From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
---|---|
To: | David Fetter <david(at)fetter(dot)org> |
Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Robert Haas <robertmhaas(at)gmail(dot)com>, Greg Stark <gsstark(at)mit(dot)edu>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Subject: | Re: wip: functions median and percentile |
Date: | 2010-08-19 17:41:57 |
Message-ID: | AANLkTimso=jVibBgQ6Y4gnzOkWb9miOXnhNGy_5UtGJf@mail.gmail.com |
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Lists: | pgsql-hackers pgsql-rrreviewers |
2010/8/19 David Fetter <david(at)fetter(dot)org>:
> On Thu, Aug 19, 2010 at 12:12:12PM -0500, Kevin Grittner wrote:
>> David Fetter <david(at)fetter(dot)org> wrote:
>>
>> > Median may be useful, but we pretty much can't just call it
>> > "median." Instead, we need to call it something like "left_median"
>> > or "arithmetic_median."
>>
>> I think it would be reasonable, and perhaps preferable, to use just
>> "median" for the semantics described in most dictionaries -- for
>> example, this:
>>
>> http://www.merriam-webster.com/dictionary/median
>>
>> If you do a google search for "median" and poke around, you'll find
>> many places where this is the only definition mentioned; the others
>> seem to be rather infrequently used. Why not make the commone usage
>> convenient?
>
> The reason not to is the same reason that MEDIAN doesn't appear in the
> SQL standard, namely that what's common in one field is wrong in
> another.
I think some else. The reason can be more simple - implementation of
median is significantly harder then other aggregates.
I looked there and Oracle11g use "median" in common sense.
Regards
Pavel Stehule
>
> Cheers,
> David.
> --
> David Fetter <david(at)fetter(dot)org> http://fetter.org/
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