Re: Improve hash join's handling of tuples with null join keys

I downloaded the patch and tested all join types: inner, left, right, full, semi and anti. Basically my tests all passed. However, I didn't test any case of parallel query.

I have two nit comments:

1. In hashjoin.h, line 76-78, the added comment says "(In the unlikely but supported case of a non-strict join operator, we treat null keys as normal data.)". But I don't see where non-strict join is handled. So, how this patch impact non-strict joins?

2. Two new join states are added: HJ_FILL_OUTER_NULL_TUPLES, HJ_FILL_INNER_NULL_TUPLES. There are existing join states: HJ_FILL_OUTER_TUPLE and HJ_FILL_INNER_TUPLES. They all use "FILL". But I think that "FILL" in HJ_FILL_OUTER_NULL_TUPLES means different from in "HJ_FILL_OUTER_TUPLE". Because HJ_FILL_OUTER_TUPLE means that when returning an outer tuple, it needs to fill in null-extension of inner tables; while HJ_FILL_OUTER_NULL_TUPLES means to return outer tuples that have null join keys. I would suggest something like "APPEND" for the new states: HJ_APPEND_OUTER_NULL_TUPLES and HJ_APPEND_INNER_NULL_TUPLES.

The new status of this patch is: Waiting on Author