bsQ5KmtAjFsOEHGZCiirp_wgTPyfAQfsyJsGU=g7rkCQ@mail.gmail.com>
<uuukiok2b5gbbae6blokwim2ohxxvp5235epd5zrbc5d3fojb6@vsqee77athye>
On Tue, Nov 25, 2025 at 3:46 PM Andres Freund <[email protected]> wrote:
>
>
> > > > I presume you didn't do this because HeapTupleSatisifiesMVCC() for
> > > > SNAPSHOT_MVCC calls the non-batch version (and, of course,
> > > > HeapTupleSatisifiesVisibility() is the much more common case).
> > > >
> > > > if (TransactionIdIsValid(xid))
> > > > {
> > > > if (BufferIsPermanent(buffer))
> > > > {
> > > > /* NB: xid must be known committed here! */
> > > > XLogRecPtr commitLSN = TransactionIdGetCommitLSN(xid);
> > > >
> > > > if (XLogNeedsFlush(commitLSN) &&
> > > > BufferGetLSNAtomic(buffer) < commitLSN)
> > > > {
> > > > /* not flushed and no LSN interlock, so don't
> > > > set hint */
> > > > return; false;
> > > > }
> > > > }
> > > > }
> > > >
> > > > Separately, I was thinking, should we assert here about having the
> > > > right lock type?
> > >
> > > Not sure I get what assert of what locktype where?
> >
> > In SetHintBitsExt() that we have share-exclusive or above.
>
> We *don't* necessarily hold that though, it'll just be acquired by
> BufferBeginSetHintBits(). Or do you mean in the SHB_ENABLED case?
Yea, in the enabled case. Also, can't we skip the whole
if (TransactionIdIsValid(xid))
{
if (BufferIsPermanent(buffer))
{
/* NB: xid must be known committed here! */
XLogRecPtr commitLSN = TransactionIdGetCommitLSN(xid);
if (XLogNeedsFlush(commitLSN) &&
BufferGetLSNAtomic(buffer) < commitLSN)
{
/* not flushed and no LSN interlock, so don't set hint */
return;
}
}
}
part if state is SHB_DISABLED?
- Melanie
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Subject: Re: Buffer locking is special (hints, checksums, AIO writes)
In-Reply-To: <CAAKRu_apB8+6dDaDBE+tPv8H8rmta3JHomTKFh7VEZK-LYga1g@mail.gmail.com>
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