From d417e14fc42524bc534d9b26b4a47ec2496af7f7 Mon Sep 17 00:00:00 2001
From: Nurlan Moldomurov <bupychuk1989@gmail.com>
Date: Tue, 26 Nov 2024 13:26:44 +0300
Subject: [PATCH] PMM-13448 Support PG17 to provide pre PG17 metrics support.

---
 collector/pg_stat_bgwriter.go      | 53 +++++++++++++++++++++++++-----
 collector/pg_stat_bgwriter_test.go |  4 +--
 2 files changed, 46 insertions(+), 11 deletions(-)

diff --git a/collector/pg_stat_bgwriter.go b/collector/pg_stat_bgwriter.go
index febea0886..0b73b4f44 100644
--- a/collector/pg_stat_bgwriter.go
+++ b/collector/pg_stat_bgwriter.go
@@ -16,7 +16,7 @@ package collector
 import (
 	"context"
 	"database/sql"
-
+	"github.com/blang/semver/v4"
 	"github.com/prometheus/client_golang/prometheus"
 )
 
@@ -170,7 +170,7 @@ var statBGWriter = map[string]*prometheus.Desc{
 	),
 }
 
-const statBGWriterQuery = `SELECT
+const statBGWriterQueryPrePG17 = `SELECT
 		checkpoints_timed
 		,checkpoints_req
 		,checkpoint_write_time
@@ -184,19 +184,55 @@ const statBGWriterQuery = `SELECT
 		,stats_reset
 	FROM pg_stat_bgwriter;`
 
-func (PGStatBGWriterCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+const statBGWriterQueryPost17 = `SELECT
+		buffers_clean
+		,maxwritten_clean
+		,buffers_alloc
+		,stats_reset
+	FROM pg_stat_bgwriter;`
+
+const statCheckpointerQuery = `SELECT
+		num_timed
+		,num_requested
+		,restartpoints_timed
+		,restartpoints_req
+		,restartpoints_done
+		,write_time
+		,sync_time
+		,buffers_written
+		,stats_reset
+	FROM pg_stat_checkpointer;`
 
+func (p PGStatBGWriterCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
 	db := instance.getDB()
-	row := db.QueryRowContext(ctx,
-		statBGWriterQuery)
 
 	var cpt, cpr, bcp, bc, mwc, bb, bbf, ba sql.NullInt64
 	var cpwt, cpst sql.NullFloat64
 	var sr sql.NullTime
 
-	err := row.Scan(&cpt, &cpr, &cpwt, &cpst, &bcp, &bc, &mwc, &bb, &bbf, &ba, &sr)
-	if err != nil {
-		return err
+	if instance.version.GE(semver.MustParse("17.0.0")) {
+		row := db.QueryRowContext(ctx,
+			statBGWriterQueryPost17)
+		err := row.Scan(&bc, &mwc, &ba, &sr)
+		if err != nil {
+			return err
+		}
+		var rpt, rpr, rpd sql.NullInt64
+		var csr sql.NullTime
+		// these variables are not used, but I left them here for reference
+		row = db.QueryRowContext(ctx,
+			statCheckpointerQuery)
+		err = row.Scan(&cpt, &cpr, &rpt, &rpr, &rpd, &cpwt, &cpst, &bcp, &csr)
+		if err != nil {
+			return err
+		}
+	} else {
+		row := db.QueryRowContext(ctx,
+			statBGWriterQueryPrePG17)
+		err := row.Scan(&cpt, &cpr, &cpwt, &cpst, &bcp, &bc, &mwc, &bb, &bbf, &ba, &sr)
+		if err != nil {
+			return err
+		}
 	}
 
 	cptMetric := 0.0
@@ -400,6 +436,5 @@ func (PGStatBGWriterCollector) Update(ctx context.Context, instance *instance, c
 		"exporter",
 		instance.name,
 	)
-
 	return nil
 }
diff --git a/collector/pg_stat_bgwriter_test.go b/collector/pg_stat_bgwriter_test.go
index c229cee39..6d137b06f 100644
--- a/collector/pg_stat_bgwriter_test.go
+++ b/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(statBGWriterQueryPrePG17)).WillReturnRows(rows)
 
 	ch := make(chan prometheus.Metric)
 	go func() {
@@ -114,7 +114,7 @@ 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(statBGWriterQueryPrePG17)).WillReturnRows(rows)
 
 	ch := make(chan prometheus.Metric)
 	go func() {