Checkpoint related columns in PG 17 have been moved from pg_stat_bgwr…

…iter to pg_stat_checkpointer

Fix prometheus-community#1060

See: https://www.dbi-services.com/blog/postgresql-17-new-catalog-view-pg_stat_checkpointer/

collector/pg_stat_bgwriter.go

@@ -17,6 +17,7 @@ import (
 	"context"
 	"database/sql"
 
+	"github.com/blang/semver/v4"
 	"github.com/prometheus/client_golang/prometheus"
 )
 
@@ -101,7 +102,7 @@ var (
 		prometheus.Labels{},
 	)
 
-	statBGWriterQuery = `SELECT
+	statBGWriterQueryBefore17 = `SELECT
 		checkpoints_timed
 		,checkpoints_req
 		,checkpoint_write_time
@@ -114,12 +115,23 @@ var (
 		,buffers_alloc
 		,stats_reset
 	FROM pg_stat_bgwriter;`
+
+	statBGWriterQueryAfter17 = `SELECT
+		buffers_clean
+		,maxwritten_clean
+		,buffers_alloc
+		,stats_reset
+	FROM pg_stat_bgwriter;`
 )
 
 func (PGStatBGWriterCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	query := statBGWriterQueryBefore17
+	if instance.version.GE(semver.MustParse("17.0.0")) {
+		query = statBGWriterQueryAfter17
+	}
+
 	db := instance.getDB()
-	row := db.QueryRowContext(ctx,
-		statBGWriterQuery)
+	row := db.QueryRowContext(ctx, query)
 
 	var cpt, cpr, bcp, bc, mwc, bb, bbf, ba sql.NullInt64
 	var cpwt, cpst sql.NullFloat64

collector/pg_stat_bgwriter_test.go

@@ -52,7 +52,7 @@ func TestPGStatBGWriterCollector(t *testing.T) {
 
 	rows := sqlmock.NewRows(columns).
 		AddRow(354, 4945, 289097744, 1242257, int64(3275602074), 89320867, 450139, 2034563757, 0, int64(2725688749), srT)
-	mock.ExpectQuery(sanitizeQuery(statBGWriterQuery)).WillReturnRows(rows)
+	mock.ExpectQuery(sanitizeQuery(statBGWriterQueryBefore17)).WillReturnRows(rows)
 
 	ch := make(chan prometheus.Metric)
 	go func() {
@@ -113,7 +113,7 @@ func TestPGStatBGWriterCollectorNullValues(t *testing.T) {
 
 	rows := sqlmock.NewRows(columns).
 		AddRow(nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil)
-	mock.ExpectQuery(sanitizeQuery(statBGWriterQuery)).WillReturnRows(rows)
+	mock.ExpectQuery(sanitizeQuery(statBGWriterQueryBefore17)).WillReturnRows(rows)
 
 	ch := make(chan prometheus.Metric)
 	go func() {