Fix executor scatter stats divide by zero issue

go/vt/vtgate/executor_scatter_stats.go

@@ -48,6 +48,25 @@ type statsResultItem struct {
 	Count                  uint64
 }
 
+func castToFloat64(input interface{}) float64 {
+	switch input.(type) {
+	case int64:
+		return float64(input.(int64))
+	case uint64:
+		return float64(input.(uint64))
+	case time.Duration:
+		return float64(input.(time.Duration))
+	}
+	return 0
+}
+
+func divideOrReturnZero(dividend, divisor interface{}) float64 {
+	if castToFloat64(divisor) == 0 {
+		return 0
+	}
+	return castToFloat64(dividend) / castToFloat64(divisor)
+}
+
 func (e *Executor) gatherScatterStats() (statsResults, error) {
 	scatterExecTime := time.Duration(0)
 	readOnlyTime := time.Duration(0)
@@ -91,11 +110,11 @@ func (e *Executor) gatherScatterStats() (statsResults, error) {
 		route := routes[i]
 		resultItems[i] = &statsResultItem{
 			Query:                  plan.Original,
-			AvgTimePerQuery:        time.Duration(plan.ExecTime.Nanoseconds() / int64(plan.ExecCount)),
-			PercentTimeOfReads:     float64(100 * plan.ExecTime / readOnlyTime),
-			PercentTimeOfScatters:  float64(100 * plan.ExecTime / scatterExecTime),
-			PercentCountOfReads:    float64(100 * plan.ExecCount / readOnlyCount),
-			PercentCountOfScatters: float64(100 * plan.ExecCount / scatterCount),
+			AvgTimePerQuery:        time.Duration(divideOrReturnZero(plan.ExecTime.Nanoseconds(), plan.ExecCount)),
+			PercentTimeOfReads:     100 * divideOrReturnZero(plan.ExecTime, readOnlyTime),
+			PercentTimeOfScatters:  100 * divideOrReturnZero(plan.ExecTime, scatterExecTime),
+			PercentCountOfReads:    100 * divideOrReturnZero(plan.ExecCount, readOnlyCount),
+			PercentCountOfScatters: 100 * divideOrReturnZero(plan.ExecCount, scatterCount),
 			From:                   route.Keyspace.Name + "." + route.TableName,
 			Count:                  plan.ExecCount,
 		}

go/vt/vtgate/executor_scatter_stats_test.go

@@ -19,6 +19,9 @@ package vtgate
 import (
 	"context"
 	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
 
 	"net/http/httptest"
 
@@ -76,3 +79,37 @@ func TestScatterStatsHttpWriting(t *testing.T) {
 	require.Contains(t, recorder.Body.String(), query4)
 	require.NoError(t, err)
 }
+
+func TestDivideOrReturnZero(t *testing.T) {
+	// Expected types
+	timeDurationZero := time.Duration(0)
+	unitZero := uint64(0)
+	intZero := int64(0)
+	timeDurationOne := time.Duration(1)
+	uintOne := uint64(1)
+	intOne := int64(1)
+
+	resultZero := float64(0)
+	resultOne := float64(1)
+
+	assert.Equal(t, divideOrReturnZero(timeDurationOne, timeDurationZero), resultZero)
+	assert.Equal(t, divideOrReturnZero(timeDurationOne, unitZero), resultZero)
+	assert.Equal(t, divideOrReturnZero(timeDurationOne, intZero), resultZero)
+	assert.Equal(t, divideOrReturnZero(timeDurationOne, timeDurationOne), resultOne)
+	assert.Equal(t, divideOrReturnZero(timeDurationOne, uintOne), resultOne)
+	assert.Equal(t, divideOrReturnZero(timeDurationOne, intOne), resultOne)
+	assert.Equal(t, divideOrReturnZero(uintOne, timeDurationOne), resultOne)
+	assert.Equal(t, divideOrReturnZero(uintOne, uintOne), resultOne)
+	assert.Equal(t, divideOrReturnZero(uintOne, intOne), resultOne)
+	assert.Equal(t, divideOrReturnZero(intOne, timeDurationOne), resultOne)
+	assert.Equal(t, divideOrReturnZero(intOne, uintOne), resultOne)
+	assert.Equal(t, divideOrReturnZero(intOne, intOne), resultOne)
+
+	// Unexpected type
+	int16 := int16(1)
+	intArray := [2]int64{1, 2}
+
+	assert.Equal(t, divideOrReturnZero(uintOne, int16), resultZero)
+	assert.Equal(t, divideOrReturnZero(uintOne, intArray), resultZero)
+
+}