Horton

Re: BUG #18652: Planner can not find pathkey item to sort for query with expression and expression index

Andrei Lepikhov <lepihov@gmail.com>

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From: Andrei Lepikhov <lepihov@gmail.com>
To: Richard Guo <guofenglinux@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>
Cc: exclusion@gmail.com, pgsql-bugs@lists.postgresql.org
Date: 2024-10-11T04:25:47Z
Lists: pgsql-bugs

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On 10/10/24 10:52, Richard Guo wrote:
> On Thu, Oct 10, 2024 at 5:43 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> It looks like we are generating a Path tree in which one of the
>> inputs to a MergeAppend is a plain unsorted seqscan, which'd
>> be all right except it doesn't expose the required sort value
>> in its targetlist.
> I think this is because find_computable_ec_member() only tries to
> match Vars.  Maybe we should teach it to also match OpExprs?
Why not look if some entry of the TargetList contains the var? Something 
like attached?
If I understand correctly, MergeAppend will still add a resjunk column 
and Sort according to the column.

-- 
regards, Andrei Lepikhov

Commits

  1. Correctly identify which EC members are computable at a plan node.

  2. Support MergeAppend plans, to allow sorted output from append relations.