Re: wip: functions median and percentile

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>
Cc: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, David Fetter <david(at)fetter(dot)org>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: wip: functions median and percentile
Date: 2010-10-01 14:43:47
Message-ID: 13146.1285944227@sss.pgh.pa.us
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers pgsql-rrreviewers

Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com> writes:
> 2010/10/1 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
>> If this patch tries to force the entire sort to happen in memory,
>> it is not committable.

> What about array_agg()? Doesn't it exceed memory even if the huge data come in?

Yeah, but for array_agg the user should be expecting a result of
approximately the size of the whole input, so if he overruns memory he
hasn't got a lot of room to complain. There is no reason for a user to
expect that median or percentile will fall over on large input, and
every reason to expect them to be more robust than that.

regards, tom lane

In response to

Responses

Browse pgsql-hackers by date

  From Date Subject
Next Message Robert Haas 2010-10-01 14:44:44 Re: wip: functions median and percentile
Previous Message Robert Haas 2010-10-01 14:41:39 Re: recovery.conf location

Browse pgsql-rrreviewers by date

  From Date Subject
Next Message Robert Haas 2010-10-01 14:44:44 Re: wip: functions median and percentile
Previous Message Hitoshi Harada 2010-10-01 14:11:08 Re: wip: functions median and percentile