| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | zuming(dot)jiang(at)inf(dot)ethz(dot)ch, pgsql-bugs(at)lists(dot)postgresql(dot)org |
| Subject: | Re: BUG #17976: Inconsistent results of SELECT using CASE WHEN clause |
| Date: | 2023-06-14 23:55:27 |
| Message-ID: | 2025424.1686786927@sss.pgh.pa.us |
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| Lists: | pgsql-bugs |
David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> The first bad commit seems to be b448f1c8
Yeah, I think the proximate cause is the removal of the delay_upper_joins
restrictions in analyzejoins.c. That allows us to remove the join to
ref_0, which prior versions didn't do; but then that exposes the need to
clean up dead references in EquivalenceClasses. I'm wondering a bit
now if there are variants of this that'd fail in pre-v16 branches.
It's not obvious to me offhand why delay_upper_joins would have prevented
all cases where a removable rel could be mentioned in an EquivalenceClass
member (presumably via the ph_rels set of a PHV).
regards, tom lane
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