Hello

I am sending a prototype implementation of functions median and
percentile. This implementation is very simple and I moved it to
contrib for this moment - it is more easy maintainable. Later I'll
move it to core.

These functions are relative simple, there are not barrier for
implementation own specific mutations of this functions - so I propose
move to core only basic and well known form of these to core.

postgres=# select median(v) from generate_series(1,10) g(v);
 median
────────
    5.5
(1 row)

Time: 1.475 ms
postgres=# select percentile(v,50) from generate_series(1,10) g(v);
 percentile
────────────
          5
(1 row)

Time: 0.626 ms

This implementation is based on tuplesort and the speed is relative
well - the result from 1000000 rows is less 1 sec.

Regards

Pavel Stehule

Responses

• Re: wip: functions median and percentile at 2010-08-19 14:50:23 from Greg Stark
• Re: wip: functions median and percentile at 2010-09-20 03:47:09 from Hitoshi Harada

pgsql-hackers by date

Next:	From: Robert Haas	Date: 2010-08-19 13:00:23
	Subject: Re: PL/pgsSQL EXECUTE USING INTO
Previous:	From: Pavel Stehule	Date: 2010-08-19 10:45:13
	Subject: Re: proposal: tuplestore, tuplesort aggregate functions

pgsql-rrreviewers by date

Next:	From: Greg Stark	Date: 2010-08-19 14:50:23
	Subject: Re: wip: functions median and percentile
Previous:	From: Kevin Grittner	Date: 2010-08-18 21:45:47
	Subject: CommitFest 2010-07 final report