Re: TransactionIdIsInProgress() cache

Your patch has been added to the PostgreSQL unapplied patches list at:

http://momjian.postgresql.org/cgi-bin/pgpatches

It will be applied as soon as one of the PostgreSQL committers reviews
and approves it.

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Simon Riggs wrote:
> We currently have a single item cache of the last checked TransactionId,
> which optimises the call to TransactionIdDidCommit() during
> HeapTupleSatisfiesMVCC() and partners.
>
> Before we call TransactionIdDidCommit() we always call
> TransactionIdIsInProgress().
>
> TransactionIdIsInProgress() doesn't check the single item cache, so even
> if we have just checked for this xid, we will check it again. Since this
> function takes ProcArrayLock and may be called while holding other locks
> it will improve scalability if we can skip the call, for the cost of an
> integer comparison.
>
> Following patch implements fastpath in TransactionIdIsInProgress() to
> utilise single item cache.
>
> --
> Simon Riggs
> 2ndQuadrant http://www.2ndQuadrant.com

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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://postgres.enterprisedb.com

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