ddl: fix a bug that adding range partition meets error when value is …

…negative (pingcap#11407)

ddl/db_partition_test.go

@@ -495,6 +495,19 @@ func (s *testIntegrationSuite5) TestAlterTableAddPartition(c *C) {
 		partition p5 values less than maxvalue
 	);`
 	assertErrorCode(c, tk, sql7, tmysql.ErrSameNamePartition)
+
+	tk.MustExec("alter table table3 add partition (partition p3 values less than (2001 + 10))")
+
+	// less than value can be negative or expression.
+	tk.MustExec(`CREATE TABLE tt5 (
+		c3 bigint(20) NOT NULL
+	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
+	PARTITION BY RANGE ( c3 ) (
+		PARTITION p0 VALUES LESS THAN (-3),
+		PARTITION p1 VALUES LESS THAN (-2)
+	);`)
+	tk.MustExec(`ALTER TABLE tt5 add partition ( partition p2 values less than (-1) );`)
+	tk.MustExec(`ALTER TABLE tt5 add partition ( partition p3 values less than (5-1) );`)
 }
 
 func (s *testIntegrationSuite6) TestAlterTableDropPartition(c *C) {
@@ -1436,6 +1449,9 @@ func (s *testIntegrationSuite4) TestPartitionErrorCode(c *C) {
 	_, err := tk.Exec("alter table employees add partition partitions 8;")
 	c.Assert(ddl.ErrUnsupportedAddPartition.Equal(err), IsTrue)
 
+	_, err = tk.Exec("alter table employees add partition (partition p5 values less than (42));")
+	c.Assert(ddl.ErrUnsupportedAddPartition.Equal(err), IsTrue)
+
 	// coalesce partition
 	tk.MustExec(`create table clients (
 		id int,

ddl/ddl_api.go

@@ -2114,7 +2114,8 @@ func (d *ddl) AddTablePartitions(ctx sessionctx.Context, ident ast.Ident, spec *
 	}
 
 	meta := t.Meta()
-	if meta.GetPartitionInfo() == nil {
+	pi := meta.GetPartitionInfo()
+	if pi == nil {
 		return errors.Trace(ErrPartitionMgmtOnNonpartitioned)
 	}
 	// We don't support add hash type partition now.
@@ -2137,7 +2138,11 @@ func (d *ddl) AddTablePartitions(ctx sessionctx.Context, ident ast.Ident, spec *
 		return errors.Trace(err)
 	}
 
-	err = checkAddPartitionValue(meta, partInfo)
+	// partInfo contains only the new added partition, we have to combine it with the
+	// old partitions to check all partitions is strictly increasing.
+	tmp := *partInfo
+	tmp.Definitions = append(pi.Definitions, tmp.Definitions...)
+	err = checkCreatePartitionValue(ctx, meta, &tmp, t.Cols())
 	if err != nil {
 		return errors.Trace(err)
 	}
@@ -3270,27 +3275,12 @@ func buildPartitionInfo(meta *model.TableInfo, d *ddl, spec *ast.AlterTableSpec)
 		Columns: meta.Partition.Columns,
 		Enable:  meta.Partition.Enable,
 	}
+
 	genIDs, err := d.genGlobalIDs(len(spec.PartDefinitions))
 	if err != nil {
 		return nil, err
 	}
-	buf := new(bytes.Buffer)
 	for ith, def := range spec.PartDefinitions {
-		for _, expr := range def.LessThan {
-			tp := expr.GetType().Tp
-			if len(part.Columns) == 0 {
-				// Partition by range.
-				if !(tp == mysql.TypeLong || tp == mysql.TypeLonglong) {
-					expr.Format(buf)
-					if strings.EqualFold(buf.String(), "MAXVALUE") {
-						continue
-					}
-					buf.Reset()
-					return nil, infoschema.ErrColumnNotExists.GenWithStackByArgs(buf.String(), "partition function")
-				}
-			}
-			// Partition by range columns if len(part.Columns) != 0.
-		}
 		piDef := model.PartitionDefinition{
 			Name:    def.Name,
 			ID:      genIDs[ith],