| From: | Richard Guo <riguo(at)pivotal(dot)io> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Pulling up direct-correlated ANY_SUBLINK |
| Date: | 2019-09-12 02:59:24 |
| Message-ID: | CAN_9JTx4Xp4o+7uGtBgQxCon5nnF9ZXF_GSV-vY18YSW8xSAYg@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hi Tom,
On Tue, Sep 10, 2019 at 9:48 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> > Can we try to pull up direct-correlated ANY SubLink with the help of
> > LATERAL?
>
> Perhaps. But what's the argument that you'd end up with a better
> plan? LATERAL pretty much constrains things to use a nestloop,
> so I'm not sure there's anything fundamentally different.
>
This is a point I didn't think of. In that case if the pull-up mostly
results in a nestloop then we cannot make sure we will get a better
plan. Thank you for pointing it out.
Thanks
Richard
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