planner: move invalidTask to task base pkg. (#53267)

ref #51664, ref #52714

pkg/planner/core/base/task_base.go

@@ -32,3 +32,6 @@ type Task interface {
 	// MemoryUsage returns the memory usage of current task.
 	MemoryUsage() int64
 }
+
+// InvalidTask is just a common invalid singleton instance initialized by core's empty RootTask.
+var InvalidTask Task

pkg/planner/core/core_init.go

@@ -17,6 +17,7 @@ package core
 import (
 	"github.com/pingcap/tidb/pkg/expression"
 	"github.com/pingcap/tidb/pkg/planner/cardinality"
+	"github.com/pingcap/tidb/pkg/planner/core/base"
 	plannerutil "github.com/pingcap/tidb/pkg/planner/util"
 	"github.com/pingcap/tidb/pkg/planner/util/utilfuncp"
 	"github.com/pingcap/tidb/pkg/statistics"
@@ -38,6 +39,7 @@ func init() {
 	statistics.PrepareCols4MVIndex = PrepareIdxColsAndUnwrapArrayType
 
 	// For basic optimizer init.
+	base.InvalidTask = &RootTask{} // invalid if p is nil
 	expression.EvalSimpleAst = evalAstExpr
 	expression.BuildSimpleExpr = buildSimpleExpr
 	expression.DecodeKeyFromString = decodeKeyFromString

pkg/planner/core/plan.go

@@ -48,11 +48,11 @@ func enforceProperty(p *property.PhysicalProperty, tsk base.Task, ctx base.PlanC
 	if p.TaskTp == property.MppTaskType {
 		mpp, ok := tsk.(*MppTask)
 		if !ok || mpp.Invalid() {
-			return invalidTask
+			return base.InvalidTask
 		}
 		if !p.IsSortItemAllForPartition() {
 			ctx.GetSessionVars().RaiseWarningWhenMPPEnforced("MPP mode may be blocked because operator `Sort` is not supported now.")
-			return invalidTask
+			return base.InvalidTask
 		}
 		tsk = mpp.enforceExchanger(p)
 	}

pkg/planner/core/task.go

@@ -387,12 +387,12 @@ func (p *PhysicalHashJoin) attach2TaskForMpp(tasks ...base.Task) base.Task {
 	lTask, lok := tasks[0].(*MppTask)
 	rTask, rok := tasks[1].(*MppTask)
 	if !lok || !rok {
-		return invalidTask
+		return base.InvalidTask
 	}
 	if p.mppShuffleJoin {
 		// protection check is case of some bugs
 		if len(lTask.hashCols) != len(rTask.hashCols) || len(lTask.hashCols) == 0 {
-			return invalidTask
+			return base.InvalidTask
 		}
 		lTask, rTask = p.convertPartitionKeysIfNeed(lTask, rTask)
 	}
@@ -1017,7 +1017,7 @@ func (p *PhysicalExpand) Attach2Task(tasks ...base.Task) base.Task {
 		mpp.p = p
 		return mpp
 	}
-	return invalidTask
+	return base.InvalidTask
 }
 
