| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | David Rowley <dgrowley(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Dilip kumar <dilip(dot)kumar(at)huawei(dot)com> |
| Subject: | Re: Allowing join removals for more join types |
| Date: | 2014-06-26 09:27:30 |
| Message-ID: | CA+U5nMKjMHq9LbZC+wTG9eLjAMQr5=ppMda=w55b57w8ox=CjQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 26 June 2014 10:01, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
>> Did you comment on the transitive closure question? Should we add a
>> test for that, whether or not it works yet?
>>
>
> In my previous email.
>
> I could change the the following to use c.id in the targetlist and group by
> clause, but I'm not really sure it's testing anything new or different.
>
> EXPLAIN (COSTS OFF)
> SELECT a.id FROM a
> LEFT JOIN (SELECT b.id,1 as dummy FROM b INNER JOIN c ON b.id = c.id GROUP
> BY b.id) b ON a.id = b.id AND b.dummy = 1;
OK, agreed, no need to include.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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