From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Ben <midfield(at)gmail(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: contsel and gist |
Date: | 2010-10-28 17:50:24 |
Message-ID: | 23452.1288288224@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Ben <midfield(at)gmail(dot)com> writes:
> my guess is that it has to do with the selectivity of the @> operator. i've looked and noticed that the selectivity functions for @> and other period operators are basically stubs, with constant selectivity. my questions are :
> 1 - am i wrong in my assessment? is the constant contsel, areasel, etc hurting us?
The stub selectivity functions definitely suck.
> 2 - how hard would it be to implement contsel et al for period data types?
If it were easy, it'd likely have been done already :-(
However, having said that: the constant value of the stub contsel
function is intended to be small enough to encourage use of an
indexscan. Maybe we just need to decrease it a bit more. Have you
investigated what the cutover point is for your queries?
regards, tom lane
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