Fix for BUG#18025: Wrong query results because of bugs in partition pruning:

 - Fix typo bug in SEL_ARG::is_singlepoint()
 - In set_up_range_analysis_info(), treat MEDIUMINT as enumerable type just like other integer types

mysql-test/r/partition_pruning.result

@@ -545,3 +545,41 @@ show status like 'Handler_read_next';
 Variable_name	Value
 Handler_read_next	0
 drop table t1, t2;
+create table t1 ( f_int1 mediumint, f_int2 integer) 
+partition by list(mod(f_int1,4)) (
+partition p_3 values in (-3),
+partition p_2 values in (-2),
+partition p_1 values in (-1),
+partition p0 values in (0),
+partition p1 values in (1),
+partition p2 values in (2),
+partition p3 values in (3)
+);
+insert into t1 values (9, 9), (8, 8), (7, 7), (6, 6), (5, 5), 
+(4, 4), (3, 3), (2, 2), (1, 1);
+select * from t1 where f_int1 between 5 and 15 order by f_int1;
+f_int1	f_int2
+5	5
+6	6
+7	7
+8	8
+9	9
+drop table t1;
+create table t1 (a char(10)) partition by list(length(a)) (
+partition p1 values in (1),
+partition p2 values in (2),
+partition p3 values in (3),
+partition p4 values in (4),
+partition p5 values in (5)
+);
+insert into t1 values ('a'),('bb'),('ccc'),('dddd'),('eeEee');
+select * from t1 where a>='a' and a <= 'dddd';
+a
+a
+bb
+ccc
+dddd
+explain partitions select * from t1 where a>='a' and a <= 'dddd';
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	p1,p2,p3,p4,p5	ALL	NULL	NULL	NULL	NULL	5	Using where
+drop table t1;

mysql-test/t/partition_pruning.test

@@ -447,5 +447,37 @@ show status like 'Handler_read_next';
 
 drop table t1, t2;
 
+# BUG#18025 
+#  part1: mediumint columns
+create table t1 ( f_int1 mediumint, f_int2 integer) 
+partition by list(mod(f_int1,4)) (
+  partition p_3 values in (-3),
+  partition p_2 values in (-2),
+  partition p_1 values in (-1),
+  partition p0 values in (0),
+  partition p1 values in (1),
+  partition p2 values in (2),
+  partition p3 values in (3)
+);
+
+insert into t1 values (9, 9), (8, 8), (7, 7), (6, 6), (5, 5), 
+                      (4, 4), (3, 3), (2, 2), (1, 1);
+select * from t1 where f_int1 between 5 and 15 order by f_int1;
+
+drop table t1;
+
+#  part2: bug in pruning code
+create table t1 (a char(10)) partition by list(length(a)) (
+  partition p1 values in (1),
+  partition p2 values in (2),
+  partition p3 values in (3),
+  partition p4 values in (4),
+  partition p5 values in (5)
+);
+insert into t1 values ('a'),('bb'),('ccc'),('dddd'),('eeEee');
+select * from t1 where a>='a' and a <= 'dddd';
+explain partitions select * from t1 where a>='a' and a <= 'dddd';
+drop table t1;
+
 # No tests for NULLs in RANGE(monotonic_expr()) - they depend on BUG#15447
 # being fixed.

sql/opt_range.cc

@@ -339,7 +339,7 @@ public:
     if (min_flag || max_flag)
       return FALSE;
     byte *min_val= (byte *)min_value;
-    byte *max_val= (byte *)min_value;
+    byte *max_val= (byte *)max_value;
 
     if (maybe_null)
     {

sql/sql_partition.cc

@@ -5643,6 +5643,7 @@ static void set_up_range_analysis_info(partition_info *part_info)
     switch (field->type()) {
     case MYSQL_TYPE_TINY:
     case MYSQL_TYPE_SHORT:
+    case MYSQL_TYPE_INT24:
     case MYSQL_TYPE_LONG:
     case MYSQL_TYPE_LONGLONG:
       part_info->get_part_iter_for_interval=