Re: postgres_fdw bug in 9.6

Probably we should use "could not be created" instead of "was not created"
in "... a local path suitable for EPQ checks was not created".

"outer_path should not require relations from inner_path" may be reworded
as "outer paths should not be parameterized by the inner relations".

"neither path should require relations from the other path" may be reworded
as "neither path should be parameterized by the the other joining relation".

> While the comment below mentions ON true, the testcase you have added is
>> for ON
>> false. Either the testcase should change or this comment. That raises
>> another
>> question, what happens when somebody does FULL JOIN ON false?
>> + * If special case: for "x FULL JOIN y ON true",
>> there
>>
>
> FULL JOIN ON FALSE would be handled the same way as FULL JOIN ON TRUE, so
> I think we should rewrite that comment into something like this: If special
> case: for "x FULL JOIN y ON true" or "x FULL JOIN y ON false"...
>

Ok.

>
> Why JOIN_RIGHT is being treated differently from JOIN_LEFT? We should be
>> able
>> to create a nested loop join for JOIN_RIGHT?
>> + case JOIN_RIGHT:
>> + case JOIN_FULL:
>>
>
> I don't think so, because nestloop joins aren't supported for JOIN_RIGHT.
> See ExecInitNestLoop().
>

Hmm, I see in match_unsorted_outer()
1254 case JOIN_RIGHT:
1255 case JOIN_FULL:
1256 nestjoinOK = false;
1257 useallclauses = true;
1258 break;

--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company