| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Dimitri Fontaine <dim(at)hi-media(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: *_collapse_limit, geqo_threshold |
| Date: | 2009-07-07 22:33:19 |
| Message-ID: | 286.1247005999@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Jul 7, 2009, at 4:56 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> My own thought is that from_collapse_limit has more justification,
> That's pretty much where I am with it, too. The feature I was
> referring to was not the collapse limits, but the ability to
> explicitly specify the join order, which perhaps could be a useful
> tool for reducing planning time or coping with bad estimates if you
> could do it for only some of the joins in the query, but which we're
> instead proposing to keep as an all-or-nothing flag.
It's pretty much all-or-nothing now: the GUC does not give you any sort
of useful control over *which* joins are reorderable.
regards, tom lane
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