Re: User-defined Operator Pushdown and Collations

Paul Ramsey <pramsey(at)cleverelephant(dot)ca> writes:
> On Sun, Nov 27, 2016 at 9:31 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Why doesn't hs_fdw.h have a collation?

> I think I'm missing something, I cannot find a file like that anywhere.

I was referring to the variable shown in your EXPLAIN.

> With respect to this particular example, is this a case of a very large
> collation hammer getting in the way? Both '->' and '=' are operators that
> would be unaffected by collation, right? They are both just equality-based
> tests. But all operators are getting tested for coherent collation
> behaviour, so they get caught up in the net?

Yeah, we don't know whether the operator actually cares about its input
collation. It'd be possible to be much more liberal if we knew it did
not, but such labeling was not included in the design for the collation
facility. That might've been a mistake ...

regards, tom lane