ddl: fix reassigned partition id in truncate table does not take ef…

…fect (#7919)

fix reassigned partition id in truncate table does not take effect

ddl/db_test.go

@@ -3021,6 +3021,33 @@ func (s *testDBSuite) TestTruncatePartitionAndDropTable(c *C) {
 	hasOldPartitionData = checkPartitionDelRangeDone(c, s, partitionPrefix)
 	c.Assert(hasOldPartitionData, IsFalse)
 	s.testErrorCode(c, "select * from t4;", tmysql.ErrNoSuchTable)
+
+	// Test truncate table partition reassign a new partitionIDs.
+	s.tk.MustExec("drop table if exists t5;")
+	s.tk.MustExec("set @@session.tidb_enable_table_partition=1;")
+	s.tk.MustExec(`create table t5(
+		id int, name varchar(50), 
+		purchased date
+	)
+	partition by range( year(purchased) ) (
+    	partition p0 values less than (1990),
+    	partition p1 values less than (1995),
+    	partition p2 values less than (2000),
+    	partition p3 values less than (2005),
+    	partition p4 values less than (2010),
+    	partition p5 values less than (2015)
+   	);`)
+	is = domain.GetDomain(ctx).InfoSchema()
+	oldTblInfo, err = is.TableByName(model.NewCIStr("test"), model.NewCIStr("t5"))
+	c.Assert(err, IsNil)
+	oldPID = oldTblInfo.Meta().Partition.Definitions[0].ID
+
+	s.tk.MustExec("truncate table t5;")
+	is = domain.GetDomain(ctx).InfoSchema()
+	c.Assert(err, IsNil)
+	newTblInfo, err := is.TableByName(model.NewCIStr("test"), model.NewCIStr("t5"))
+	newPID := newTblInfo.Meta().Partition.Definitions[0].ID
+	c.Assert(oldPID != newPID, IsTrue)
 }
 
 func (s *testDBSuite) TestPartitionUniqueKeyNeedAllFieldsInPf(c *C) {

ddl/partition.go

@@ -417,3 +417,24 @@ func isRangePartitionColUnsignedBigint(cols []*table.Column, pi *model.Partition
 	}
 	return false
 }
+
+// truncateTableByReassignPartitionIDs reassign a new partition ids.
+func truncateTableByReassignPartitionIDs(job *model.Job, t *meta.Meta, tblInfo *model.TableInfo) error {
+	newDefs := make([]model.PartitionDefinition, 0, len(tblInfo.Partition.Definitions))
+	for _, def := range tblInfo.Partition.Definitions {
+		pid, err := t.GenGlobalID()
+		if err != nil {
+			job.State = model.JobStateCancelled
+			return errors.Trace(err)
+		}
+		newDef := model.PartitionDefinition{
+			ID:       pid,
+			Name:     def.Name,
+			LessThan: def.LessThan,
+			Comment:  def.Comment,
+		}
+		newDefs = append(newDefs, newDef)
+	}
+	tblInfo.Partition.Definitions = newDefs
+	return nil
+}

ddl/table.go

@@ -209,18 +209,13 @@ func onTruncateTable(d *ddlCtx, t *meta.Meta, job *model.Job) (ver int64, _ erro
 		return ver, errors.Trace(err)
 	}
 
-	// We use the new partition ID because all the old data is encoded with the old partition ID, it can not be accessed anymore.
 	var oldPartitionIDs []int64
 	if tblInfo.GetPartitionInfo() != nil {
 		oldPartitionIDs = getPartitionIDs(tblInfo)
-		for _, def := range tblInfo.Partition.Definitions {
-			var pid int64
-			pid, err = t.GenGlobalID()
-			if err != nil {
-				job.State = model.JobStateCancelled
-				return ver, errors.Trace(err)
-			}
-			def.ID = pid
+		// We use the new partition ID because all the old data is encoded with the old partition ID, it can not be accessed anymore.
+		err = truncateTableByReassignPartitionIDs(job, t, tblInfo)
+		if err != nil {
+			return ver, errors.Trace(err)
 		}
 	}