 // Attach2Task implements PhysicalPlan interface.
@@ -1052,11 +1052,11 @@ func (p *PhysicalUnionAll) attach2MppTasks(tasks ...base.Task) base.Task {
 		} else if root, ok := tk.(*RootTask); ok && root.IsEmpty() {
 			continue
 		} else {
-			return invalidTask
+			return base.InvalidTask
 		}
 	}
 	if len(childPlans) == 0 {
-		return invalidTask
+		return base.InvalidTask
 	}
 	p.SetChildren(childPlans...)
 	return t
@@ -1069,8 +1069,8 @@ func (p *PhysicalUnionAll) Attach2Task(tasks ...base.Task) base.Task {
 			if p.TP() == plancodec.TypePartitionUnion {
 				// In attach2MppTasks(), will attach PhysicalUnion to mppTask directly.
 				// But PartitionUnion cannot pushdown to tiflash, so here disable PartitionUnion pushdown to tiflash explicitly.
-				// For now, return invalidTask immediately, we can refine this by letting childTask of PartitionUnion convert to rootTask.
-				return invalidTask
+				// For now, return base.InvalidTask immediately, we can refine this by letting childTask of PartitionUnion convert to rootTask.
+				return base.InvalidTask
 			}
 			return p.attach2MppTasks(tasks...)
 		}
@@ -1758,7 +1758,7 @@ func (p *PhysicalStreamAgg) Attach2Task(tasks ...base.Task) base.Task {
 			storeType := cop.getStoreType()
 			// TiFlash doesn't support Stream Aggregation
 			if storeType == kv.TiFlash && len(p.GroupByItems) > 0 {
-				return invalidTask
+				return base.InvalidTask
 			}
 			partialAgg, finalAgg := p.newPartialAggregate(storeType, false)
 			if partialAgg != nil {
@@ -2122,7 +2122,7 @@ func (p *PhysicalHashAgg) attach2TaskForMpp(tasks ...base.Task) base.Task {
 	t := tasks[0].Copy()
 	mpp, ok := t.(*MppTask)
 	if !ok {
-		return invalidTask
+		return base.InvalidTask
 	}
 	switch p.MppRunMode {
 	case Mpp1Phase:
@@ -2139,7 +2139,7 @@ func (p *PhysicalHashAgg) attach2TaskForMpp(tasks ...base.Task) base.Task {
 		proj := p.convertAvgForMPP()
 		partialAgg, finalAgg := p.newPartialAggregate(kv.TiFlash, true)
 		if partialAgg == nil {
-			return invalidTask
+			return base.InvalidTask
 		}
 		attachPlan2Task(partialAgg, mpp)
 		partitionCols := p.MppPartitionCols
@@ -2149,7 +2149,7 @@ func (p *PhysicalHashAgg) attach2TaskForMpp(tasks ...base.Task) base.Task {
 			for _, expr := range items {
 				col, ok := expr.(*expression.Column)
 				if !ok {
-					return invalidTask
+					return base.InvalidTask
 				}
 				partitionCols = append(partitionCols, &property.MPPPartitionColumn{
 					Col:       col,
@@ -2188,12 +2188,12 @@ func (p *PhysicalHashAgg) attach2TaskForMpp(tasks ...base.Task) base.Task {
 		proj := p.convertAvgForMPP()
 		partialAgg, finalAgg := p.newPartialAggregate(kv.TiFlash, true)
 		if finalAgg == nil {
-			return invalidTask
+			return base.InvalidTask
 		}
 
 		final, middle, partial, proj4Partial, err := p.adjust3StagePhaseAgg(partialAgg, finalAgg, canUse3StageAgg, groupingSets, mpp)
 		if err != nil {
-			return invalidTask
+			return base.InvalidTask
 		}
 
 		// partial agg proj would be null if one scalar agg cannot run in two-phase mode
@@ -2241,7 +2241,7 @@ func (p *PhysicalHashAgg) attach2TaskForMpp(tasks ...base.Task) base.Task {
 		attachPlan2Task(proj, newMpp)
 		return newMpp
 	default:
-		return invalidTask
+		return base.InvalidTask
 	}
 }
 

pkg/planner/core/task_base.go

@@ -201,7 +201,7 @@ func (t *MppTask) ConvertToRootTaskImpl(ctx base.PlanContext) *RootTask {
 			// It's only for TableScan. This is ensured by converting mppTask to rootTask just after TableScan is built,
 			// so no other operators are added into this mppTask.
 			logutil.BgLogger().Error("expect Selection or TableScan for mppTask.p", zap.String("mppTask.p", t.p.TP()))
-			return invalidTask
+			return base.InvalidTask.(*RootTask)
 		}
 		selectivity, _, err := cardinality.Selectivity(ctx, t.tblColHists, t.rootTaskConds, nil)
 		if err != nil {

pkg/planner/util/utilfuncp/func_pointer_misc.go

@@ -48,6 +48,6 @@ var GetTaskPlanCost func(t base.Task, pop *optimizetrace.PhysicalOptimizeOp) (fl
 
 // AddSelection will add a selection if necessary.
 // This function is util function pointer that initialized by core functionality.
-// todo: (3) arenatlx, remove this func pointer when inside referred LogicalSelection is moved out of core.
+// todo: (4) arenatlx, remove this func pointer when inside referred LogicalSelection is moved out of core.
 var AddSelection func(p base.LogicalPlan, child base.LogicalPlan, conditions []expression.Expression,
 	chIdx int, opt *optimizetrace.LogicalOptimizeOp)