Checkpoint related columns in PG 17 have been moved from pg_stat_bgwriter to pg_stat_checkpointer (#1072)

* Checkpoint related columns in PG 17 have been moved from pg_stat_bgwriter to pg_stat_checkpointer Fix https://github.com/prometheus-community/postgres_exporter/issues/1060 See: https://www.dbi-services.com/blog/postgresql-17-new-catalog-view-pg_stat_checkpointer/ Signed-off-by: Nicolas Rodriguez <nico@nicoladmin.fr> * Add support for pg_stat_checkpointer See: https://www.dbi-services.com/blog/postgresql-17-new-catalog-view-pg_stat_checkpointer/ Signed-off-by: Nicolas Rodriguez <nico@nicoladmin.fr> * Run integration tests with Postgres 17 Signed-off-by: Nicolas Rodriguez <nico@nicoladmin.fr> * Update date in file header Signed-off-by: Nicolas Rodriguez <nico@nicoladmin.fr> --------- Signed-off-by: Nicolas Rodriguez <nico@nicoladmin.fr>
2025-04-11 03:31:26 +00:00 · 2025-01-01 22:03:43 +01:00 · 2025-01-01 22:03:43 +01:00 · bea2609519
commit bea2609519
parent 5145620988
5 changed files with 533 additions and 111 deletions
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@ -63,6 +63,7 @@ workflows:
            - cimg/postgres:14.9
            - cimg/postgres:15.4
            - cimg/postgres:16.0
+            - cimg/postgres:17.0
    - prometheus/build:
        name: build
        parallelism: 3
--- a/collector/pg_stat_bgwriter.go
+++ b/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
@ -114,121 +115,177 @@ 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 {
-	db := instance.getDB()
-	row := db.QueryRowContext(ctx,
-		statBGWriterQuery)
+	if instance.version.GE(semver.MustParse("17.0.0")) {
+		db := instance.getDB()
+		row := db.QueryRowContext(ctx, statBGWriterQueryAfter17)

-	var cpt, cpr, bcp, bc, mwc, bb, bbf, ba sql.NullInt64
-	var cpwt, cpst sql.NullFloat64
-	var sr sql.NullTime
+		var bc, mwc, ba sql.NullInt64
+		var sr sql.NullTime

-	err := row.Scan(&cpt, &cpr, &cpwt, &cpst, &bcp, &bc, &mwc, &bb, &bbf, &ba, &sr)
-	if err != nil {
-		return err
-	}
+		err := row.Scan(&bc, &mwc, &ba, &sr)
+		if err != nil {
+			return err
+		}

-	cptMetric := 0.0
-	if cpt.Valid {
-		cptMetric = float64(cpt.Int64)
+		bcMetric := 0.0
+		if bc.Valid {
+			bcMetric = float64(bc.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterBuffersCleanDesc,
+			prometheus.CounterValue,
+			bcMetric,
+		)
+		mwcMetric := 0.0
+		if mwc.Valid {
+			mwcMetric = float64(mwc.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterMaxwrittenCleanDesc,
+			prometheus.CounterValue,
+			mwcMetric,
+		)
+		baMetric := 0.0
+		if ba.Valid {
+			baMetric = float64(ba.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterBuffersAllocDesc,
+			prometheus.CounterValue,
+			baMetric,
+		)
+		srMetric := 0.0
+		if sr.Valid {
+			srMetric = float64(sr.Time.Unix())
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterStatsResetDesc,
+			prometheus.CounterValue,
+			srMetric,
+		)
+	} else {
+		db := instance.getDB()
+		row := db.QueryRowContext(ctx, statBGWriterQueryBefore17)
+
+		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
+		}
+
+		cptMetric := 0.0
+		if cpt.Valid {
+			cptMetric = float64(cpt.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterCheckpointsTimedDesc,
+			prometheus.CounterValue,
+			cptMetric,
+		)
+		cprMetric := 0.0
+		if cpr.Valid {
+			cprMetric = float64(cpr.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterCheckpointsReqDesc,
+			prometheus.CounterValue,
+			cprMetric,
+		)
+		cpwtMetric := 0.0
+		if cpwt.Valid {
+			cpwtMetric = float64(cpwt.Float64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterCheckpointsReqTimeDesc,
+			prometheus.CounterValue,
+			cpwtMetric,
+		)
+		cpstMetric := 0.0
+		if cpst.Valid {
+			cpstMetric = float64(cpst.Float64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterCheckpointsSyncTimeDesc,
