don't DoOptimze when build show

executor/builder.go

@@ -1183,11 +1183,16 @@ func (b *executorBuilder) buildTableDual(v *plannercore.PhysicalTableDual) Execu
 		return nil
 	}
 	base := newBaseExecutor(b.ctx, v.Schema(), v.ExplainID())
-	base.initCap = v.RowCount
 	e := &TableDualExec{
 		baseExecutor: base,
 		numDualRows:  v.RowCount,
 	}
+	if v.SourcePlan != nil {
+		sourceExec := b.build(v.SourcePlan)
+		e.sourceExec = sourceExec
+	} else {
+		base.initCap = v.RowCount
+	}
 	return e
 }
 

executor/executor.go

@@ -953,6 +953,9 @@ type TableDualExec struct {
 	// numDualRows can only be 0 or 1.
 	numDualRows int
 	numReturned int
+
+	// Temp solution to make the logic of processing show statement more reasonable.
+	sourceExec Executor
 }
 
 // Open implements the Executor Open interface.
@@ -963,6 +966,9 @@ func (e *TableDualExec) Open(ctx context.Context) error {
 
 // Next implements the Executor Next interface.
 func (e *TableDualExec) Next(ctx context.Context, req *chunk.Chunk) error {
+	if e.sourceExec != nil {
+		return e.sourceExec.Next(ctx, req)
+	}
 	req.Reset()
 	if e.numReturned >= e.numDualRows {
 		return nil

planner/core/common_plans.go

@@ -368,6 +368,7 @@ type Deallocate struct {
 }
 
 // Show represents a show plan.
+// TODO: make as a logical data source or table dual.
 type Show struct {
 	physicalSchemaProducer
 

planner/core/find_best_task.go

@@ -68,8 +68,8 @@ func (p *LogicalTableDual) findBestTask(prop *property.PhysicalProperty) (task,
 		return invalidTask, nil
 	}
 	dual := PhysicalTableDual{
-		RowCount:    p.RowCount,
-		placeHolder: p.placeHolder,
+		RowCount:   p.RowCount,
+		SourcePlan: p.sourcePlan,
 	}.Init(p.ctx, p.stats)
 	dual.SetSchema(p.schema)
 	return &rootTask{p: dual}, nil

planner/core/logical_plans.go

@@ -313,10 +313,8 @@ type LogicalTableDual struct {
 	logicalSchemaProducer
 
 	RowCount int
-	// placeHolder indicates if this dual plan is a place holder in query optimization
-	// for data sources like `Show`, if true, the dual plan would be substituted by
-	// `Show` in the final plan.
-	placeHolder bool
+
+	sourcePlan Plan
 }
 
 // LogicalUnionScan is only used in non read-only txn.

planner/core/physical_plans.go

@@ -410,10 +410,8 @@ type PhysicalTableDual struct {
 	physicalSchemaProducer
 
 	RowCount int
-	// placeHolder indicates if this dual plan is a place holder in query optimization
-	// for data sources like `Show`, if true, the dual plan would be substituted by
-	// `Show` in the final plan.
-	placeHolder bool
+
+	SourcePlan Plan
 
 	// names is used for OutputNames() method. Dual may be inited when building point get plan.
 	// So it needs to hold names for itself.

planner/core/planbuilder.go

@@ -1374,7 +1374,7 @@ func (b *PlanBuilder) buildShow(ctx context.Context, show *ast.ShowStmt) (Plan,
 	for _, col := range p.schema.Columns {
 		col.UniqueID = b.ctx.GetSessionVars().AllocPlanColumnID()
 	}
-	mockTablePlan := LogicalTableDual{placeHolder: true}.Init(b.ctx)
+	mockTablePlan := LogicalTableDual{sourcePlan: p}.Init(b.ctx)
 	mockTablePlan.SetSchema(p.schema)
 	var err error
 	var np LogicalPlan
@@ -1406,26 +1406,11 @@ func (b *PlanBuilder) buildShow(ctx context.Context, show *ast.ShowStmt) (Plan,
 		}
 		proj.SetSchema(schema)
 		proj.SetChildren(np)
-		physical, err := DoOptimize(ctx, b.optFlag|flagEliminateProjection, proj)
-		if err != nil {
-			return nil, err
-		}
-		return substitutePlaceHolderDual(physical, p), nil
+		return proj, nil
 	}
 	return p, nil
 }
 
-func substitutePlaceHolderDual(src PhysicalPlan, dst PhysicalPlan) PhysicalPlan {
-	if dual, ok := src.(*PhysicalTableDual); ok && dual.placeHolder {
-		return dst
-	}
-	for i, child := range src.Children() {
-		newChild := substitutePlaceHolderDual(child, dst)
-		src.SetChild(i, newChild)
-	}
-	return src
-}
-
 func (b *PlanBuilder) buildSimple(node ast.StmtNode) (Plan, error) {
 	p := &Simple{Statement: node}