| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | "Lawrence, Ramon" <ramon(dot)lawrence(at)ubc(dot)ca> |
| Cc: | Bryce Cutt <pandasuit(at)gmail(dot)com>, Joshua Tolley <eggyknap(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Proposed Patch to Improve Performance of Multi-BatchHash Join for Skewed Data Sets |
| Date: | 2009-02-19 04:28:02 |
| Message-ID: | 603c8f070902182028y6b4d795ch3e3902016c9217f9@mail.gmail.com |
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| Lists: | pgsql-hackers |
> At this point, we await further feedback on what is necessary to get
> this patch accepted. We would also like to thank Josh and Robert again
> for their review time.
I think what we need here is some very simple testing to demonstrate
that this patch demonstrates a speed-up even when the inner side of
the join is a joinrel rather than a baserel. Can you suggest a single
query against the skewed TPCH dataset that will result in two or more
multi-batch hash joins? If so, it should be a simple matter to run
that query with and without the patch and verify that the former is
faster than the latter.
Thanks,
...Robert
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