telemetry: fix the integer quantization

pkg/server/telemetry/features.go

@@ -12,6 +12,7 @@ package telemetry
 
 import (
 	"fmt"
+	"math"
 	"sync/atomic"
 
 	"github.com/cockroachdb/cockroach/pkg/sql/pgwire/pgcode"
@@ -27,16 +28,22 @@ import (
 // raw numbers.
 // The numbers 0-10 are reported unchanged.
 func Bucket10(num int64) int64 {
-	if num <= 0 {
-		return 0
+	if num == math.MinInt64 {
+		// This is needed to prevent overflow in the negation below.
+		return -1000000000000000000
+	}
+	sign := int64(1)
+	if num < 0 {
+		sign = -1
+		num = -num
 	}
 	if num < 10 {
-		return num
+		return num * sign
 	}
 	res := int64(10)
-	for ; res < 1000000000000000000 && res*10 < num; res *= 10 {
+	for ; res < 1000000000000000000 && res*10 <= num; res *= 10 {
 	}
-	return res
+	return res * sign
 }
 
 // CountBucketed counts the feature identified by prefix and the value, using

pkg/server/telemetry/features_test.go

@@ -11,6 +11,7 @@
 package telemetry_test
 
 import (
+	"math"
 	"sync"
 	"testing"
 
@@ -40,3 +41,53 @@ func TestGetCounterDoesNotRace(t *testing.T) {
 	}
 	require.Len(t, counterSet, 1)
 }
+
+// TestBucket checks integer quantization.
+func TestBucket(t *testing.T) {
+	testData := []struct {
+		input    int64
+		expected int64
+	}{
+		{0, 0},
+		{1, 1},
+		{2, 2},
+		{3, 3},
+		{4, 4},
+		{5, 5},
+		{6, 6},
+		{7, 7},
+		{8, 8},
+		{9, 9},
+		{10, 10},
+		{11, 10},
+		{20, 10},
+		{99, 10},
+		{100, 100},
+		{101, 100},
+		{200, 100},
+		{999, 100},
+		{1000, 1000},
+		{math.MaxInt64, 1000000000000000000},
+		{-1, -1},
+		{-2, -2},
+		{-3, -3},
+		{-4, -4},
+		{-5, -5},
+		{-6, -6},
+		{-7, -7},
+		{-8, -8},
+		{-9, -9},
+		{-10, -10},
+		{-11, -10},
+		{-20, -10},
+		{-100, -100},
+		{-200, -100},
+		{math.MinInt64, -1000000000000000000},
+	}
+
+	for _, tc := range testData {
+		if actual, expected := telemetry.Bucket10(tc.input), tc.expected; actual != expected {
+			t.Errorf("%d: expected %d, got %d", tc.input, expected, actual)
+		}
+	}
+}