| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | Peter Geoghegan <peter(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: logical decoding - GetOldestXmin |
| Date: | 2012-12-13 22:29:06 |
| Message-ID: | CA+TgmoZz-t+6SrYOUbhyxi80_M0HNsh_Un0AcMjSysE5nM7oMg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Dec 13, 2012 at 3:03 PM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> It moves a computation of the sort of:
>
> result -= vacuum_defer_cleanup_age;
> if (!TransactionIdIsNormal(result))
> result = FirstNormalTransactionId;
>
> inside ProcArrayLock. But I can't really imagine that to be relevant...
I can. Go look at some of the 9.2 optimizations around
GetSnapshotData(). Those made a BIG difference under heavy
concurrency and they were definitely micro-optimization. For example,
the introduction of NormalTransactionIdPrecedes() was shockingly
effective.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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