Re: wip: functions median and percentile

Hitoshi Harada <umi.tanuki@gmail.com>

From: Hitoshi Harada <umi.tanuki@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Pavel Stehule <pavel.stehule@gmail.com>, David Fetter <david@fetter.org>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2010-10-01T15:16:03Z
Lists: pgsql-hackers
2010/10/2 Tom Lane <tgl@sss.pgh.pa.us>:
> Hitoshi Harada <umi.tanuki@gmail.com> writes:
>> Another suggestion?
>
> The implementation I would've expected to see is to do the sort and then
> have two code paths for retrieving the median, depending on whether the
> sort result is all in memory or not.
>

Hm? The problem we encountered in the middle of the patch is there is
no chance to call tuplesort_end if median is called in moving frame
window aggregate because final function is called multiple times
during moving. The nearest pattern was array_agg() which uses
on-memory state and throw its responsibility to clear memory to
executor (nodeAgg / nodeWindowAgg). Am I missing something?

Regards,


-- 
Hitoshi Harada