| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
| Cc: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: support for NEXT VALUE FOR expression |
| Date: | 2016-08-17 04:19:21 |
| Message-ID: | 18876.1471407561@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> writes:
> On Wed, Aug 17, 2016 at 3:52 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> We discussed this before and concluded that NEXT VALUE FOR is in fact
>> *not* an exact semantic equivalent of nextval():
>> https://www.postgresql.org/message-id/14790.1083955136%40sss.pgh.pa.us
> And also again 10 years later when I proposed it :-)
> https://www.postgresql.org/message-id/flat/CADLWmXUY2oo4XObQWF3yPUSK%3D5uEiSV%3DeTyLrnu%3DRzteOy%2B3Lg%40mail.gmail.com
And that links to yet another thread, from 2002 ;-)
The 2004 thread does contain some speculation about how to implement the
spec's semantics. It seems like the first problem is nailing down what
is meant by "once per row", particularly in cases with nested execution
contexts.
regards, tom lane
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