| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | David Fetter <david(at)fetter(dot)org> |
| Cc: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: proposal: tuplestore, tuplesort aggregate functions |
| Date: | 2010-08-18 14:39:33 |
| Message-ID: | 29257.1282142373@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
David Fetter <david(at)fetter(dot)org> writes:
> Apart from the medians, which "median-like" aggregates do you have in
> mind to start with? If you can provide examples of "median-like"
> aggregates that people might need to implement as user-defined
> aggregates, or other places where people would use this machinery, it
> will make your case stronger for this refactoring.
There would be plenty of scope to re-use the machinery without any
SQL-level extensions. All you need is a polymorphic aggregate
transition function that maintains a tuplestore or whatever.
I don't see that extra syntax in CREATE AGGREGATE is really buying
much of anything.
regards, tom lane
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