ddl: support the rolling upgrade. (pingcap#6301)

ddl/column.go

@@ -450,6 +450,13 @@ func (d *ddl) doModifyColumn(t *meta.Meta, job *model.Job, newCol *model.ColumnI
  return ver, infoschema.ErrColumnNotExists.GenByArgs(oldName, tblInfo.Name)
  }
 
+ // gofail: var uninitializedOffsetAndState bool
+ // if uninitializedOffsetAndState {
+ // if newCol.State != model.StatePublic {
+ // return ver, errors.New("the column state is wrong")
+ // }
+ // }
+
  // We need the latest column's offset and state. This information can be obtained from the store.
  newCol.Offset = oldCol.Offset
  newCol.State = oldCol.State

ddl/ddl_api.go

@@ -1259,7 +1259,16 @@ func (d *ddl) getModifiableColumnJob(ctx context.Context, ident ast.Ident, origi
  }
 
  newCol := table.ToColumn(&model.ColumnInfo{
- ID: col.ID,
+ ID: col.ID,
+ // We use this PR(https://github.com/pingcap/tidb/pull/6274) as the dividing line to define whether it is a new version or an old version TiDB.
+ // The old version TiDB initializes the column's offset and state here.
+ // The new version TiDB doesn't initialize the column's offset and state, and it will do the initialization in run DDL function.
+ // When we do the rolling upgrade the following may happen:
+ // a new version TiDB builds the DDL job that doesn't be set the column's offset and state,
+ // and the old version TiDB is the DDL owner, it doesn't get offset and state from the store. Then it will encounter errors.
+ // So here we set offset and state to support the rolling upgrade.
+ Offset: col.Offset,
+ State: col.State,
  OriginDefaultValue: col.OriginDefaultValue,
  FieldType: *spec.NewColumn.Tp,
  Name: spec.NewColumn.Name.Name,

ddl/fail_db_test.go

@@ -0,0 +1,35 @@
+// Copyright 2018 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ddl_test
+
+import (
+ gofail "github.com/coreos/gofail/runtime"
+ . "github.com/pingcap/check"
+ "golang.org/x/net/context"
+)
+
+// TestInitializeOffsetAndState tests the case that the column's offset and state don't be initialized in the file of ddl_api.go when
+// doing the operation of 'modify column'.
+func (s *testStateChangeSuite) TestInitializeOffsetAndState(c *C) {
+ _, err := s.se.Execute(context.Background(), "use test_db_state")
+ c.Assert(err, IsNil)
+ _, err = s.se.Execute(context.Background(), "create table t(a int, b int, c int)")
+ c.Assert(err, IsNil)
+ defer s.se.Execute(context.Background(), "drop table t")
+
+ gofail.Enable("github.com/pingcap/tidb/ddl/uninitializedOffsetAndState", `return(true)`)
+ _, err = s.se.Execute(context.Background(), "ALTER TABLE t MODIFY COLUMN b int FIRST;")
+ c.Assert(err, IsNil)
+ gofail.Disable("github.com/pingcap/tidb/ddl/uninitializedOffsetAndState")
+}