Re: WIP patch for hint bit i/o mitigation

From: Jeff Davis <pgsql(at)j-davis(dot)com>
To: Merlin Moncure <mmoncure(at)gmail(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Atri Sharma <atri(dot)jiit(at)gmail(dot)com>
Subject: Re: WIP patch for hint bit i/o mitigation
Date: 2012-11-16 00:42:15
Message-ID: 1353026535.14335.89.camel@sussancws0025
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On Tue, 2012-11-06 at 17:55 -0600, Merlin Moncure wrote:
> So given that -- the patch simple adds an extra check when/where hint
> bit status is checked in the visibility routines (currently, only
> HeapTupleSatisfiesMVCC is done but all the applicable visibility
> routines should be done). Basically, the way it works is like this:
>
> *) is hint bit set?
> *) if not? does the examined xid match the last examined one?
> *) if so, and the cached hint bit matches the one want, proceeed as if
> hint bit was set

Can you clarify the difference between this and
cachedFetchXid/cachedFetchXidStatus? Do we need to keep those if your
patch is accepted?

Regards,
Jeff Davis

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