+			prometheus.CounterValue,
+			cpstMetric,
+		)
+		bcpMetric := 0.0
+		if bcp.Valid {
+			bcpMetric = float64(bcp.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterBuffersCheckpointDesc,
+			prometheus.CounterValue,
+			bcpMetric,
+		)
+		bcMetric := 0.0
+		if bc.Valid {
+			bcMetric = float64(bc.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterBuffersCleanDesc,
+			prometheus.CounterValue,
+			bcMetric,
+		)
+		mwcMetric := 0.0
+		if mwc.Valid {
+			mwcMetric = float64(mwc.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterMaxwrittenCleanDesc,
+			prometheus.CounterValue,
+			mwcMetric,
+		)
+		bbMetric := 0.0
+		if bb.Valid {
+			bbMetric = float64(bb.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterBuffersBackendDesc,
+			prometheus.CounterValue,
+			bbMetric,
+		)
+		bbfMetric := 0.0
+		if bbf.Valid {
+			bbfMetric = float64(bbf.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterBuffersBackendFsyncDesc,
+			prometheus.CounterValue,
+			bbfMetric,
+		)
+		baMetric := 0.0
+		if ba.Valid {
+			baMetric = float64(ba.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterBuffersAllocDesc,
+			prometheus.CounterValue,
+			baMetric,
+		)
+		srMetric := 0.0
+		if sr.Valid {
+			srMetric = float64(sr.Time.Unix())
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statBGWriterStatsResetDesc,
+			prometheus.CounterValue,
+			srMetric,
+		)
 	}
-	ch <- prometheus.MustNewConstMetric(
-		statBGWriterCheckpointsTimedDesc,
-		prometheus.CounterValue,
-		cptMetric,
-	)
-	cprMetric := 0.0
-	if cpr.Valid {
-		cprMetric = float64(cpr.Int64)
-	}
-	ch <- prometheus.MustNewConstMetric(
-		statBGWriterCheckpointsReqDesc,
-		prometheus.CounterValue,
-		cprMetric,
-	)
-	cpwtMetric := 0.0
-	if cpwt.Valid {
-		cpwtMetric = float64(cpwt.Float64)
-	}
-	ch <- prometheus.MustNewConstMetric(
-		statBGWriterCheckpointsReqTimeDesc,
-		prometheus.CounterValue,
-		cpwtMetric,
-	)
-	cpstMetric := 0.0
-	if cpst.Valid {
-		cpstMetric = float64(cpst.Float64)
-	}
-	ch <- prometheus.MustNewConstMetric(
-		statBGWriterCheckpointsSyncTimeDesc,
-		prometheus.CounterValue,
-		cpstMetric,
-	)
-	bcpMetric := 0.0
-	if bcp.Valid {
-		bcpMetric = float64(bcp.Int64)
-	}
-	ch <- prometheus.MustNewConstMetric(
-		statBGWriterBuffersCheckpointDesc,
-		prometheus.CounterValue,
-		bcpMetric,
-	)
-	bcMetric := 0.0
-	if bc.Valid {
-		bcMetric = float64(bc.Int64)
-	}
-	ch <- prometheus.MustNewConstMetric(
-		statBGWriterBuffersCleanDesc,
-		prometheus.CounterValue,
-		bcMetric,
-	)
-	mwcMetric := 0.0
-	if mwc.Valid {
-		mwcMetric = float64(mwc.Int64)
-	}
-	ch <- prometheus.MustNewConstMetric(
-		statBGWriterMaxwrittenCleanDesc,
-		prometheus.CounterValue,
-		mwcMetric,
-	)
-	bbMetric := 0.0
-	if bb.Valid {
-		bbMetric = float64(bb.Int64)
-	}
-	ch <- prometheus.MustNewConstMetric(
-		statBGWriterBuffersBackendDesc,
-		prometheus.CounterValue,
-		bbMetric,
-	)
-	bbfMetric := 0.0
-	if bbf.Valid {
-		bbfMetric = float64(bbf.Int64)
-	}
-	ch <- prometheus.MustNewConstMetric(
-		statBGWriterBuffersBackendFsyncDesc,
-		prometheus.CounterValue,
-		bbfMetric,
-	)
-	baMetric := 0.0
-	if ba.Valid {
-		baMetric = float64(ba.Int64)
-	}
-	ch <- prometheus.MustNewConstMetric(
-		statBGWriterBuffersAllocDesc,
-		prometheus.CounterValue,
-		baMetric,
-	)
-	srMetric := 0.0
-	if sr.Valid {
-		srMetric = float64(sr.Time.Unix())
-	}
-	ch <- prometheus.MustNewConstMetric(
-		statBGWriterStatsResetDesc,
-		prometheus.CounterValue,
-		srMetric,
-	)

 	return nil
 }
--- 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(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() {
--- a/collector/pg_stat_checkpointer.go
+++ b/collector/pg_stat_checkpointer.go
@ -0,0 +1,221 @@
+// Copyright 2024 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package collector
+
+import (
+	"context"
