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Re: Review: listagg aggregate

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Takahiro Itagaki <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, "David E(dot) Wheeler" <david(at)kineticode(dot)com>, "pgsql-hackers(at)postgresql(dot)org Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Review: listagg aggregate
Date: 2010-01-29 07:43:48
Message-ID: 162867791001282343o472f6dfck6f5bd9d98b09acfd@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
2010/1/28 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
>> with get_fn_expr_arg_stable() we are able to fix second parameter
>> without some performance issues.
>
> No, that will create its own performance issues ---
> get_fn_expr_arg_stable isn't especially cheap.
> If there were a really strong reason why we had to do it,
> then I'd agree, but frankly the argument for disallowing
> a variable delimiter is too thin.

it could be called only once. But I agree, so could be better, check
it in parser time.

ok - I am only one who like original behave - so I  am withdrawing.
Robert, If you like, please commit Itagaki's patch. + add note about
behave when second parameter isn't stable.

Regards
Pavel Stehule



>
>                        regards, tom lane
>

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