*: address comments

executor/executor.go

@@ -91,7 +91,7 @@ type Executor interface {
 type ShowDDL struct {
 	fields []*ast.ResultField
 	ctx    context.Context
-	cnt    int
+	done   bool
 }
 
 // Fields implements Executor Fields interface.
@@ -101,7 +101,7 @@ func (e *ShowDDL) Fields() []*ast.ResultField {
 
 // Next implements Execution Next interface.
 func (e *ShowDDL) Next() (*Row, error) {
-	if e.cnt != 0 {
+	if e.done {
 		return nil, nil
 	}
 
@@ -115,23 +115,23 @@ func (e *ShowDDL) Next() (*Row, error) {
 		return nil, errors.Trace(err)
 	}
 
-	records := []interface{}{
+	rowData := []interface{}{
 		info.SchemaVer,
 		nil,
 		nil,
 	}
 	if info.Owner != nil {
-		records[1] = info.Owner.String()
+		rowData[1] = info.Owner.String()
 	}
 	if info.Job != nil {
-		records[2] = info.Job.String()
+		rowData[2] = info.Job.String()
 	}
 	row := &Row{}
-	row.Data = append(row.Data, records...)
+	row.Data = rowData
 	for i, f := range e.fields {
-		f.Expr.SetValue(records[i])
+		f.Expr.SetValue(rowData[i])
 	}
-	e.cnt++
+	e.done = true
 
 	return row, nil
 }
@@ -145,6 +145,7 @@ func (e *ShowDDL) Close() error {
 type CheckTable struct {
 	tables []*ast.TableName
 	ctx    context.Context
+	done   bool
 }
 
 // Fields implements Executor Fields interface.
@@ -154,6 +155,10 @@ func (e *CheckTable) Fields() []*ast.ResultField {
 
 // Next implements Execution Next interface.
 func (e *CheckTable) Next() (*Row, error) {
+	if e.done {
+		return nil, nil
+	}
+
 	dbName := model.NewCIStr(db.GetCurrentSchema(e.ctx))
 	is := sessionctx.GetDomain(e.ctx).InfoSchema()
 	txn, err := e.ctx.GetTxn(false)
@@ -173,6 +178,7 @@ func (e *CheckTable) Next() (*Row, error) {
 			}
 		}
 	}
+	e.done = true
 
 	return nil, nil
 }

executor/executor_test.go

@@ -53,6 +53,7 @@ func (s *testSuite) TestAdmin(c *C) {
 	c.Assert(err, IsNil)
 	row, err := r.Next()
 	c.Assert(err, IsNil)
+	c.Logf("row:%v\n", row)
 	c.Assert(row, NotNil)
 
 	r, err = tk.Exec("admin check table admin_test")

optimizer/plan/alternatives.go

@@ -23,16 +23,14 @@ func Alternatives(p Plan) ([]Plan, error) {
 	case nil:
 	case *TableScan:
 		plans = tableScanAlternatives(x)
-	case *ShowDDL:
-		plans = showDDLAlternatives(x)
-	case *CheckTable:
-		plans = checkTableAlternatives(x)
 	case WithSrcPlan:
 		var err error
 		plans, err = planWithSrcAlternatives(x)
 		if err != nil {
 			return nil, errors.Trace(err)
 		}
+	case *ShowDDL:
+	case *CheckTable:
 	case *Prepare:
 	case *Execute:
 	case *Deallocate:
@@ -67,17 +65,6 @@ func tableScanAlternatives(p *TableScan) []Plan {
 	return alts
 }
 
-func showDDLAlternatives(p *ShowDDL) []Plan {
-	sp := &ShowDDL{}
-	sp.SetFields(p.fields)
-
-	return []Plan{sp}
-}
-
-func checkTableAlternatives(p *CheckTable) []Plan {
-	return []Plan{&CheckTable{}}
-}
-
 // planWithSrcAlternatives shallow copies the WithSrcPlan,
 // and set its src to src alternatives.
 func planWithSrcAlternatives(p WithSrcPlan) ([]Plan, error) {

optimizer/plan/planbuilder.go

@@ -34,9 +34,6 @@ const (
 	CodeUnsupportedType = iota + 1
 )
 
-// Table Name.
-const tableShowDDL = "SHOW_DDL"
-
 // BuildPlan builds a plan from a node.
 // returns ErrUnsupportedType if ast.Node type is not supported yet.
 func BuildPlan(node ast.Node) (Plan, error) {
@@ -216,11 +213,7 @@ func (b *planBuilder) buildPrepare(x *ast.PrepareStmt) Plan {
 
 func (b *planBuilder) buildAdmin(adm *ast.AdminStmt) Plan {
 	if adm.Tp == ast.AdminCheckTable {
-		if adm.Tables != nil {
-			return &CheckTable{Tables: adm.Tables}
-		}
-
-		return nil
+		return &CheckTable{Tables: adm.Tables}
 	}
 
 	if adm.Tp == ast.AdminShowDDL {
@@ -230,15 +223,16 @@ func (b *planBuilder) buildAdmin(adm *ast.AdminStmt) Plan {
 		return p
 	}
 
+	b.err = ErrUnsupportedType.Gen("Unsupported type %T", adm)
+
 	return nil
 }
 
 func buildShowDDLFields() []*ast.ResultField {
-	tbName := tableShowDDL
 	rfs := make([]*ast.ResultField, 0, 3)
-	rfs = append(rfs, buildResultField(tbName, "SCHEMA_VER", mysql.TypeLonglong, 4))
-	rfs = append(rfs, buildResultField(tbName, "OWNER", mysql.TypeVarchar, 64))
-	rfs = append(rfs, buildResultField(tbName, "Job", mysql.TypeVarchar, 128))
+	rfs = append(rfs, buildResultField("", "SCHEMA_VER", mysql.TypeLonglong, 4))
+	rfs = append(rfs, buildResultField("", "OWNER", mysql.TypeVarchar, 64))
+	rfs = append(rfs, buildResultField("", "Job", mysql.TypeVarchar, 128))
 
 	return rfs
 }