Re: psql12.3 + jdbc_fdw - return wrong query results by using OR

On 5/28/20 8:39 AM, emilu(at)encs(dot)concordia(dot)ca wrote:
> Hello,
>
> psql12.3 + jdbc_fdw(oracle18.x), tried:
>
> [1]
> select count(*)
> from oracle_t1 as a
> inner join local_t1 as b
> on (a.c1 = b.c1);
>
> return 100 records
>
> [2]
> select count(*)
> from oracle_t1 as a
> inner join local_t1 as b
> on (a.c1 = b.c1
>     OR
>     a.c2 = b.c1
>    );
>
> return only 2 records
>
> (no null values in both tables.)
>
> May I know what may cause the error please?

I'm guessing you are seeing this:

https://www.postgresql.org/docs/12/sql-expressions.html

4.2.14. Expression Evaluation Rules

". Boolean expressions (AND/OR/NOT combinations) in those clauses can be
reorganized in any manner allowed by the laws of Boolean algebra."

It would help to see the EXPLAIN ANALYZE for the queries above.

>
> Thanks a lot.
>
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com