"Qu, Mischa, Majorel China" <mischa(dot)qu(at)majorel(dot)cn> writes:
> But when I run some full table scans and found a problems. the results of the following sql were different.
> Method 1: directly join external table and local table
> select count(distinct user_id),count(distinct member_code)
> from a_fdw t1
> join b as t6 on t1.user_id=t6.tags ->> '10'::varchar(50)
> where coalesce(user_id,'') <> '';
> -- result: 50739 50845
What sort of plan is that query using? If it's a merge join, I'd
bet that the problem is related to local and remote servers not
having the same default collation.
regards, tom lane