Re: Functionscan estimates

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От Tom Lane
Тема Re: Functionscan estimates
Дата
Msg-id 19038.1113019256@sss.pgh.pa.us
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Ответ на Re: Functionscan estimates  (Alvaro Herrera <alvherre@dcc.uchile.cl>)
Ответы Re: Functionscan estimates  (PFC <lists@boutiquenumerique.com>)
Re: Functionscan estimates  ("Jim C. Nasby" <decibel@decibel.org>)
Re: Functionscan estimates  (Neil Conway <neilc@samurai.com>)
Список pgsql-performance
Not too many releases ago, there were several columns in pg_proc that
were intended to support estimation of the runtime cost and number of
result rows of set-returning functions.  I believe in fact that these
were the remains of Joe Hellerstein's thesis on expensive-function
evaluation, and are exactly what he was talking about here:
http://archives.postgresql.org/pgsql-hackers/2002-06/msg00085.php

But with all due respect to Joe, I think the reason that stuff got
trimmed is that it didn't work very well.  In most cases it's
*hard* to write an estimator for a SRF.  Let's see you produce
one for dblink() for instance ...

            regards, tom lane

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