+	"database/sql"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const statCheckpointerSubsystem = "stat_checkpointer"
+
+func init() {
+	// WARNING:
+	//   Disabled by default because this set of metrics is only available from Postgres 17
+	registerCollector(statCheckpointerSubsystem, defaultDisabled, NewPGStatCheckpointerCollector)
+}
+
+type PGStatCheckpointerCollector struct {
+}
+
+func NewPGStatCheckpointerCollector(collectorConfig) (Collector, error) {
+	return &PGStatCheckpointerCollector{}, nil
+}
+
+var (
+	statCheckpointerNumTimedDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statCheckpointerSubsystem, "num_timed_total"),
+		"Number of scheduled checkpoints due to timeout",
+		[]string{},
+		prometheus.Labels{},
+	)
+	statCheckpointerNumRequestedDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statCheckpointerSubsystem, "num_requested_total"),
+		"Number of requested checkpoints that have been performed",
+		[]string{},
+		prometheus.Labels{},
+	)
+	statCheckpointerRestartpointsTimedDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statCheckpointerSubsystem, "restartpoints_timed_total"),
+		"Number of scheduled restartpoints due to timeout or after a failed attempt to perform it",
+		[]string{},
+		prometheus.Labels{},
+	)
+	statCheckpointerRestartpointsReqDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statCheckpointerSubsystem, "restartpoints_req_total"),
+		"Number of requested restartpoints",
+		[]string{},
+		prometheus.Labels{},
+	)
+	statCheckpointerRestartpointsDoneDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statCheckpointerSubsystem, "restartpoints_done_total"),
+		"Number of restartpoints that have been performed",
+		[]string{},
+		prometheus.Labels{},
+	)
+	statCheckpointerWriteTimeDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statCheckpointerSubsystem, "write_time_total"),
+		"Total amount of time that has been spent in the portion of processing checkpoints and restartpoints where files are written to disk, in milliseconds",
+		[]string{},
+		prometheus.Labels{},
+	)
+	statCheckpointerSyncTimeDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statCheckpointerSubsystem, "sync_time_total"),
+		"Total amount of time that has been spent in the portion of processing checkpoints and restartpoints where files are synchronized to disk, in milliseconds",
+		[]string{},
+		prometheus.Labels{},
+	)
+	statCheckpointerBuffersWrittenDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statCheckpointerSubsystem, "buffers_written_total"),
+		"Number of buffers written during checkpoints and restartpoints",
+		[]string{},
+		prometheus.Labels{},
+	)
+	statCheckpointerStatsResetDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statCheckpointerSubsystem, "stats_reset_total"),
+		"Time at which these statistics were last reset",
+		[]string{},
+		prometheus.Labels{},
+	)
+
+	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 (PGStatCheckpointerCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
+	row := db.QueryRowContext(ctx, statCheckpointerQuery)
+
+	// num_timed           = nt  = bigint
+	// num_requested       = nr  = bigint
+	// restartpoints_timed = rpt = bigint
+	// restartpoints_req   = rpr = bigint
+	// restartpoints_done  = rpd = bigint
+	// write_time          = wt  = double precision
+	// sync_time           = st  = double precision
+	// buffers_written     = bw  = bigint
+	// stats_reset         = sr  = timestamp
+
+	var nt, nr, rpt, rpr, rpd, bw sql.NullInt64
+	var wt, st sql.NullFloat64
+	var sr sql.NullTime
+
+	err := row.Scan(&nt, &nr, &rpt, &rpr, &rpd, &wt, &st, &bw, &sr)
+	if err != nil {
+		return err
+	}
+
+	ntMetric := 0.0
+	if nt.Valid {
+		ntMetric = float64(nt.Int64)
+	}
+	ch <- prometheus.MustNewConstMetric(
+		statCheckpointerNumTimedDesc,
+		prometheus.CounterValue,
