With (c0, vp_rowid) index ref access, string '0.45' is wrongly converted to integer key 0, causing multi-table reconstructed query to return c0=0 rows while single-table returns 0 rows.

1. 1. 1. Problem Description
         When the condition `'0.45' IN (c0)` uses the `(c0, vp_rowid)` index for `ref` access, MariaDB incorrectly converts the string value `'0.45'` to the integer index key `0`, thereby matching rows with `c0=0`. A full table scan returns 0 rows according to correct numeric comparison semantics. This produces inconsistent results between the single-table query and the multi-table LEFT JOIN derived-table reconstructed query.

1. 1. 1. How to Reproduce
         Execute the following SQL:

```sql
DROP DATABASE IF EXISTS repro_mariadb808_db12_min;
CREATE DATABASE repro_mariadb808_db12_min;
USE repro_mariadb808_db12_min;

CREATE TABLE source_rows (
vp_rowid BIGINT NOT NULL PRIMARY KEY,
c0 TINYINT(1),
c1 CHAR(1) NOT NULL,
KEY idx_source (vp_rowid, c0)
);

CREATE TABLE left_rows (
vp_rowid BIGINT NOT NULL PRIMARY KEY,
c0 TINYINT(1),
KEY idx_left (c0, vp_rowid)
);

CREATE TABLE right_rows (
vp_rowid BIGINT NOT NULL PRIMARY KEY,
c1 CHAR(1) NOT NULL
);

INSERT INTO source_rows VALUES
(1, 0, 'a'),
(2, 0, 'b'),
(3, 1, 'c');

INSERT INTO left_rows
SELECT vp_rowid, c0 FROM source_rows;

INSERT INTO right_rows
SELECT vp_rowid, c1 FROM source_rows;

– Original single-table query: actually returns 0 rows
SELECT vp_rowid, c0
FROM source_rows
WHERE '0.45' IN (c0);

– VP multi-table reconstructed query: incorrectly returns two rows with c0=0
SELECT vp_rowid, c0
FROM (
SELECT l.vp_rowid, l.c0, r.c1
FROM left_rows AS l
LEFT JOIN right_rows AS r
ON r.vp_rowid = l.vp_rowid
) AS reconstructed
WHERE '0.45' IN (c0);
```

1. 1. 1. Expected Behavior
         The single-table query and the multi-table reconstructed query should return identical results, i.e., 0 rows each.

1. 1. 1. Actual Behavior

• Single-table query: returns 0 rows (Empty set).
• Multi-table reconstructed query: incorrectly returns two rows with `c0=0`.

1. 1. 1. Additional Verification
         Disabling the problematic index:
         ```sql
         SELECT vp_rowid, c0
         FROM left_rows IGNORE INDEX (idx_left)
         WHERE '0.45' IN (c0);
         ```
         The result correctly returns 0 rows, and the execution plan becomes:
         ```
         table type key rows Extra
         left_rows ALL NULL 3 Using where; Using temporary
         ```

Therefore, the problem is clear: when using the `(c0, vp_rowid)` index for `ref` access, MariaDB incorrectly converts the string value `'0.45'` to the integer index key `0`, thereby matching `c0=0`; a full table scan returns 0 rows according to correct numeric comparison semantics.