Support IS DISTINCT FROM expression

[MinhLA1410]

Currently, we already implement to support IS DISTINCT FROM expression like postgres_fdw for mysql_fdw. I would like to contribute them into repository and community. If you have interest? I will create pull request for share this feature.

Summary modification:

• Deparse IS NOT DISTINCT operator by <=> not equal operator.
• Refer: https://dev.mysql.com/doc/refman/8.0/en/comparison-operators.html#operator_equal-to

Reference testcase of postgres_fdw.sql in postgres_fdw:

EXPLAIN (VERBOSE, COSTS OFF)
  SELECT * FROM ft1 t1 WHERE (c1 IS NOT NULL) IS DISTINCT FROM (c7 IS NOT NULL);
                                                                               QUERY PLAN                                                                               
------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Foreign Scan on public.ft1 t1
   Output: c1, c2, c3, c4, c5, c6, c7, c8
   Local server startup cost: 10
   Remote query: SELECT `c1`, `c2`, `c3`, `c4`, `c5`, `c6`, `c7`, `c8` FROM `mysql_fdw_post`.`position_data1` WHERE ((NOT ((`c1` IS NOT NULL) <=> (`c7` IS NOT NULL))))
(4 rows)

[surajkharage19]

Thanks.

We have added IS DISTINCT FROM clause support in mysql_fdw after your request. Can you please check if that is useful for you and share your feedback? If you are happy with the latest addition, then can you please close the case from your end?

[jeevanchalke]

Committed the requested feature already. However, there is no feedback from the requester. So, closing the request.