Handle new pg_stat_statements column names (#874)

Update pg_stat_statements collector to handle the new column names in
PostgreSQL 13.

Fixes: https://github.com/prometheus-community/postgres_exporter/issues/502

Signed-off-by: SuperQ <superq@gmail.com>

collector/pg_stat_statements.go

@@ -17,6 +17,7 @@ import (
 	"context"
 	"database/sql"
 
+	"github.com/blang/semver/v4"
 	"github.com/go-kit/log"
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -90,12 +91,37 @@ var (
 		)
 	ORDER BY seconds_total DESC
 	LIMIT 100;`
+
+	pgStatStatementsNewQuery = `SELECT
+		pg_get_userbyid(userid) as user,
+		pg_database.datname,
+		pg_stat_statements.queryid,
+		pg_stat_statements.calls as calls_total,
+		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
+		FROM pg_stat_statements
+	JOIN pg_database
+		ON pg_database.oid = pg_stat_statements.dbid
+	WHERE
+		total_time > (
+		SELECT percentile_cont(0.1)
+			WITHIN GROUP (ORDER BY total_time)
+			FROM pg_stat_statements
+		)
+	ORDER BY seconds_total DESC
+	LIMIT 100;`
 )
 
 func (PGStatStatementsCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	query := pgStatStatementsQuery
+	if instance.version.GE(semver.MustParse("13.0.0")) {
+		query = pgStatStatementsNewQuery
+	}
+
 	db := instance.getDB()
-	rows, err := db.QueryContext(ctx,
-		pgStatStatementsQuery)
+	rows, err := db.QueryContext(ctx, query)
 
 	if err != nil {
 		return err

collector/pg_stat_statements_test.go

@@ -17,6 +17,7 @@ import (
 	"testing"
 
 	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/blang/semver/v4"
 	"github.com/prometheus/client_golang/prometheus"
 	dto "github.com/prometheus/client_model/go"
 	"github.com/smartystreets/goconvey/convey"
@@ -29,7 +30,7 @@ func TestPGStateStatementsCollector(t *testing.T) {
 	}
 	defer db.Close()
 
-	inst := &instance{db: db}
+	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"}
 	rows := sqlmock.NewRows(columns).
@@ -72,12 +73,12 @@ func TestPGStateStatementsCollectorNull(t *testing.T) {
 	}
 	defer db.Close()
 
-	inst := &instance{db: db}
+	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"}
 	rows := sqlmock.NewRows(columns).
 		AddRow(nil, nil, nil, nil, nil, nil, nil, nil)
-	mock.ExpectQuery(sanitizeQuery(pgStatStatementsQuery)).WillReturnRows(rows)
+	mock.ExpectQuery(sanitizeQuery(pgStatStatementsNewQuery)).WillReturnRows(rows)
 
 	ch := make(chan prometheus.Metric)
 	go func() {
@@ -107,3 +108,46 @@ func TestPGStateStatementsCollectorNull(t *testing.T) {
 		t.Errorf("there were unfulfilled exceptions: %s", err)
 	}
 }
+
+func TestPGStateStatementsCollectorNewPG(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Error opening a stub db connection: %s", err)
+	}
+	defer db.Close()
+
+	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"}
+	rows := sqlmock.NewRows(columns).
+		AddRow("postgres", "postgres", 1500, 5, 0.4, 100, 0.1, 0.2)
+	mock.ExpectQuery(sanitizeQuery(pgStatStatementsNewQuery)).WillReturnRows(rows)
+
+	ch := make(chan prometheus.Metric)
+	go func() {
+		defer close(ch)
+		c := PGStatStatementsCollector{}
+
+		if err := c.Update(context.Background(), inst, ch); err != nil {
+			t.Errorf("Error calling PGStatStatementsCollector.Update: %s", err)
+		}
+	}()
+
+	expected := []MetricResult{
+		{labels: labelMap{"user": "postgres", "datname": "postgres", "queryid": "1500"}, metricType: dto.MetricType_COUNTER, value: 5},
+		{labels: labelMap{"user": "postgres", "datname": "postgres", "queryid": "1500"}, metricType: dto.MetricType_COUNTER, value: 0.4},
+		{labels: labelMap{"user": "postgres", "datname": "postgres", "queryid": "1500"}, metricType: dto.MetricType_COUNTER, value: 100},
+		{labels: labelMap{"user": "postgres", "datname": "postgres", "queryid": "1500"}, metricType: dto.MetricType_COUNTER, value: 0.1},
+		{labels: labelMap{"user": "postgres", "datname": "postgres", "queryid": "1500"}, metricType: dto.MetricType_COUNTER, value: 0.2},
+	}
+
+	convey.Convey("Metrics comparison", t, func() {
+		for _, expect := range expected {
+			m := readMetric(<-ch)
+			convey.So(expect, convey.ShouldResemble, m)
+		}
+	})
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("there were unfulfilled exceptions: %s", err)
+	}
+}