plan, executor: clean code (pingcap#2520)

executor/builder.go

@@ -57,8 +57,6 @@ func (b *executorBuilder) build(p plan.Plan) Executor {
 		return b.buildDeallocate(v)
 	case *plan.Delete:
 		return b.buildDelete(v)
-	case *plan.Distinct:
-		return b.buildDistinct(v)
 	case *plan.Execute:
 		return b.buildExecute(v)
 	case *plan.Explain:
@@ -192,10 +190,6 @@ func (b *executorBuilder) buildLimit(v *plan.Limit) Executor {
 	return e
 }
 
-func (b *executorBuilder) buildDistinct(v *plan.Distinct) Executor {
-	return &DistinctExec{Src: b.build(v.GetChildByIndex(0)), schema: v.GetSchema()}
-}
-
 func (b *executorBuilder) buildPrepare(v *plan.Prepare) Executor {
 	return &PrepareExec{
 		Ctx:     b.ctx,

executor/executor.go

@@ -32,14 +32,12 @@ import (
 	"github.com/pingcap/tidb/table"
 	"github.com/pingcap/tidb/tablecodec"
 	"github.com/pingcap/tidb/terror"
-	"github.com/pingcap/tidb/util/distinct"
 	"github.com/pingcap/tidb/util/types"
 )
 
 var (
 	_ Executor = &ApplyExec{}
 	_ Executor = &CheckTableExec{}
-	_ Executor = &DistinctExec{}
 	_ Executor = &DummyScanExec{}
 	_ Executor = &ExistsExec{}
 	_ Executor = &HashAggExec{}
@@ -309,50 +307,6 @@ type orderByRow struct {
 	row *Row
 }
 
-// DistinctExec represents Distinct executor.
-// It ignores duplicate rows from source Executor by using a *distinct.Checker which maintains
-// a map to check duplication.
-// Because every distinct row will be added to the map, the memory usage might be very high.
-type DistinctExec struct {
-	Src     Executor
-	checker *distinct.Checker
-	schema  expression.Schema
-}
-
-// Schema implements the Executor Schema interface.
-func (e *DistinctExec) Schema() expression.Schema {
-	return e.schema
-}
-
-// Next implements the Executor Next interface.
-func (e *DistinctExec) Next() (*Row, error) {
-	if e.checker == nil {
-		e.checker = distinct.CreateDistinctChecker()
-	}
-	for {
-		row, err := e.Src.Next()
-		if err != nil {
-			return nil, errors.Trace(err)
-		}
-		if row == nil {
-			return nil, nil
-		}
-		ok, err := e.checker.Check(types.DatumsToInterfaces(row.Data))
-		if err != nil {
-			return nil, errors.Trace(err)
-		}
-		if !ok {
-			continue
-		}
-		return row, nil
-	}
-}
-
-// Close implements the Executor Close interface.
-func (e *DistinctExec) Close() error {
-	return e.Src.Close()
-}
-
 // ReverseExec produces reverse ordered result, it is used to wrap executors that do not support reverse scan.
 type ReverseExec struct {
 	Src    Executor

plan/match_property.go

@@ -287,11 +287,6 @@ func (p *Limit) matchProperty(_ *requiredProperty, _ ...*physicalPlanInfo) *phys
 	panic("You can't call this function!")
 }
 
-// matchProperty implements PhysicalPlan matchProperty interface.
-func (p *Distinct) matchProperty(_ *requiredProperty, _ ...*physicalPlanInfo) *physicalPlanInfo {
-	panic("You can't call this function!")
-}
-
 // matchProperty implements PhysicalPlan matchProperty interface.
 func (p *TableDual) matchProperty(_ *requiredProperty, _ ...*physicalPlanInfo) *physicalPlanInfo {
 	panic("You can't call this function!")

plan/physical_plan_builder.go

@@ -1028,29 +1028,6 @@ func (p *Apply) convert2PhysicalPlan(prop *requiredProperty) (*physicalPlanInfo,
 	return info, nil
 }
 
-// convert2PhysicalPlan implements the LogicalPlan convert2PhysicalPlan interface.
-// TODO: support streaming distinct.
-func (p *Distinct) convert2PhysicalPlan(prop *requiredProperty) (*physicalPlanInfo, error) {
-	info, err := p.getPlanInfo(prop)
-	if err != nil {
-		return nil, errors.Trace(err)
-	}
-	if info != nil {
-		return info, nil
-	}
-	child := p.GetChildByIndex(0).(LogicalPlan)
-	limit := prop.limit
-	info, err = child.convert2PhysicalPlan(removeLimit(prop))
-	if err != nil {
-		return nil, errors.Trace(err)
-	}
-	info = addPlanToResponse(p, info)
-	info.count = uint64(float64(info.count) * distinctFactor)
-	info = enforceProperty(limitProperty(limit), info)
-	p.storePlanInfo(prop, info)
-	return info, nil
-}
-
 // physicalInitialize will set value of some attributes after convert2PhysicalPlan process.
 // Currently, only attribute "correlated" is considered.
 func physicalInitialize(p PhysicalPlan) {

plan/physical_plans.go

@@ -666,12 +666,6 @@ func (p *PhysicalHashJoin) SetCorrelated() {
 	}
 }
 
-// Copy implements the PhysicalPlan Copy interface.
-func (p *Distinct) Copy() PhysicalPlan {
-	np := *p
-	return &np
-}
-
 // Copy implements the PhysicalPlan Copy interface.
 func (p *Selection) Copy() PhysicalPlan {
 	np := *p

plan/plans.go

@@ -114,11 +114,6 @@ type Limit struct {
 	Count  uint64
 }
 
-// Distinct represents Distinct plan.
-type Distinct struct {
-	baseLogicalPlan
-}
-
 // Prepare represents prepare plan.
 type Prepare struct {
 	basePlan

plan/stringer.go

@@ -138,8 +138,6 @@ func toString(in Plan, strs []string, idxs []int) ([]string, []int) {
 			}
 		}
 		str += ")"
-	case *Distinct:
-		str = "Distinct"
 	case *Trim:
 		str = "Trim"
 	case *Cache: