| From: | Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> |
|---|---|
| To: | tgl(at)sss(dot)pgh(dot)pa(dot)us |
| Cc: | chris+pg-general(at)netmonger(dot)net, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: View prevents index |
| Date: | 2001-07-12 04:39:07 |
| Message-ID: | 20010712133907B.t-ishii@sra.co.jp |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
> Christopher Masto <chris+pg-general(at)netmonger(dot)net> writes:
> > I guess maybe I'm expecting too much magic optimization.
>
> You're expecting the system to transform
>
> (SELECT foo UNION SELECT bar) WHERE condition
>
> into
>
> (SELECT foo WHERE condition) UNION (SELECT bar WHERE condition)
>
> It's not immediately obvious to me that these are equivalent, or
> perhaps I should say it's not clear under what conditions is the
> transformation legitimate.
Could you tell me in what cases two of above are not equivalent? Or
any specification in the standard that refers to this kind of
transformation for views?
--
Tatsuo Ishii
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