| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: [COMMITTERS] pgsql: If we expect a hash join to be performed in multiple batches, |
| Date: | 2009-04-02 20:32:56 |
| Message-ID: | 1238704376.5444.142.camel@ebony.2ndQuadrant |
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| Lists: | pgsql-committers pgsql-hackers |
On Thu, 2009-04-02 at 15:49 -0400, Tom Lane wrote:
> Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> > Can we add "batches=N" to the EXPLAIN output for Hash and/or Hash Join?
>
> Are you talking about expected batches, or actual batches?
Expected batches for EXPLAIN, both for EXPLAIN ANALYZE.
> If the
> former, would it be sufficient to distinguish "1" from "more than 1"?
> If so, maybe changing the node title to "Batched Hash" would do.
Hmmm, knowing the number of batches is beneficial since it helps you to
calculate the required memory to get best performance.
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support
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