Re: CLOG contention

Excerpts from Robert Haas's message of mié dic 21 13:18:36 -0300 2011:

> There may be workloads where that will help, but it's definitely not
> going to cover all cases.  Consider my trusty
> pgbench-at-scale-factor-100 test case: since the working set fits
> inside shared buffers, we're only writing pages at checkpoint time.
> The contention happens because we randomly select rows from the table,
> and whatever row we select hasn't been examined since it was last
> updated, and so it's unhinted.  But we're not reading the page in:
> it's already in shared buffers, and has never been written out.  I
> don't see any realistic way to avoid the CLOG lookups in that case:
> nobody else has had any reason to touch that page in any way since the
> tuple was first written.

Maybe we need a background "tuple hinter" process ...

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Álvaro Herrera <alvherre@commandprompt.com>
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