MDEV-40088 [to-squash] Disallow subqueries in INTERVAL clause in range interval auto partitioning

This is consistent with system time (versioning) partitioning. Also
consistent is that both allow expressions otherwise.

Author: mariadb-YuchenPei

mysql-test/main/partition_range_interval.result

@@ -2473,3 +2473,50 @@ t1	CREATE TABLE `t1` (
  PARTITION `p6` VALUES LESS THAN ('2026-04-26') ENGINE = InnoDB)
 DROP TABLE t1, t2;
 drop function f;
+#
+# MDEV-40088 Assertion `fixed()' failed with INTERVAL (SELECT 1) DAY
+#
+# Existing error should remain the same
+create table t1 (c date) engine=innodb
+PARTITION BY RANGE COLUMNS (c)
+(
+PARTITION p0 VALUES LESS THAN ((select '2026-04-20'))
+);
+ERROR HY000: This partition function is not allowed
+create table t1 (c date) engine=innodb
+PARTITION BY RANGE COLUMNS (c)
+INTERVAL (SELECT 1) DAY
+(
+PARTITION p0 VALUES LESS THAN ('2026-04-20')
+);
+ERROR 42000: INTERVAL does not support subqueries or stored functions
+create table t1 (c date) engine=innodb
+PARTITION BY RANGE COLUMNS (c)
+INTERVAL (1 + 2 + 3) DAY
+(
+PARTITION p0 VALUES LESS THAN ('2026-04-20')
+);
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `c` date DEFAULT NULL
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
+ PARTITION BY RANGE  COLUMNS(`c`) INTERVAL 6 DAY
+(PARTITION `p0` VALUES LESS THAN ('2026-04-20') ENGINE = InnoDB)
+drop table t1;
+# Existing error should remain the same, even if subquries are
+# banned for INTERVAL
+create table t1 (c date) engine=innodb
+PARTITION BY RANGE COLUMNS (c)
+INTERVAL 1 DAY
+(
+PARTITION p0 VALUES LESS THAN ((select '2026-04-20'))
+);
+ERROR HY000: This partition function is not allowed
+create table t1 (c date) engine=innodb
+PARTITION BY RANGE COLUMNS (c)
+INTERVAL "hello" DAY
+(
+PARTITION p0 VALUES LESS THAN ('2026-04-20')
+);
+ERROR HY000: Wrong parameters for partitioned `t1`: wrong value for 'INTERVAL'

mysql-test/main/partition_range_interval.test

@@ -958,3 +958,50 @@ SHOW CREATE TABLE t1;
 DROP TABLE t1, t2;
 drop function f;
 
+--echo #
+--echo # MDEV-40088 Assertion `fixed()' failed with INTERVAL (SELECT 1) DAY
+--echo #
+
+--echo # Existing error should remain the same
+--error ER_PARTITION_FUNCTION_IS_NOT_ALLOWED
+create table t1 (c date) engine=innodb
+PARTITION BY RANGE COLUMNS (c)
+(
+PARTITION p0 VALUES LESS THAN ((select '2026-04-20'))
+);
+
+--error ER_SUBQUERIES_NOT_SUPPORTED
+create table t1 (c date) engine=innodb
+PARTITION BY RANGE COLUMNS (c)
+INTERVAL (SELECT 1) DAY
+(
+PARTITION p0 VALUES LESS THAN ('2026-04-20')
+);
+
+create table t1 (c date) engine=innodb
+PARTITION BY RANGE COLUMNS (c)
+INTERVAL (1 + 2 + 3) DAY
+(
+PARTITION p0 VALUES LESS THAN ('2026-04-20')
+);
+
+show create table t1;
+drop table t1;
+
+--echo # Existing error should remain the same, even if subquries are
+--echo # banned for INTERVAL
+--error ER_PARTITION_FUNCTION_IS_NOT_ALLOWED
+create table t1 (c date) engine=innodb
+PARTITION BY RANGE COLUMNS (c)
+INTERVAL 1 DAY
+(
+PARTITION p0 VALUES LESS THAN ((select '2026-04-20'))
+);
+
+--error ER_PART_WRONG_VALUE
+create table t1 (c date) engine=innodb
+PARTITION BY RANGE COLUMNS (c)
+INTERVAL "hello" DAY
+(
+PARTITION p0 VALUES LESS THAN ('2026-04-20')
+);

sql/sql_partition_auto_interval.cc

@@ -391,6 +391,8 @@ bool partition_info::set_range_interval(THD* thd, Item* ival,
                                         interval_type type,
                                         const char *table_name)
 {
+  if (ival->fix_fields_if_needed_for_scalar(thd, &ival))
+    return true;
   bool error= get_interval_value(thd, ival, type, &interval) ||
     interval.neg || interval.second_part ||
     !(interval.year || interval.month || interval.day || interval.hour ||

sql/sql_yacc.yy

@@ -5199,7 +5199,13 @@ part_column_list:
 
 opt_part_interval:
           /* empty */ {}
-        | INTERVAL_SYM expr interval opt_auto
+        | { Lex->clause_that_disallows_subselect= "INTERVAL"; }
+          opt_part_interval2
+          { Lex->clause_that_disallows_subselect= NULL; }
+        ;
+
+opt_part_interval2:
+          INTERVAL_SYM expr interval opt_auto
           {
             partition_info *part_info= Lex->part_info;
             const char *table_name=