Re: STABLE functions
От | Philip Warner |
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Тема | Re: STABLE functions |
Дата | |
Msg-id | 5.1.0.14.0.20030427115157.02a599d8@mail.rhyme.com.au обсуждение исходный текст |
Ответ на | Re: STABLE functions (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: STABLE functions
|
Список | 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) ---------------------------------------------------------------- Philip Warner | __---_____ Albatross Consulting Pty. Ltd. |----/ - \ (A.B.N. 75 008 659 498) | /(@) ______---_ Tel: (+61) 0500 83 82 81 | _________ \ Fax: (+61) 03 5330 3172 | ___________ | Http://www.rhyme.com.au | / \| | --________-- PGP key available upon request, | / and from pgp5.ai.mit.edu:11371 |/
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