Re: Postgres_fdw join pushdown - wrong results with whole-row reference

On 2016/06/24 15:44, Ashutosh Bapat wrote:
>>
>> I think the proposed idea of applying record::text explicit coercion to a
>> whole-row reference in the IS NOT NULL condition in the CASE WHEN
>> conversion would work as expected as you explained, but I'm concerned that
>> the cost wouldn't be negligible when the foreign table has a lot of columns.
>
> That's right, if the foreign server doesn't optimize the case for IS NOT
> NULL, which it doesn't :)
>
> I am happy to use any cheaper means e.g a function which counts number of
> columns in a record. All we need here is a way to correctly identify when a
> record is null and not null in the way we want (as described upthread). I
> didn't find any quickly. Do you have any suggestions?

I'm now starting to wonder if it would be outright wrong to just use the
alias names of corresponding foreign tables directly for whole-row
references?  So, instead of these in target lists of remote queries:

SELECT CASE WHEN (r1.*)::text IS NOT NULL THEN ROW (r1.*) END, ...