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…query NOT IN can return a row that should be excluded when a materialized subquery contains NULL and the outer value cannot be represented by the subquery's index key type. For example, outer INT value 9999 compared with a TINYINT subquery containing 21 and NULL must not pass the predicate. A failed conversion of the outer value into an exact-lookup key immediately returns FALSE for IN. This bypasses the NULL-aware partial-match phase, although failure of an exact lookup does not rule out an UNKNOWN result caused by NULL in the subquery. Skip the exact index lookup when key conversion fails. Continue through the existing NULL-aware partial-match handling instead of returning FALSE early. Preserve successful exact lookups and the materialized-subquery execution strategy. The regression compares INT values, including 9999, with a materialized TINYINT subquery containing NULL and expects no rows from NOT IN. Bug report: https://jira.mariadb.org/browse/MDEV-40877
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NOT IN can return a row that should be excluded when a materialized subquery contains NULL and the outer value cannot be represented by the subquery's index key type. For example, outer INT value 9999 compared with a TINYINT subquery containing 21 and NULL must not pass the predicate.
Bug report: https://jira.mariadb.org/browse/MDEV-40877
Root cause
A failed conversion of the outer value into an exact-lookup key immediately returns FALSE for IN. This bypasses the NULL-aware partial-match phase, although failure of an exact lookup does not rule out an UNKNOWN result caused by NULL in the subquery.
Changes
Regression coverage
The regression compares INT values, including 9999, with a materialized TINYINT subquery containing NULL and expects no rows from NOT IN.
mysql-test/main/not_in_materialized_null.resultmysql-test/main/not_in_materialized_null.testValidation
On
11.4atd10e5d726799b1cd57cc866f40aad68c720803da:main.not_in_materialized_nullfailed on the unchanged target branch and passed with this fix.main.select,main.subselect.