plan: make plan reusable after close

plan/plan.go

@@ -47,6 +47,7 @@ type Plan interface {
 	Next(ctx context.Context) (row *Row, err error)
 
 	// Close closes the underlying iterator of the plan.
+	// If you call Next after Close, it will start iteration from beginning.
 	Close() error
 }
 

plan/plans/distinct.go

@@ -147,6 +147,8 @@ func (r *DistinctDefaultPlan) fetchAll(ctx context.Context) error {
 
 // Close implements plan.Plan Close interface.
 func (r *DistinctDefaultPlan) Close() error {
+	r.rows = nil
+	r.cursor = 0
 	return r.Src.Close()
 }
 

plan/plans/explain.go

@@ -92,6 +92,8 @@ func (r *ExplainDefaultPlan) Next(ctx context.Context) (row *plan.Row, err error
 
 // Close implements plan.Plan Close interface.
 func (r *ExplainDefaultPlan) Close() error {
+	r.lines = nil
+	r.cursor = 0
 	return nil
 }
 

plan/plans/fields.go

@@ -167,6 +167,7 @@ func (s *SelectEmptyFieldListPlan) Next(ctx context.Context) (row *plan.Row, err
 
 // Close implements plan.Plan Close interface.
 func (s *SelectEmptyFieldListPlan) Close() error {
+	s.done = false
 	return nil
 }
 

plan/plans/fields_test.go

@@ -76,10 +76,10 @@ func (s *testFieldsSuit) TestDefaultFieldsPlan(c *C) {
 			},
 		},
 	}
-
+	tblPlan.Close()
 	rset.Plan = &plans.SelectFieldsDefaultPlan{
 		SelectList: sl2,
-		Src:        tblPlan.reset(),
+		Src:        tblPlan,
 	}
 
 	rset.Do(func(data []interface{}) (bool, error) {
@@ -99,9 +99,10 @@ func (s *testFieldsSuit) TestDefaultFieldsPlan(c *C) {
 			},
 		},
 	}
+	tblPlan.Close()
 	rset.Plan = &plans.SelectFieldsDefaultPlan{
 		SelectList: sl3,
-		Src:        tblPlan.reset(),
+		Src:        tblPlan,
 	}
 	err := rset.Do(func(data []interface{}) (bool, error) {
 		return true, nil

plan/plans/final.go

@@ -107,6 +107,7 @@ func (r *SelectFinalPlan) Next(ctx context.Context) (row *plan.Row, err error) {
 
 // Close implements plan.Plan Close interface.
 func (r *SelectFinalPlan) Close() error {
+	r.infered = false
 	return r.Src.Close()
 }
 

plan/plans/from.go

@@ -124,7 +124,10 @@ func (r *TableNilPlan) Next(ctx context.Context) (row *plan.Row, err error) {
 
 // Close implements plan.Plan Close interface.
 func (r *TableNilPlan) Close() error {
-	r.iter.Close()
+	if r.iter != nil {
+		r.iter.Close()
+	}
+	r.iter = nil
 	return nil
 }
 
@@ -411,7 +414,10 @@ func (r *TableDefaultPlan) Next(ctx context.Context) (row *plan.Row, err error)
 
 // Close implements plan.Plan Close interface.
 func (r *TableDefaultPlan) Close() error {
-	r.iter.Close()
+	if r.iter != nil {
+		r.iter.Close()
+	}
+	r.iter = nil
 	return nil
 }
 

plan/plans/index.go

@@ -427,7 +427,10 @@ func (r *indexPlan) Next(ctx context.Context) (row *plan.Row, err error) {
 func (r *indexPlan) Close() error {
 	if r.iter != nil {
 		r.iter.Close()
+		r.iter = nil
 	}
+	r.cursor = 0
+	r.skipLowCmp = false
 	return nil
 }
 

plan/plans/info.go

@@ -584,6 +584,8 @@ func (isp *InfoSchemaPlan) fetchCharacterSets() {
 
 // Close implements plan.Plan Close interface.
 func (isp *InfoSchemaPlan) Close() error {
+	isp.rows = nil
+	isp.cursor = 0
 	return nil
 }
 

plan/plans/limit.go

@@ -89,6 +89,7 @@ func (r *LimitDefaultPlan) Next(ctx context.Context) (row *plan.Row, err error)
 
 // Close implements plan.Plan Close interface.
 func (r *LimitDefaultPlan) Close() error {
+	r.cursor = 0
 	return r.Src.Close()
 }
 
@@ -147,6 +148,7 @@ func (r *OffsetDefaultPlan) Next(ctx context.Context) (row *plan.Row, err error)
 
 // Close implements plan.Plan Close interface.
 func (r *OffsetDefaultPlan) Close() error {
+	r.cursor = 0
 	return r.Src.Close()
 }
 

plan/plans/limit_test.go

@@ -73,6 +73,7 @@ func (p *testTablePlan) Next(ctx context.Context) (row *plan.Row, err error) {
 }
 
 func (p *testTablePlan) Close() error {
+	p.cursor = 0
 	return nil
 }
 
@@ -80,11 +81,6 @@ func (p *testTablePlan) UseNext() bool {
 	return true
 }
 
-func (p *testTablePlan) reset() *testTablePlan {
-	p.cursor = 0
-	return p
-}
-
 type testLimitSuit struct {
 	data []*testRowData
 	sess tidb.Session

plan/plans/orderby.go

@@ -261,6 +261,8 @@ func (r *OrderByDefaultPlan) fetchAll(ctx context.Context) error {
 
 // Close implements plan.Plan Close interface.
 func (r *OrderByDefaultPlan) Close() error {
+	r.ordTable = nil
+	r.cursor = 0
 	return r.Src.Close()
 }
 

plan/plans/show.go

@@ -369,6 +369,8 @@ func (s *ShowPlan) fetchAll(ctx context.Context) error {
 
 // Close implements plan.Plan Close interface.
 func (s *ShowPlan) Close() error {
+	s.rows = nil
+	s.cursor = 0
 	return nil
 }
 
@@ -376,9 +378,3 @@ func (s *ShowPlan) Close() error {
 func (s *ShowPlan) UseNext() bool {
 	return true
 }
-
-// Reset used for test
-func (s *ShowPlan) Reset() {
-	s.rows = nil
-	s.cursor = 0
-}

plan/plans/show_test.go

@@ -91,7 +91,7 @@ func (p *testShowSuit) TestShowVariables(c *C) {
 	c.Assert(v, Equals, "latin1")
 	// Set session variable to utf8
 	sessionVars.Systems["character_set_results"] = "utf8"
-	pln.Reset()
+	pln.Close()
 	rset.Do(func(data []interface{}) (bool, error) {
 		ret[data[0].(string)] = data[1].(string)
 		return true, nil
@@ -103,7 +103,7 @@ func (p *testShowSuit) TestShowVariables(c *C) {
 	c.Assert(v, Equals, "latin1")
 
 	pln.GlobalScope = false
-	pln.Reset()
+	pln.Close()
 	rset.Do(func(data []interface{}) (bool, error) {
 		ret[data[0].(string)] = data[1].(string)
 		return true, nil