Re: BUG #16583: merge join on tables with different DB collation behind postgres_fdw fails

The following review has been posted through the commitfest application:
make installcheck-world: tested, passed
Implements feature: tested, passed
Spec compliant: not tested
Documentation: tested, passed

Greetings,
I learned about the patch and read your discussions. I'm not sure why this patch has not been discussed now. In short, I think it's beneficial to submit it as a temporary solution.
Another thing I want to know is whether these codes can be simplified:
- if (state > outer_cxt->state)
+ if (collation == outer_cxt->collation &&
+ ((state == FDW_COLLATE_UNSAFE &&
+ outer_cxt->state == FDW_COLLATE_SAFE) ||
+ (state == FDW_COLLATE_SAFE &&
+ outer_cxt->state == FDW_COLLATE_UNSAFE)))
+ {
+ outer_cxt->state = FDW_COLLATE_SAFE;
+ }
+ else if (state > outer_cxt->state)

If the state is determined by the collation, when the collations are equal, do we just need to judge the state not equal to FDW_COLLATE_NONE?