sql/telemetry: add sync.Pool for SampledQuery objects

Add a pool for SampledQuery objects. At high logging frequencies
we can avoid an allocation per statement.

Epic: none

Release note: None

pkg/sql/exec_log.go

@@ -355,7 +355,10 @@ func (p *planner) maybeLogStatementInternal(
 			})
 		}
 
-		sampledQuery := eventpb.SampledQuery{
+		sampledQuery := getSampledQuery()
+		defer releaseSampledQuery(sampledQuery)
+
+		*sampledQuery = eventpb.SampledQuery{
 			CommonSQLExecDetails:                  execDetails,
 			SkippedQueries:                        skippedQueries,
 			CostEstimate:                          p.curPlan.instrumentation.costEstimate,
@@ -431,7 +434,7 @@ func (p *planner) maybeLogStatementInternal(
 			SchemaChangerMode:                     p.curPlan.instrumentation.schemaChangerMode.String(),
 		}
 
-		p.logOperationalEventsOnlyExternally(ctx, &sampledQuery)
+		p.logOperationalEventsOnlyExternally(ctx, sampledQuery)
 	}
 }
 

pkg/sql/telemetry_logging.go

@@ -11,12 +11,14 @@
 package sql
 
 import (
+	"sync"
 	"sync/atomic"
 	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/settings"
 	"github.com/cockroachdb/cockroach/pkg/settings/cluster"
 	"github.com/cockroachdb/cockroach/pkg/sql/execstats"
+	"github.com/cockroachdb/cockroach/pkg/util/log/eventpb"
 	"github.com/cockroachdb/cockroach/pkg/util/syncutil"
 	"github.com/cockroachdb/cockroach/pkg/util/timeutil"
 	"github.com/cockroachdb/cockroach/pkg/util/tracing"
@@ -96,6 +98,23 @@ var telemetrySamplingMode = settings.RegisterEnumSetting(
 	settings.WithPublic,
 )
 
+// SampledQuery objects are short-lived but can be
+// allocated frequently if logging frequency is high.
+var sampledQueryPool = sync.Pool{
+	New: func() interface{} {
+		return new(eventpb.SampledQuery)
+	},
+}
+
+func getSampledQuery() *eventpb.SampledQuery {
+	return sampledQueryPool.Get().(*eventpb.SampledQuery)
+}
+
+func releaseSampledQuery(sq *eventpb.SampledQuery) {
+	*sq = eventpb.SampledQuery{}
+	sampledQueryPool.Put(sq)
+}
+
 // TelemetryLoggingMetrics keeps track of the last time at which an event
 // was sampled to the telemetry channel, and the number of skipped events
 // since the last sampled event.