| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
| Cc: | Stephen Frost <sfrost(at)snowman(dot)net>, Nicholas White <n(dot)j(dot)white(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Troels Nielsen <bn(dot)troels(at)gmail(dot)com>, Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> |
| Subject: | Re: Re: Request for Patch Feedback: Lag & Lead Window Functions Can Ignore Nulls |
| Date: | 2016-05-23 16:01:37 |
| Message-ID: | CAMp0ubfEyKczTaAvOyBcki_Fjbt15gYWL1+_grYiC=A5TsUXaA@mail.gmail.com |
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On Fri, May 20, 2016 at 1:41 PM, David G. Johnston
<david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
> How does the relatively new FILTER clause play into this, if at all?
My interpretation of the standard is that FILTER is not allowable for
a window function, and IGNORE|RESPECT NULLS is not allowable for an
ordinary aggregate.
So if we support IGNORE|RESPECT NULLS for anything other than a window
function, we have to come up with our own semantics.
> We already have "STRICT" for deciding whether a function processes nulls.
> Wouldn't this need to exist on the "CREATE AGGREGATE"
STRICT defines behavior at DDL time. I was suggesting that we might
want a DDL-time flag to indicate whether a function can make use of
the query-time IGNORE|RESPECT NULLS option. In other words, most
functions wouldn't know what to do with IGNORE|RESPECT NULLS, but
perhaps some would if we allowed them the option.
Perhaps I didn't understand your point?
Regards,
Jeff Davis
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