(2014/04/10 22:25), Tom Lane wrote:
> Etsuro Fujita <fujita.ets...@lab.ntt.co.jp> writes:
>> (2014/04/10 0:08), Tom Lane wrote:
>>> TBH I think that's barely the tip of the iceberg of cases where this
>>> patch will get the wrong answer.
>>> Also, I don't see it doing anything to check the ordering
>>> of multiple index columns
>> I think that the following code in index_pathkeys_are_extensible() would
>> check the ordering:
>> +    if (!pathkeys_contained_in(pathkeys, root->query_pathkeys))
>> +            return false;
> Hm ... if you're relying on that, then what's the point of the new loop
> at all?

The point is that from the discussion [1], we allow the index pathkeys
to be extended to query_pathkeys if each *remaining* pathkey in
query_pathkey is a Var belonging to the indexed relation.  The code is
confusing, though.  Sorry, that is my faults.


[1] http://www.postgresql.org/message-id/29637.1389064...@sss.pgh.pa.us

Best regards,
Etsuro Fujita

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