| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alexander Kuzmenkov <a(dot)kuzmenkov(at)postgrespro(dot)ru>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Removing unneeded self joins |
| Date: | 2018-05-16 18:58:40 |
| Message-ID: | 20180516185840.a7crgjho7txxqmi4@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2018-05-16 12:26:48 -0400, Robert Haas wrote:
> Also, I'm not sure that I believe that it's always easy to avoid
> generating such queries.
Yea. There's obviously plenty cases where ORMs just want to make the
database hurt. But especially when building a join between a number of
tables based on various fields, it's not going to be easy for the ORM to
figure out which ones can be safely omitted. It'd need similar
optimization as we'd have to do, without having the infrastructure core
PG has. And then there's, as you say, views etc...
Greetings,
Andres Freund
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