ddl: increasing value of partition by range columns fix (#32748) (#33643)

close pingcap/tidb#32748

ddl/db_partition_test.go

@@ -545,6 +545,13 @@ create table log_message_1 (
 				"partition p1 values less than ('G'));",
 			dbterror.ErrRangeNotIncreasing,
 		},
+		{
+			"create table t(a char(10) collate utf8mb4_bin) " +
+				"partition by range columns (a) (" +
+				"partition p0 values less than ('g'), " +
+				"partition p1 values less than ('A'));",
+			dbterror.ErrRangeNotIncreasing,
+		},
 		{
 			"CREATE TABLE t1(c0 INT) PARTITION BY HASH((NOT c0)) PARTITIONS 2;",
 			dbterror.ErrPartitionFunctionIsNotAllowed,
@@ -617,6 +624,14 @@ create table log_message_1 (
     	partition p0 values less than ('a'),
     	partition p1 values less than ('G'));`)
 
+	tk.MustExec("drop table if exists t;")
+	tk.MustExec(`create table t (a varchar(255) charset utf8mb4 collate utf8mb4_bin) ` +
+		`partition by range columns (a) ` +
+		`(partition pnull values less than (""),` +
+		`partition puppera values less than ("AAA"),` +
+		`partition plowera values less than ("aaa"),` +
+		`partition pmax values less than (MAXVALUE))`)
+
 	tk.MustExec("drop table if exists t;")
 	tk.MustExec(`create table t(a int) partition by range columns (a) (
     	partition p0 values less than (10),

ddl/ddl_api.go

@@ -2681,11 +2681,6 @@ func checkTwoRangeColumns(ctx sessionctx.Context, curr, prev *model.PartitionDef
 			return false, nil
 		}
 
-		// Current and previous is the same.
-		if strings.EqualFold(curr.LessThan[i], prev.LessThan[i]) {
-			continue
-		}
-
 		// The tuples of column values used to define the partitions are strictly increasing:
 		// PARTITION p0 VALUES LESS THAN (5,10,'ggg')
 		// PARTITION p1 VALUES LESS THAN (10,20,'mmm')