| From: | "Joshua Tolley" <eggyknap(at)gmail(dot)com> |
|---|---|
| To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | "Lawrence, Ramon" <ramon(dot)lawrence(at)ubc(dot)ca>, pgsql-hackers(at)postgresql(dot)org, "Bryce Cutt" <pandasuit(at)gmail(dot)com> |
| Subject: | Re: Proposed Patch to Improve Performance of Multi-Batch Hash Join for Skewed Data Sets |
| Date: | 2008-11-05 15:22:42 |
| Message-ID: | e7e0a2570811050722p5655f163v1dd492bd259c2ec@mail.gmail.com |
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| Lists: | pgsql-hackers |
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On Wed, Nov 5, 2008 at 8:20 AM, Tom Lane wrote:
> Joshua Tolley writes:
>> On Mon, Oct 20, 2008 at 03:42:49PM -0700, Lawrence, Ramon wrote:
>>> We propose a patch that improves hybrid hash join's performance for large
>>> multi-batch joins where the probe relation has skew.
>
>> I also recommend modifying docs/src/sgml/config.sgml to include the
>> enable_hashjoin_usestatmcvs option.
>
> If the patch is actually a win, why would we bother with such a GUC
> at all?
>
> regards, tom lane
Good point. Leaving it in place for patch review purposes is useful,
but we can probably lose it in the end.
- - Josh / eggyknap
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