Count how many shards were hit by routes when using vexplain

go/vt/vtgate/engine/fake_vcursor_test.go

@@ -132,7 +132,7 @@ func (t *noopVCursor) UnresolvedTransactions(ctx context.Context, keyspace strin
 	panic("implement me")
 }
 
-func (t *noopVCursor) StartPrimitiveTrace() func() map[Primitive]RowsReceived {
+func (t *noopVCursor) StartPrimitiveTrace() func() Stats {
 	panic("implement me")
 }
 

go/vt/vtgate/engine/plan_description.go

@@ -48,7 +48,8 @@ type PrimitiveDescription struct {
 	InputName string
 	Inputs    []PrimitiveDescription
 
-	Stats RowsReceived
+	RowsReceived  RowsReceived
+	ShardsQueried *ShardsQueried
 }
 
 // MarshalJSON serializes the PlanDescription into a JSON representation.
@@ -92,15 +93,20 @@ func (pd PrimitiveDescription) MarshalJSON() ([]byte, error) {
 			return nil, err
 		}
 	}
-	if len(pd.Stats) > 0 {
-		if err := marshalAdd(prepend, buf, "NoOfCalls", len(pd.Stats)); err != nil {
+	if len(pd.RowsReceived) > 0 {
+		if err := marshalAdd(prepend, buf, "NoOfCalls", len(pd.RowsReceived)); err != nil {
 			return nil, err
 		}
 
-		if err := marshalAdd(prepend, buf, "AvgNumberOfRows", average(pd.Stats)); err != nil {
+		if err := marshalAdd(prepend, buf, "AvgNumberOfRows", average(pd.RowsReceived)); err != nil {
 			return nil, err
 		}
-		if err := marshalAdd(prepend, buf, "MedianNumberOfRows", median(pd.Stats)); err != nil {
+		if err := marshalAdd(prepend, buf, "MedianNumberOfRows", median(pd.RowsReceived)); err != nil {
+			return nil, err
+		}
+	}
+	if pd.ShardsQueried != nil {
+		if err := marshalAdd(prepend, buf, "ShardsQueried", pd.ShardsQueried); err != nil {
 			return nil, err
 		}
 	}
@@ -219,10 +225,16 @@ func marshalAdd(prepend string, buf *bytes.Buffer, name string, obj any) error {
 
 // PrimitiveToPlanDescription transforms a primitive tree into a corresponding PlanDescription tree
 // If stats is not nil, it will be used to populate the stats field of the PlanDescription
-func PrimitiveToPlanDescription(in Primitive, stats map[Primitive]RowsReceived) PrimitiveDescription {
+func PrimitiveToPlanDescription(in Primitive, stats *Stats) PrimitiveDescription {
 	this := in.description()
 	if stats != nil {
-		this.Stats = stats[in]
+		this.RowsReceived = stats.InterOpStats[in]
+
+		// Only applies to Route primitive
+		v, ok := stats.ShardsStats[in]
+		if ok {
+			this.ShardsQueried = &v
+		}
 	}
 
 	inputs, infos := in.Inputs()

go/vt/vtgate/engine/primitive.go

@@ -143,7 +143,7 @@ type (
 
 		// StartPrimitiveTrace starts a trace for the given primitive,
 		// and returns a function to get the trace logs after the primitive execution.
-		StartPrimitiveTrace() func() map[Primitive]RowsReceived
+		StartPrimitiveTrace() func() Stats
 	}
 
 	// SessionActions gives primitives ability to interact with the session state

go/vt/vtgate/engine/vexplain.go

@@ -44,7 +44,13 @@ type (
 		Type  sqlparser.VExplainType
 	}
 
-	RowsReceived []int
+	ShardsQueried int
+	RowsReceived  []int
+
+	Stats struct {
+		InterOpStats map[Primitive]RowsReceived
+		ShardsStats  map[Primitive]ShardsQueried
+	}
 )
 
 var _ Primitive = (*VExplain)(nil)
@@ -111,7 +117,7 @@ func (v *VExplain) NeedsTransaction() bool {
 
 // TryExecute implements the Primitive interface
 func (v *VExplain) TryExecute(ctx context.Context, vcursor VCursor, bindVars map[string]*querypb.BindVariable, wantfields bool) (*sqltypes.Result, error) {
-	var stats func() map[Primitive]RowsReceived
+	var stats func() Stats
 	if v.Type == sqlparser.TraceVExplainType {
 		stats = vcursor.StartPrimitiveTrace()
 	} else {
@@ -130,7 +136,7 @@ func noOpCallback(*sqltypes.Result) error {
 
 // TryStreamExecute implements the Primitive interface
 func (v *VExplain) TryStreamExecute(ctx context.Context, vcursor VCursor, bindVars map[string]*querypb.BindVariable, wantfields bool, callback func(*sqltypes.Result) error) error {
-	var stats func() map[Primitive]RowsReceived
+	var stats func() Stats
 	if v.Type == sqlparser.TraceVExplainType {
 		stats = vcursor.StartPrimitiveTrace()
 	} else {
@@ -148,7 +154,7 @@ func (v *VExplain) TryStreamExecute(ctx context.Context, vcursor VCursor, bindVa
 	return callback(result)
 }
 
-func (v *VExplain) convertToResult(ctx context.Context, vcursor VCursor, stats func() map[Primitive]RowsReceived) (*sqltypes.Result, error) {
+func (v *VExplain) convertToResult(ctx context.Context, vcursor VCursor, stats func() Stats) (*sqltypes.Result, error) {
 	switch v.Type {
 	case sqlparser.QueriesVExplainType:
 		result := convertToVExplainQueriesResult(vcursor.Session().GetVExplainLogs())
@@ -163,8 +169,9 @@ func (v *VExplain) convertToResult(ctx context.Context, vcursor VCursor, stats f
 	}
 }
 
