Add max, mean, and stddev timing metrics to stat_statements collector

- Add postgres_stat_statements_max_seconds metric for maximum execution time
- Add postgres_stat_statements_mean_seconds metric for average execution time
- Add postgres_stat_statements_stddev_seconds metric for execution time variance
- Support all PostgreSQL versions with appropriate column names
- Update test cases to include new metrics

Signed-off-by: Irfan Habib <[email protected]>

Author: irfanhabib

collector/pg_stat_statements.go

@@ -94,6 +94,24 @@ var (
 		[]string{"user", "datname", "queryid"},
 		prometheus.Labels{},
 	)
+	statStatementsMaxSeconds = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statStatementsSubsystem, "max_seconds"),
+		"Maximum time spent in a single execution of the statement, in seconds",
+		[]string{"user", "datname", "queryid"},
+		prometheus.Labels{},
+	)
+	statStatementsMeanSeconds = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statStatementsSubsystem, "mean_seconds"),
+		"Mean time spent per execution of the statement, in seconds",
+		[]string{"user", "datname", "queryid"},
+		prometheus.Labels{},
+	)
+	statStatementsStddevSeconds = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statStatementsSubsystem, "stddev_seconds"),
+		"Standard deviation of time spent in the statement, in seconds",
+		[]string{"user", "datname", "queryid"},
+		prometheus.Labels{},
+	)
 
 	statStatementsQuery = prometheus.NewDesc(
 		prometheus.BuildFQName(namespace, statStatementsSubsystem, "query_id"),
@@ -115,7 +133,10 @@ const (
 		pg_stat_statements.total_time / 1000.0 as seconds_total,
 		pg_stat_statements.rows as rows_total,
 		pg_stat_statements.blk_read_time / 1000.0 as block_read_seconds_total,
-		pg_stat_statements.blk_write_time / 1000.0 as block_write_seconds_total
+		pg_stat_statements.blk_write_time / 1000.0 as block_write_seconds_total,
+		pg_stat_statements.max_time / 1000.0 as max_seconds,
+		pg_stat_statements.mean_time / 1000.0 as mean_seconds,
+		pg_stat_statements.stddev_time / 1000.0 as stddev_seconds
 		FROM pg_stat_statements
 	JOIN pg_database
 		ON pg_database.oid = pg_stat_statements.dbid
@@ -137,7 +158,10 @@ const (
 		pg_stat_statements.total_exec_time / 1000.0 as seconds_total,
 		pg_stat_statements.rows as rows_total,
 		pg_stat_statements.blk_read_time / 1000.0 as block_read_seconds_total,
-		pg_stat_statements.blk_write_time / 1000.0 as block_write_seconds_total
+		pg_stat_statements.blk_write_time / 1000.0 as block_write_seconds_total,
+		pg_stat_statements.max_exec_time / 1000.0 as max_seconds,
+		pg_stat_statements.mean_exec_time / 1000.0 as mean_seconds,
+		pg_stat_statements.stddev_exec_time / 1000.0 as stddev_seconds
 		FROM pg_stat_statements
 	JOIN pg_database
 		ON pg_database.oid = pg_stat_statements.dbid
@@ -159,7 +183,10 @@ const (
 		pg_stat_statements.total_exec_time / 1000.0 as seconds_total,
 		pg_stat_statements.rows as rows_total,
 		pg_stat_statements.shared_blk_read_time / 1000.0 as block_read_seconds_total,
-		pg_stat_statements.shared_blk_write_time / 1000.0 as block_write_seconds_total
+		pg_stat_statements.shared_blk_write_time / 1000.0 as block_write_seconds_total,
+		pg_stat_statements.max_exec_time / 1000.0 as max_seconds,
+		pg_stat_statements.mean_exec_time / 1000.0 as mean_seconds,
+		pg_stat_statements.stddev_exec_time / 1000.0 as stddev_seconds
 		FROM pg_stat_statements
 	JOIN pg_database
 		ON pg_database.oid = pg_stat_statements.dbid
@@ -201,12 +228,12 @@ func (c PGStatStatementsCollector) Update(ctx context.Context, instance *instanc
 	for rows.Next() {
 		var user, datname, queryid, statement sql.NullString
 		var callsTotal, rowsTotal sql.NullInt64
-		var secondsTotal, blockReadSecondsTotal, blockWriteSecondsTotal sql.NullFloat64
+		var secondsTotal, blockReadSecondsTotal, blockWriteSecondsTotal, maxSeconds, meanSeconds, stddevSeconds sql.NullFloat64
 		var columns []any
 		if c.includeQueryStatement {
-			columns = []any{&user, &datname, &queryid, &statement, &callsTotal, &secondsTotal, &rowsTotal, &blockReadSecondsTotal, &blockWriteSecondsTotal}
+			columns = []any{&user, &datname, &queryid, &statement, &callsTotal, &secondsTotal, &rowsTotal, &blockReadSecondsTotal, &blockWriteSecondsTotal, &maxSeconds, &meanSeconds, &stddevSeconds}
 		} else {
-			columns = []any{&user, &datname, &queryid, &callsTotal, &secondsTotal, &rowsTotal, &blockReadSecondsTotal, &blockWriteSecondsTotal}
+			columns = []any{&user, &datname, &queryid, &callsTotal, &secondsTotal, &rowsTotal, &blockReadSecondsTotal, &blockWriteSecondsTotal, &maxSeconds, &meanSeconds, &stddevSeconds}
 		}
 		if err := rows.Scan(columns...); err != nil {
 			return err
@@ -280,6 +307,39 @@ func (c PGStatStatementsCollector) Update(ctx context.Context, instance *instanc
 			userLabel, datnameLabel, queryidLabel,
 		)
 
