From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Neil Conway <neilc(at)samurai(dot)com> |
Cc: | Andrew Dunstan <andrew(at)dunslane(dot)net>, Martijn van Oosterhout <kleptog(at)svana(dot)org>, Islam Hegazy <islheg(at)hotmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: modifying the tbale function |
Date: | 2007-03-19 03:49:42 |
Message-ID: | 20952.1174276182@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Neil Conway <neilc(at)samurai(dot)com> writes:
> Returning control to the backend for every row returned would likely be
> excessive, but you could return once every k rows and get most of the
> benefits of both approaches (k might be on the order of 1000).
However, this still leaves us with no idea how to persuade perl, tcl,
python, et al to cooperate.
I think you are underestimating the cost of suspending/resuming any of
those interpreters, and overestimating the cost of a tuplestore, which
on a per-tuple basis is really pretty cheap. It's quite likely that the
proposed project would produce piddling or negative gains, after
expending a huge amount of work. (A tenth of the effort on optimizing
tuplestore some more would probably be a better investment.)
A cross-check on this theory could be made without a lot of effort: hack
SQL functions to use a tuplestore (fed via the tuplestore destreceiver,
so as not to exit the executor) instead of return-after-every-tuple.
Compare performance. I kinda suspect you'll find it a loss even there.
regards, tom lane
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