MySQL Bugs: #120510: A false DECIMAL equality wrongly returns a row in the original path

Bug #120510	A false DECIMAL equality wrongly returns a row in the original path
Submitted:	21 May 7:22	Modified:	21 May 11:50
Reporter:	y x	Email Updates:
Status:	Can't repeat	Impact on me:	None
Category:	MySQL Server	Severity:	S3 (Non-critical)
Version:	9.6.0	OS:	Ubuntu
Assigned to:		CPU Architecture:	x86

Description:
`t1.c0` and `t2.c0` are scale-0 `DECIMAL` columns, so inserting the two non-integer literals stores both as `0`; the final filter `t2.c0 = 0.019732417266349445` should therefore be false, but in the original path MySQL incorrectly treats it as true after combining it with the other always-true DECIMAL predicates.

How to repeat:
CREATE TABLE t1(c0 DECIMAL);
CREATE TABLE t2(c0 DECIMAL);

INSERT INTO t1 VALUES(0.167019786236149);
INSERT INTO t2 VALUES(0.12736447690010488);

SELECT t2.c0 AS ref0
FROM t1
INNER JOIN t2
    ON ((t1.c0) = (t2.c0))
    && ((((((((t2.c0) IS NOT NULL) AND ((t2.c0) > (IFNULL((+ (4.47373999E8)), 1861378397))))
        || ((t2.c0) NOT IN ((+ (0.14355415844276698)))))
        OR ((t2.c0) NOT IN ((+ (t2.c0)))))
        && ((IFNULL(t2.c0, IFNULL(t2.c0, t2.c0))) IN (-1234616201, -496856630, t2.c0, t2.c0, (+ (-296021719)))))
        OR ((t2.c0) IN (t2.c0)))
        AND ((t2.c0) BETWEEN ((+ (t2.c0))) AND (t2.c0)))
WHERE ((t1.c0) LIKE (t2.c0))
  AND ((t2.c0) = (0.019732417266349445)); -- Expected correct result: <empty>  -- actual Wrong result: 0

Thank you for the bug report.

However, on both our supported versions, 8.4 and 9.7, I get the expected result, an empty result set.

Thank you for checking.

On my local instance, `SELECT VERSION()` returns `9.6.0`.

If this no longer reproduces on 8.4 and 9.7, then it may already be fixed there. Could you please confirm whether this was fixed between 9.6 and 9.7?