OR clause on FLOAT/DOUBLE column unexpectedly evaluates to TRUE

[mrigger]

Consider the following statements:

CREATE TABLE t0(c0 FLOAT);
INSERT INTO t0(c0) VALUES (NULL);
SELECT * FROM t0 WHERE NOT(0 OR t0.c0); -- expected: {}, actual: {NULL}

Unexpectedly, the SELECT fetches a row. Since the predicate should evaluate to NULL, I would expect that no rows are fetched. When, for example, changing the type of c0 to INT, the query works as expected.

Environment:

mysql> select tidb_version();
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                                          |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v4.0.0-beta.2-160-g82529c886
Git Commit Hash: 82529c886cb1cfff7810476a136acf81284bac6e
Git Branch: master
UTC Build Time: 2020-04-01 11:44:27
GoVersion: go1.13.4
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

[Reminiscent]

Same with #15718 . This is because the keepNull variable in the isTrue expression signature was not pushed down. This can be fixed by #15926 .