| From: | Philip Warner <pjw(at)rhyme(dot)com(dot)au> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Joachim Wieland <jwieland(at)kawo2(dot)rwth-aachen(dot)de> |
| Cc: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: STABLE functions |
| Date: | 2003-04-27 01:53:27 |
| Message-ID: | 5.1.0.14.0.20030427115157.02a599d8@mail.rhyme.com.au |
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| Lists: | pgsql-hackers |
At 11:13 AM 25/04/2003 -0400, Tom Lane wrote:
>The point is that the system *may* choose to evaluate f() only once,
>not that it *must* do so. The classification exists to make it valid
>to use an indexscan on "col".
So just for my own understanding, the optimizer does not know that it can
treat a STABLE function f as constant inside an outer loop of t1 in this query:
select * from t1,t2 where t2.f1 = f(t1.f1)
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