sql: don't allocate phaseTimes on each call to sqlStatsCollector.reset

This allocation was responsible for **0.28%** of a CPU profile when running
Sysbench's oltp_point_select workload.

This was broken in ee48ea7.

Release justification: Reverts perf regression due to newly introduced memory
allocations.

Release note: None

pkg/sql/conn_executor.go

@@ -1635,7 +1635,7 @@ func (ex *connExecutor) execCopyIn(
 			// going through the state machine.
 			ex.state.sqlTimestamp = txnTS
 			ex.statsCollector = ex.newStatsCollector()
-			ex.statsCollector.reset(&ex.server.sqlStats, ex.appStats, ex.phaseTimes)
+			ex.statsCollector.reset(&ex.server.sqlStats, ex.appStats, &ex.phaseTimes)
 			ex.initPlanner(ctx, p)
 			ex.resetPlanner(ctx, p, txn, stmtTS, 0 /* numAnnotations */)
 		},
@@ -2079,7 +2079,7 @@ func (ex *connExecutor) recordError(ctx context.Context, err error) {
 // newStatsCollector returns a sqlStatsCollector that will record stats in the
 // session's stats containers.
 func (ex *connExecutor) newStatsCollector() *sqlStatsCollector {
-	return newSQLStatsCollector(&ex.server.sqlStats, ex.appStats, ex.phaseTimes)
+	return newSQLStatsCollector(&ex.server.sqlStats, ex.appStats, &ex.phaseTimes)
 }
 
 // cancelQuery is part of the registrySession interface.

pkg/sql/conn_executor_exec.go

@@ -362,7 +362,7 @@ func (ex *connExecutor) execStmtInOpenState(
 
 	p := &ex.planner
 	stmtTS := ex.server.cfg.Clock.PhysicalTime()
-	ex.statsCollector.reset(&ex.server.sqlStats, ex.appStats, ex.phaseTimes)
+	ex.statsCollector.reset(&ex.server.sqlStats, ex.appStats, &ex.phaseTimes)
 	ex.resetPlanner(ctx, p, ex.state.mu.txn, stmtTS, stmt.NumAnnotations)
 
 	if os.ImplicitTxn.Get() {
@@ -863,7 +863,7 @@ func (ex *connExecutor) beginTransactionTimestampsAndReadMode(
 		rwMode = ex.readWriteModeWithSessionDefault(s.Modes.ReadWriteMode)
 		return rwMode, now.GoTime(), nil, nil
 	}
-	ex.statsCollector.reset(&ex.server.sqlStats, ex.appStats, ex.phaseTimes)
+	ex.statsCollector.reset(&ex.server.sqlStats, ex.appStats, &ex.phaseTimes)
 	p := &ex.planner
 	ex.resetPlanner(ctx, p, nil /* txn */, now.GoTime(), 0 /* numAnnotations */)
 	ts, err := p.EvalAsOfTimestamp(s.Modes.AsOf)
@@ -1300,7 +1300,7 @@ func (ex *connExecutor) recordTransactionStart() func(txnEvent) {
 }
 
 func (ex *connExecutor) recordTransaction(ev txnEvent, implicit bool) {
-	phaseTimes := ex.statsCollector.phaseTimes
+	phaseTimes := &ex.statsCollector.phaseTimes
 	phaseTimes[transactionEnd] = timeutil.Now()
 	txnStart := phaseTimes[transactionStart]
 	txnEnd := phaseTimes[transactionEnd]

pkg/sql/conn_executor_prepare.go

@@ -152,7 +152,7 @@ func (ex *connExecutor) prepare(
 	// anything other than getting a timestamp.
 	txn := client.NewTxn(ctx, ex.server.cfg.DB, ex.server.cfg.NodeID.Get(), client.RootTxn)
 
-	ex.statsCollector.reset(&ex.server.sqlStats, ex.appStats, ex.phaseTimes)
+	ex.statsCollector.reset(&ex.server.sqlStats, ex.appStats, &ex.phaseTimes)
 	p := &ex.planner
 	ex.resetPlanner(ctx, p, txn, ex.server.cfg.Clock.PhysicalTime() /* stmtTS */, stmt.NumAnnotations)
 	p.stmt = &stmt

pkg/sql/exec_util.go

@@ -1875,18 +1875,18 @@ type sqlStatsCollector struct {
 	// into sqlStats set as the session's current app.
 	appStats *appStats
 	// phaseTimes tracks session-level phase times.
-	phaseTimes *phaseTimes
+	phaseTimes phaseTimes
 }
 
 // newSQLStatsCollector creates an instance of sqlStatsCollector. Note that
 // phaseTimes is an array, not a slice, so this performs a copy-by-value.
 func newSQLStatsCollector(
-	sqlStats *sqlStats, appStats *appStats, phaseTimes phaseTimes,
+	sqlStats *sqlStats, appStats *appStats, phaseTimes *phaseTimes,
 ) *sqlStatsCollector {
 	return &sqlStatsCollector{
 		sqlStats:   sqlStats,
 		appStats:   appStats,
-		phaseTimes: &phaseTimes,
+		phaseTimes: *phaseTimes,
 	}
 }
 
@@ -1914,10 +1914,10 @@ func (s *sqlStatsCollector) recordTransaction(txnTimeSec float64, ev txnEvent, i
 	s.appStats.recordTransaction(txnTimeSec, ev, implicit)
 }
 
-func (s *sqlStatsCollector) reset(sqlStats *sqlStats, appStats *appStats, phaseTimes phaseTimes) {
+func (s *sqlStatsCollector) reset(sqlStats *sqlStats, appStats *appStats, phaseTimes *phaseTimes) {
 	*s = sqlStatsCollector{
 		sqlStats:   sqlStats,
 		appStats:   appStats,
-		phaseTimes: &phaseTimes,
+		phaseTimes: *phaseTimes,
 	}
 }

pkg/sql/executor_statement_metrics.go

@@ -128,7 +128,7 @@ func (ex *connExecutor) recordStatementSummary(
 	bytesRead int64,
 	rowsRead int64,
 ) {
-	phaseTimes := ex.statsCollector.phaseTimes
+	phaseTimes := &ex.statsCollector.phaseTimes
 
 	// Compute the run latency. This is always recorded in the
 	// server metrics.