| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jim Nasby <jim(dot)nasby(at)openscg(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem) |
| Date: | 2018-04-01 14:54:34 |
| Message-ID: | CAKJS1f9ee7MSf30i=a8REuuDkQdkeSV+WERu0VYkUQjxH9w1qw@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
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| Lists: | pgsql-hackers |
On 30 March 2018 at 15:05, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> + * To allow join removal to happen, we can't reference the CTID column
>> + * of an otherwise-removable relation.
>
> A brief hint why wouldn't hurt.
Maybe something like:
/*
* Join removal is only ever possible when no columns of the
to-be-removed relation
* are referenced. If we added the CTID here then we could
inadvertently disable join
* removal. We'll need to delay adding the CTID until after join
removal takes place.
*/
(I've not read the code, just the thread)
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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