Switch per-step stats to serialize ints

Per Julien's feedback on #10369, we're choosing to be consistent with
data types inside the stats structure (ints) rather than with the points
format that is part of the normal query responses (strings). We have
this option because this data cannot be NaN/Inf.

Signed-off-by: Andrew Bloomgarden <blmgrdn@amazon.com>

util/stats/query_stats.go

@@ -17,7 +17,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"strconv"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"go.opentelemetry.io/otel"
@@ -81,18 +80,16 @@ func (s QueryTiming) SpanOperation() string {
 // stepStat represents a single statistic for a given step timestamp.
 type stepStat struct {
 	T int64
-	V float64
+	V int64
 }
 
 func (s stepStat) String() string {
-	v := strconv.FormatFloat(s.V, 'f', -1, 64)
-	return fmt.Sprintf("%v @[%v]", v, s.T)
+	return fmt.Sprintf("%v @[%v]", s.V, s.T)
 }
 
 // MarshalJSON implements json.Marshaler.
 func (s stepStat) MarshalJSON() ([]byte, error) {
-	v := strconv.FormatFloat(s.V, 'f', -1, 64)
-	return json.Marshal([...]interface{}{float64(s.T) / 1000, v})
+	return json.Marshal([...]interface{}{float64(s.T) / 1000, s.V})
 }
 
 // queryTimings with all query timers mapped to durations.
@@ -185,7 +182,7 @@ func (qs *QuerySamples) totalSamplesPerStepPoints() []stepStat {
 
 	ts := make([]stepStat, len(qs.TotalSamplesPerStep))
 	for i, c := range qs.TotalSamplesPerStep {
-		ts[i] = stepStat{T: qs.startTimestamp + int64(i)*qs.interval, V: float64(c)}
+		ts[i] = stepStat{T: qs.startTimestamp + int64(i)*qs.interval, V: int64(c)}
 	}
 	return ts
 }

util/stats/stats_test.go

@@ -61,7 +61,7 @@ func TestQueryStatsWithTimersAndSamples(t *testing.T) {
 	require.True(t, match, "Expected timings with one non-zero entry.")
 
 	require.Regexpf(t, `[,{]"totalQueryableSamples":10[,}]`, string(actual), "expected totalQueryableSamples")
-	require.Regexpf(t, `[,{]"totalQueryableSamplesPerStep":\[\[20001,"5"\],\[21001,"0"\],\[22001,"0"\],\[23001,"0"\],\[24001,"0"\],\[25001,"5"\]\]`, string(actual), "expected totalQueryableSamplesPerStep")
+	require.Regexpf(t, `[,{]"totalQueryableSamplesPerStep":\[\[20001,5\],\[21001,0\],\[22001,0\],\[23001,0\],\[24001,0\],\[25001,5\]\]`, string(actual), "expected totalQueryableSamplesPerStep")
 }
 
 func TestQueryStatsWithSpanTimers(t *testing.T) {