| From: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, 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> |
| Subject: | Re: Re: Request for Patch Feedback: Lag & Lead Window Functions Can Ignore Nulls |
| Date: | 2016-05-30 08:26:00 |
| Message-ID: | CAEZATCVZeVK-Ku8LfawTu5hLkzdajsLtD+CyxCA7OaRV=VWY-w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 23 May 2016 at 17:01, Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> 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.
>
That may be so, but we already support FILTER for all windows
functions as well as aggregates:
https://www.postgresql.org/docs/current/static/sql-expressions.html#SYNTAX-AGGREGATES
https://www.postgresql.org/docs/current/static/sql-expressions.html#SYNTAX-WINDOW-FUNCTIONS
so to be clear, what we're talking about here is just supporting SQL
standard syntax for window functions, rather than adding any new
functionality, right?
> So if we support IGNORE|RESPECT NULLS for anything other than a window
> function, we have to come up with our own semantics.
>
Given that we can already do this using FILTER for aggregates, and
that IGNORE|RESPECT NULLS for aggregates is not part of the SQL
standard, I see no reason to support it.
Regards,
Dean
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