Re: Request for Patch Feedback: Lag & Lead Window Functions Can Ignore Nulls

From: Nicholas White <n(dot)j(dot)white(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Request for Patch Feedback: Lag & Lead Window Functions Can Ignore Nulls
Date: 2013-03-23 22:25:02
Message-ID: CA+=vxNbP3kLHfSN839z0PRCTjRhpfWxb30ERx1pQohNhQ4261g@mail.gmail.com
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Thanks - I've added it here:
https://commitfest.postgresql.org/action/patch_view?id=1096 .

I've also attached a revised version that makes IGNORE and RESPECT
UNRESERVED keywords (following the pattern of NULLS_FIRST and NULLS_LAST).

Nick

On 23 March 2013 14:34, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Nicholas White <n(dot)j(dot)white(at)gmail(dot)com> writes:
> > The SQL standard defines a RESPECT NULLS or IGNORE NULLS option for lead,
> > lag, [...]. This is not implemented in PostgreSQL
> > (http://www.postgresql.org/docs/devel/static/functions-window.html)
> > I've had a go at implementing this, and I've attached the resulting
> patch.
> > It's not finished yet, but I was hoping to find out if my solution is
> along
> > the right lines.
>
> Since we're trying to get 9.3 to closure, this patch probably isn't
> going to get much attention until the 9.4 development cycle starts
> (in a couple of months, likely). In the meantime, please add it to
> the next commitfest list so we remember to come back to it:
> https://commitfest.postgresql.org/action/commitfest_view?id=18
>
> One comment just from a quick eyeball look is that we really hate
> adding new keywords that aren't UNRESERVED, because that risks
> breaking existing applications. Please see if you can refactor the
> grammar to make those new entries unreserved.
>
> regards, tom lane
>

Attachment Content-Type Size
lead-lag-ignore-nulls.patch application/octet-stream 17.1 KB

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