Re: *_collapse_limit, geqo_threshold - Mailing list pgsql-hackers

From Tom Lane
Subject Re: *_collapse_limit, geqo_threshold
Date
Msg-id 286.1247005999@sss.pgh.pa.us
Whole thread Raw
In response to Re: *_collapse_limit, geqo_threshold  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: *_collapse_limit, geqo_threshold
List pgsql-hackers
Robert Haas <robertmhaas@gmail.com> writes:
> On Jul 7, 2009, at 4:56 PM, Tom Lane <tgl@sss.pgh.pa.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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