| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Justin Pryzby <pryzby(at)telsasoft(dot)com>, Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Subject: | Re: explain HashAggregate to report bucket and memory stats |
| Date: | 2020-04-08 22:24:39 |
| Message-ID: | bbe0ba154d7965a2563839b12dd266a0e0d97521.camel@j-davis.com |
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| Lists: | pgsql-hackers |
On Wed, 2020-04-08 at 16:00 -0500, Justin Pryzby wrote:
> 90% of the initial goal of this patch was handled by instrumentation
> added by
> "hash spill to disk" (1f39bce02), but this *also* adds:
>
> - separate accounting for tuples vs hashtable;
> - number of hash buckets;
> - handles other agg nodes, and bitmap scan;
>
> Should I continue pursuing this patch?
> Does it still serve any significant purpose?
Those things would be useful for me trying to tune the performance and
cost model. I think we need to put some of these things under "VERBOSE"
or maybe invent a new explain option to provide this level of detail,
though.
Regards,
Jeff Davis
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