| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Greg Sabino Mullane <greg(at)turnstep(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Re: [COMMITTERS] pgsql: Rewrite GEQO's gimme_tree function so that it always finds a |
| Date: | 2009-12-03 03:53:36 |
| Message-ID: | 29192.1259812416@sss.pgh.pa.us |
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| Lists: | pgsql-committers pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> Well, when I was testing, I believe I observed that an n-way join with
> 1 cross join was slower to plan than an n-way join with no cross
> joins. ISTM that it should actually be faster, because you should
> plan it like an (n-1)-way join and then do the cross join at the end.
It's not entirely clear to me what case you're describing, but I wonder
whether this was a "flat" join problem or restricted by the collapse
limits.
regards, tom lane
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