| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com> |
| Cc: | Greg Stark <stark(at)enterprisedb(dot)com>, Yoshiyuki Asaba <y-asaba(at)sraoss(dot)co(dot)jp>, Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Common Table Expressions applied; some issues remain |
| Date: | 2009-05-27 03:36:34 |
| Message-ID: | 26465.1243395394@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com> writes:
> 2009/5/27 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
>> I could still see doing what I mentioned in the prior message, which is
>> to flatten CTEs as if they are plain sub-selects when
>>
>> 1. they are non-recursive,
>> 2. they are referenced only once, and
>> 3. they contain no volatile functions.
> And 4. only if the sub-selects use index scan? Or in other cases would
> it be effective?
Uh ... you've got the causality backwards, and I don't see the point of
such a restriction anyway.
regards, tom lane
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