On 10/10/24 17:23, Andrei Lepikhov wrote:
> On 10/10/24 16:02, Tender Wang wrote:
>>
>>
>> Andrei Lepikhov <lepihov@gmail.com <mailto:lepihov@gmail.com>> 于2024
>> 年 > I think this is because find_computable_ec_member() only
>> tries to
>> > match Vars. Maybe we should teach it to also match OpExprs?
>> Looking into that case, I don't understand only one thing:
>> generate_orderedappend_paths decided to try MergeAppend; the
>> create_append_path routine added the Sort cost, but the Sort node
>> itself wasn't added. Maybe the origin problem is the lack of
>> feasibility
>> examinations?
>>
>>
>> Yeah, I'm also curious why only cost Sort but not adding Sort node in
>> create_merge_append_path().
>> The comments say that " We'll need to insert a Sort node, so include
>> cost for that". Does another place
>> insert the Sort node?
> Before inserting the Sort node, we must identify the column
> corresponding to each path key. And here is the problem: IndexScan has
> two elements in the target list, but SeqScan has only one. It already
> looks strange to me. How do we UNION two sources with different numbers
> of resulting columns? It seems to me we have a bug under the Append node.Sorry for the mess: my sentence is totally
wrong:it is the MergeAppend
node with two elements in the target list (the second one is resjunk). I
think I should research the logic of how append arranges its pathkeys
beforehand.
--
regards, Andrei Lepikhov
