Incorrect query result

[sayJason]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

CREATE TABLE t1 (c1 INT);
INSERT INTO t1 VALUES (1);
SELECT c1 FROM t1 WHERE c1 REGEXP(IFNULL(c1, 0.0)); -- actual: {1}, expected: {}

2. What did you expect to see? (Required)

SELECT returns nothing.

3. What did you see instead (Required)

SELECT returns 1.

4. What is your TiDB version? (Required)

Release Version: v7.0.0
Edition: Community
Git Commit Hash: 7376954
Git Branch: heads/refs/tags/v7.0.0
UTC Build Time: 2023-03-29 13:32:13
GoVersion: go1.20.2
Race Enabled: false
TiKV Min Version: 6.2.0-alpha
Check Table Before Drop: false
Store: tikv

[bb7133]

@jebter I believe the root cause is about the expression evaluation of REGEXP(IFNULL(c1, 0.0));, reassign it to "sig/execution".

[SeaRise]

/assign @SeaRise

[SeaRise]

use test;
CREATE TABLE t1 (c1 INT);
INSERT INTO t1 VALUES (1);

## mysql
SELECT concat(IFNULL(c1, 0.0)) from t1;
+-----------------------------+
| concat(IFNULL(c1, 0.0), '') |
+-----------------------------+
| 1.0                         |
+-----------------------------+

SELECT concat(IFNULL(c1, 0)) from t1;
+---------------------------+
| concat(IFNULL(c1, 0), '') |
+---------------------------+
| 1                         |
+---------------------------+

## tidb
SELECT concat(IFNULL(c1, 0.0)) from t1;
+-----------------------------+
| concat(IFNULL(c1, 0.0), '') |
+-----------------------------+
| 1                           |
+-----------------------------+

SELECT concat(IFNULL(c1, 0)) from t1;
+---------------------------+
| concat(IFNULL(c1, 0), '') |
+---------------------------+
| 1                         |
+---------------------------+

The difference is the result of casting a decimal as a string.