-func (v *VExplain) getExplainTraceOutput(getOpStats func() map[Primitive]RowsReceived) (*sqltypes.Result, error) {
-	description := PrimitiveToPlanDescription(v.Input, getOpStats())
+func (v *VExplain) getExplainTraceOutput(getOpStats func() Stats) (*sqltypes.Result, error) {
+	stats := getOpStats()
+	description := PrimitiveToPlanDescription(v.Input, &stats)
 
 	output, err := json.MarshalIndent(description, "", "\t")
 	if err != nil {

go/vt/vtgate/executor_vexplain_test.go

@@ -94,9 +94,10 @@ func TestSimpleVexplainTrace(t *testing.T) {
 				"Name": "TestExecutor",
 				"Sharded": true
 			},
-			"NoOfCalls": 2,
+			"NoOfCalls": 1,
 			"AvgNumberOfRows": 16,
 			"MedianNumberOfRows": 16,
+			"ShardsQueried": 8,
 			"FieldQuery": "select count(*), col2, weight_string(col2) from music where 1 != 1 group by col2, weight_string(col2)",
 			"OrderBy": "(1|2) ASC",
 			"Query": "select count(*), col2, weight_string(col2) from music group by col2, weight_string(col2) order by col2 asc",

go/vt/vtgate/vcursor_impl.go

@@ -135,7 +135,8 @@ type (
 
 		// this is a map of the number of rows that every primitive has returned
 		// if this field is nil, it means that we are not logging operator traffic
-		primitiveStats map[engine.Primitive]engine.RowsReceived
+		interOpStats map[engine.Primitive]engine.RowsReceived
+		shardsStats  map[engine.Primitive]engine.ShardsQueried
 	}
 )
 
@@ -285,10 +286,14 @@ func (vc *vcursorImpl) UnresolvedTransactions(ctx context.Context, keyspace stri
 	return vc.executor.UnresolvedTransactions(ctx, targets)
 }
 
-func (vc *vcursorImpl) StartPrimitiveTrace() func() map[engine.Primitive]engine.RowsReceived {
-	vc.primitiveStats = make(map[engine.Primitive]engine.RowsReceived)
-	return func() map[engine.Primitive]engine.RowsReceived {
-		return vc.primitiveStats
+func (vc *vcursorImpl) StartPrimitiveTrace() func() engine.Stats {
+	vc.interOpStats = make(map[engine.Primitive]engine.RowsReceived)
+	vc.shardsStats = make(map[engine.Primitive]engine.ShardsQueried)
+	return func() engine.Stats {
+		return engine.Stats{
+			InterOpStats: vc.interOpStats,
+			ShardsStats:  vc.shardsStats,
+		}
 	}
 }
 
@@ -532,14 +537,20 @@ func (vc *vcursorImpl) ExecutePrimitive(ctx context.Context, primitive engine.Pr
 }
 
 func (vc *vcursorImpl) logOpTraffic(primitive engine.Primitive, res *sqltypes.Result) {
-	if vc.primitiveStats != nil {
-		rows := vc.primitiveStats[primitive]
+	if vc.interOpStats != nil {
+		rows := vc.interOpStats[primitive]
 		if res == nil {
 			rows = append(rows, 0)
 		} else {
 			rows = append(rows, len(res.Rows))
 		}
-		vc.primitiveStats[primitive] = rows
+		vc.interOpStats[primitive] = rows
+	}
+}
+
+func (vc *vcursorImpl) logShardsQueried(primitive engine.Primitive, shardsNb int) {
+	if vc.shardsStats != nil {
+		vc.shardsStats[primitive] += engine.ShardsQueried(shardsNb)
 	}
 }
 
@@ -558,7 +569,7 @@ func (vc *vcursorImpl) ExecutePrimitiveStandalone(ctx context.Context, primitive
 }
 
 func (vc *vcursorImpl) wrapCallback(callback func(*sqltypes.Result) error, primitive engine.Primitive) func(*sqltypes.Result) error {
-	if vc.primitiveStats == nil {
+	if vc.interOpStats == nil {
 		return callback
 	}
 
@@ -650,7 +661,7 @@ func (vc *vcursorImpl) ExecuteMultiShard(ctx context.Context, primitive engine.P
 
 	qr, errs := vc.executor.ExecuteMultiShard(ctx, primitive, rss, commentedShardQueries(queries, vc.marginComments), vc.safeSession, canAutocommit, vc.ignoreMaxMemoryRows, vc.resultsObserver)
 	vc.setRollbackOnPartialExecIfRequired(len(errs) != len(rss), rollbackOnError)
-	vc.logOpTraffic(primitive, qr)
+	vc.logShardsQueried(primitive, len(rss))
 	return qr, errs
 }
 
@@ -689,7 +700,7 @@ func (vc *vcursorImpl) ExecuteStandalone(ctx context.Context, primitive engine.P
 	// The autocommit flag is always set to false because we currently don't
 	// execute DMLs through ExecuteStandalone.
 	qr, errs := vc.executor.ExecuteMultiShard(ctx, primitive, rss, bqs, NewAutocommitSession(vc.safeSession.Session), false /* autocommit */, vc.ignoreMaxMemoryRows, vc.resultsObserver)
-	vc.logOpTraffic(primitive, qr)
+	vc.logShardsQueried(primitive, len(rss))
 	return qr, vterrors.Aggregate(errs)
 }