| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> |
| Cc: | Josh Berkus <josh(at)agliodbs(dot)com>, Michael Fuhr <mike(at)fuhr(dot)org>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Functionscan estimates |
| Date: | 2005-04-09 04:00:56 |
| Message-ID: | 19038.1113019256@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers 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
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Bruce Momjian | 2005-04-09 04:06:43 | Re: DELETE ... USING |
| Previous Message | Tom Lane | 2005-04-09 03:40:28 | Re: Optimizing maximum/minimum queries (yet again) |
| From | Date | Subject | |
|---|---|---|---|
| Next Message | PFC | 2005-04-09 11:25:47 | Re: Functionscan estimates |
| Previous Message | Alvaro Herrera | 2005-04-08 23:57:31 | Re: Functionscan estimates |