ddl: fix unexpect fail when create expression index

ddl/backfilling.go

@@ -626,8 +626,7 @@ func loadDDLReorgVars(ctx context.Context, sessPool *sessionPool) error {
 	return ddlutil.LoadDDLReorgVars(ctx, sCtx)
 }
 
-func makeupDecodeColMap(sessCtx sessionctx.Context, t table.Table) (map[int64]decoder.Column, error) {
-	dbName := model.NewCIStr(sessCtx.GetSessionVars().CurrentDB)
+func makeupDecodeColMap(sessCtx sessionctx.Context, dbName model.CIStr, t table.Table) (map[int64]decoder.Column, error) {
 	writableColInfos := make([]*model.ColumnInfo, 0, len(t.WritableCols()))
 	for _, col := range t.WritableCols() {
 		writableColInfos = append(writableColInfos, col.ColumnInfo)
@@ -860,7 +859,7 @@ func (dc *ddlCtx) writePhysicalTableRecord(sessPool *sessionPool, t table.Physic
 
 	startKey, endKey := reorgInfo.StartKey, reorgInfo.EndKey
 	sessCtx := newContext(reorgInfo.d.store)
-	decodeColMap, err := makeupDecodeColMap(sessCtx, t)
+	decodeColMap, err := makeupDecodeColMap(sessCtx, reorgInfo.dbInfo.Name, t)
 	if err != nil {
 		return errors.Trace(err)
 	}

ddl/column.go

@@ -807,7 +807,11 @@ func doReorgWorkForModifyColumn(w *worker, d *ddlCtx, t *meta.Meta, job *model.J
 	oldCol, changingCol *model.ColumnInfo, changingIdxs []*model.IndexInfo) (done bool, ver int64, err error) {
 	job.ReorgMeta.ReorgTp = model.ReorgTypeTxn
 	rh := newReorgHandler(t, w.sess, w.concurrentDDL)
-	reorgInfo, err := getReorgInfo(d.jobContext(job), d, rh, job, tbl, BuildElements(changingCol, changingIdxs), false)
+	dbInfo, err := t.GetDatabase(job.SchemaID)
+	if err != nil {
+		return false, ver, errors.Trace(err)
+	}
+	reorgInfo, err := getReorgInfo(d.jobContext(job), d, rh, job, dbInfo, tbl, BuildElements(changingCol, changingIdxs), false)
 	if err != nil || reorgInfo.first {
 		// If we run reorg firstly, we should update the job snapshot version
 		// and then run the reorg next time.

ddl/db_change_test.go

@@ -1712,6 +1712,14 @@ func TestCreateExpressionIndex(t *testing.T) {
 	require.NoError(t, checkErr)
 	tk.MustExec("admin check table t")
 	tk.MustQuery("select * from t order by a, b").Check(testkit.Rows("0 9", "0 11", "0 11", "1 7", "2 7", "5 7", "8 8", "10 10", "10 10"))
+
+	// https://github.com/pingcap/tidb/issues/39784
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(name varchar(20))")
+	tk.MustExec("insert into t values ('Abc'), ('Bcd'), ('abc')")
+	tk.MustExec("create index idx on test.t((lower(test.t.name)))")
+	tk.MustExec("admin check table t")
 }
 
 func TestCreateUniqueExpressionIndex(t *testing.T) {

ddl/index.go

@@ -870,7 +870,11 @@ func runReorgJobAndHandleErr(w *worker, d *ddlCtx, t *meta.Meta, job *model.Job,
 	tbl table.Table, indexInfo *model.IndexInfo, mergingTmpIdx bool) (done bool, ver int64, err error) {
 	elements := []*meta.Element{{ID: indexInfo.ID, TypeKey: meta.IndexElementKey}}
 	rh := newReorgHandler(t, w.sess, w.concurrentDDL)
-	reorgInfo, err := getReorgInfo(d.jobContext(job), d, rh, job, tbl, elements, mergingTmpIdx)
+	dbInfo, err := t.GetDatabase(job.SchemaID)
+	if err != nil {
+		return false, ver, errors.Trace(err)
+	}
+	reorgInfo, err := getReorgInfo(d.jobContext(job), d, rh, job, dbInfo, tbl, elements, mergingTmpIdx)
 	if err != nil || reorgInfo.first {
 		// If we run reorg firstly, we should update the job snapshot version
 		// and then run the reorg next time.

