| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | depesz(at)depesz(dot)com |
| Cc: | "Dickson S(dot) Guedes" <listas(at)guedesoft(dot)net>, pg-dev <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: generate_series from now to infinity... |
| Date: | 2009-05-17 17:53:22 |
| Message-ID: | 29572.1242582802@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
hubert depesz lubaczewski <depesz(at)depesz(dot)com> writes:
> why is it not limiting generate_series in the second example?
nodeFunctionscan.c sucks the whole SRF output into a tuplestore before
returning any of it. In principle you could do something different for
a value-per-call SRF, but it would require a second whole code path
(or else major refactoring of ExecMakeTableFunctionResult and related
code). The performance implications are unclear too.
I seem to recall there was some discussion of this point when that code
was first written, but nobody bothered to do anything about it.
regards, tom lane
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