+		maxSecondsMetric := 0.0
+		if maxSeconds.Valid {
+			maxSecondsMetric = maxSeconds.Float64
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statStatementsMaxSeconds,
+			prometheus.GaugeValue,
+			maxSecondsMetric,
+			userLabel, datnameLabel, queryidLabel,
+		)
+
+		meanSecondsMetric := 0.0
+		if meanSeconds.Valid {
+			meanSecondsMetric = meanSeconds.Float64
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statStatementsMeanSeconds,
+			prometheus.GaugeValue,
+			meanSecondsMetric,
+			userLabel, datnameLabel, queryidLabel,
+		)
+
+		stddevSecondsMetric := 0.0
+		if stddevSeconds.Valid {
+			stddevSecondsMetric = stddevSeconds.Float64
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statStatementsStddevSeconds,
+			prometheus.GaugeValue,
+			stddevSecondsMetric,
+			userLabel, datnameLabel, queryidLabel,
+		)
+
 		if c.includeQueryStatement {
 			_, ok := presentQueryIds[queryidLabel]
 			if !ok {

collector/pg_stat_statements_test.go

@@ -33,9 +33,9 @@ func TestPGStateStatementsCollector(t *testing.T) {
 
 	inst := &instance{db: db, version: semver.MustParse("12.0.0")}
 
-	columns := []string{"user", "datname", "queryid", "calls_total", "seconds_total", "rows_total", "block_read_seconds_total", "block_write_seconds_total"}
+	columns := []string{"user", "datname", "queryid", "calls_total", "seconds_total", "rows_total", "block_read_seconds_total", "block_write_seconds_total", "max_seconds", "mean_seconds", "stddev_seconds"}
 	rows := sqlmock.NewRows(columns).
-		AddRow("postgres", "postgres", 1500, 5, 0.4, 100, 0.1, 0.2)
+		AddRow("postgres", "postgres", 1500, 5, 0.4, 100, 0.1, 0.2, 0.8, 0.08, 0.05)
 	mock.ExpectQuery(sanitizeQuery(fmt.Sprintf(pgStatStatementsQuery, ""))).WillReturnRows(rows)
 
 	ch := make(chan prometheus.Metric)
@@ -207,9 +207,9 @@ func TestPGStateStatementsCollectorNewPG(t *testing.T) {
 
 	inst := &instance{db: db, version: semver.MustParse("13.3.7")}
 
-	columns := []string{"user", "datname", "queryid", "calls_total", "seconds_total", "rows_total", "block_read_seconds_total", "block_write_seconds_total"}
+	columns := []string{"user", "datname", "queryid", "calls_total", "seconds_total", "rows_total", "block_read_seconds_total", "block_write_seconds_total", "max_seconds", "mean_seconds", "stddev_seconds"}
 	rows := sqlmock.NewRows(columns).
-		AddRow("postgres", "postgres", 1500, 5, 0.4, 100, 0.1, 0.2)
+		AddRow("postgres", "postgres", 1500, 5, 0.4, 100, 0.1, 0.2, 0.8, 0.08, 0.05)
 	mock.ExpectQuery(sanitizeQuery(fmt.Sprintf(pgStatStatementsNewQuery, ""))).WillReturnRows(rows)
 
 	ch := make(chan prometheus.Metric)
@@ -294,9 +294,9 @@ func TestPGStateStatementsCollector_PG17(t *testing.T) {
 
 	inst := &instance{db: db, version: semver.MustParse("17.0.0")}
 
-	columns := []string{"user", "datname", "queryid", "calls_total", "seconds_total", "rows_total", "block_read_seconds_total", "block_write_seconds_total"}
+	columns := []string{"user", "datname", "queryid", "calls_total", "seconds_total", "rows_total", "block_read_seconds_total", "block_write_seconds_total", "max_seconds", "mean_seconds", "stddev_seconds"}
 	rows := sqlmock.NewRows(columns).
-		AddRow("postgres", "postgres", 1500, 5, 0.4, 100, 0.1, 0.2)
+		AddRow("postgres", "postgres", 1500, 5, 0.4, 100, 0.1, 0.2, 0.8, 0.08, 0.05)
 	mock.ExpectQuery(sanitizeQuery(fmt.Sprintf(pgStatStatementsQuery_PG17, ""))).WillReturnRows(rows)
 
 	ch := make(chan prometheus.Metric)