ddl/partition.go

@@ -1743,6 +1743,10 @@ func (w *worker) onDropTablePartition(d *ddlCtx, t *meta.Meta, job *model.Job) (
 		if err != nil {
 			return ver, errors.Trace(err)
 		}
+		dbInfo, err := t.GetDatabase(job.SchemaID)
+		if err != nil {
+			return ver, errors.Trace(err)
+		}
 		// If table has global indexes, we need reorg to clean up them.
 		if pt, ok := tbl.(table.PartitionedTable); ok && hasGlobalIndex(tblInfo) {
 			// Build elements for compatible with modify column type. elements will not be used when reorganizing.
@@ -1753,7 +1757,7 @@ func (w *worker) onDropTablePartition(d *ddlCtx, t *meta.Meta, job *model.Job) (
 				}
 			}
 			rh := newReorgHandler(t, w.sess, w.concurrentDDL)
-			reorgInfo, err := getReorgInfoFromPartitions(d.jobContext(job), d, rh, job, tbl, physicalTableIDs, elements)
+			reorgInfo, err := getReorgInfoFromPartitions(d.jobContext(job), d, rh, job, dbInfo, tbl, physicalTableIDs, elements)
 
 			if err != nil || reorgInfo.first {
 				// If we run reorg firstly, we should update the job snapshot version

ddl/reorg.go

@@ -386,6 +386,7 @@ type reorgInfo struct {
 	// PhysicalTableID is used to trace the current partition we are handling.
 	// If the table is not partitioned, PhysicalTableID would be TableID.
 	PhysicalTableID int64
+	dbInfo          *model.DBInfo
 	elements        []*meta.Element
 	currElement     *meta.Element
 }
@@ -585,7 +586,7 @@ func getValidCurrentVersion(store kv.Storage) (ver kv.Version, err error) {
 	return ver, nil
 }
 
-func getReorgInfo(ctx *JobContext, d *ddlCtx, rh *reorgHandler, job *model.Job,
+func getReorgInfo(ctx *JobContext, d *ddlCtx, rh *reorgHandler, job *model.Job, dbInfo *model.DBInfo,
 	tbl table.Table, elements []*meta.Element, mergingTmpIdx bool) (*reorgInfo, error) {
 	var (
 		element *meta.Element
@@ -685,11 +686,12 @@ func getReorgInfo(ctx *JobContext, d *ddlCtx, rh *reorgHandler, job *model.Job,
 	info.currElement = element
 	info.elements = elements
 	info.mergingTmpIdx = mergingTmpIdx
+	info.dbInfo = dbInfo
 
 	return &info, nil
 }
 
-func getReorgInfoFromPartitions(ctx *JobContext, d *ddlCtx, rh *reorgHandler, job *model.Job, tbl table.Table, partitionIDs []int64, elements []*meta.Element) (*reorgInfo, error) {
+func getReorgInfoFromPartitions(ctx *JobContext, d *ddlCtx, rh *reorgHandler, job *model.Job, dbInfo *model.DBInfo, tbl table.Table, partitionIDs []int64, elements []*meta.Element) (*reorgInfo, error) {
 	var (
 		element *meta.Element
 		start   kv.Key
@@ -745,6 +747,7 @@ func getReorgInfoFromPartitions(ctx *JobContext, d *ddlCtx, rh *reorgHandler, jo
 	info.PhysicalTableID = pid
 	info.currElement = element
 	info.elements = elements
+	info.dbInfo = dbInfo
 
 	return &info, nil
 }