From: | Vadim Mikheev <vadim(at)krs(dot)ru> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] Why not sub-selects in targetlists? |
Date: | 1999-08-30 01:39:50 |
Message-ID: | 37C9E0E6.AFD53DBE@krs.ru |
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Lists: | pgsql-hackers |
Tom Lane wrote:
>
> For some reason we currently support sub-SELECT expressions only
> in WHERE and HAVING clauses, not in the target list of a SELECT.
> Does anyone know why this is?
>
> There are a number of places in the planner/optimizer that would need
> to be fixed to make it happen, but the changes are utterly trivial
> (calling certain transformation routines on the targetlist as well as
> for WHERE and HAVING ... probably about a dozen lines total ...).
> And a quick look at the executor doesn't show any reason why it would
> have a problem, either. Is there something fundamental that I'm
> missing? If not, why wasn't this done to begin with?
As usual, I just hadn't time to do more than it's done for
6.3.X -:) Subselects were not in my TODO list, I made base
implementation because of there were many requests for them.
BTW, please don't forget subselects in FROM.
Vadim
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