+		ntMetric,
+	)
+
+	nrMetric := 0.0
+	if nr.Valid {
+		nrMetric = float64(nr.Int64)
+	}
+	ch <- prometheus.MustNewConstMetric(
+		statCheckpointerNumRequestedDesc,
+		prometheus.CounterValue,
+		nrMetric,
+	)
+
+	rptMetric := 0.0
+	if rpt.Valid {
+		rptMetric = float64(rpt.Int64)
+	}
+	ch <- prometheus.MustNewConstMetric(
+		statCheckpointerRestartpointsTimedDesc,
+		prometheus.CounterValue,
+		rptMetric,
+	)
+
+	rprMetric := 0.0
+	if rpr.Valid {
+		rprMetric = float64(rpr.Int64)
+	}
+	ch <- prometheus.MustNewConstMetric(
+		statCheckpointerRestartpointsReqDesc,
+		prometheus.CounterValue,
+		rprMetric,
+	)
+
+	rpdMetric := 0.0
+	if rpd.Valid {
+		rpdMetric = float64(rpd.Int64)
+	}
+	ch <- prometheus.MustNewConstMetric(
+		statCheckpointerRestartpointsDoneDesc,
+		prometheus.CounterValue,
+		rpdMetric,
+	)
+
+	wtMetric := 0.0
+	if wt.Valid {
+		wtMetric = float64(wt.Float64)
+	}
+	ch <- prometheus.MustNewConstMetric(
+		statCheckpointerWriteTimeDesc,
+		prometheus.CounterValue,
+		wtMetric,
+	)
+
+	stMetric := 0.0
+	if st.Valid {
+		stMetric = float64(st.Float64)
+	}
+	ch <- prometheus.MustNewConstMetric(
+		statCheckpointerSyncTimeDesc,
+		prometheus.CounterValue,
+		stMetric,
+	)
+
+	bwMetric := 0.0
+	if bw.Valid {
+		bwMetric = float64(bw.Int64)
+	}
+	ch <- prometheus.MustNewConstMetric(
+		statCheckpointerBuffersWrittenDesc,
+		prometheus.CounterValue,
+		bwMetric,
+	)
+
+	srMetric := 0.0
+	if sr.Valid {
+		srMetric = float64(sr.Time.Unix())
+	}
+	ch <- prometheus.MustNewConstMetric(
+		statCheckpointerStatsResetDesc,
+		prometheus.CounterValue,
+		srMetric,
+	)
+
+	return nil
+}
--- a/collector/pg_stat_checkpointer_test.go
+++ b/collector/pg_stat_checkpointer_test.go
@ -0,0 +1,143 @@
+// Copyright 2024 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package collector
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/smartystreets/goconvey/convey"
+)
+
+func TestPGStatCheckpointerCollector(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}
+
+	columns := []string{
+		"num_timed",
+		"num_requested",
+		"restartpoints_timed",
+		"restartpoints_req",
+		"restartpoints_done",
+		"write_time",
+		"sync_time",
+		"buffers_written",
+		"stats_reset"}
+
+	srT, err := time.Parse("2006-01-02 15:04:05.00000-07", "2023-05-25 17:10:42.81132-07")
+	if err != nil {
+		t.Fatalf("Error parsing time: %s", err)
+	}
+
+	rows := sqlmock.NewRows(columns).
+		AddRow(354, 4945, 289097744, 1242257, int64(3275602074), 89320867, 450139, 2034563757, srT)
+	mock.ExpectQuery(sanitizeQuery(statCheckpointerQuery)).WillReturnRows(rows)
+
+	ch := make(chan prometheus.Metric)
+	go func() {
+		defer close(ch)
+		c := PGStatCheckpointerCollector{}
+
+		if err := c.Update(context.Background(), inst, ch); err != nil {
+			t.Errorf("Error calling PGStatCheckpointerCollector.Update: %s", err)
+		}
+	}()
+
+	expected := []MetricResult{
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 354},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 4945},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 289097744},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 1242257},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 3275602074},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 89320867},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 450139},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 2034563757},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 1685059842},
+	}
+
+	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)
+	}
+}
+
+func TestPGStatCheckpointerCollectorNullValues(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}
+
+	columns := []string{
+		"num_timed",
+		"num_requested",
+		"restartpoints_timed",
+		"restartpoints_req",
+		"restartpoints_done",
+		"write_time",
+		"sync_time",
+		"buffers_written",
+		"stats_reset"}
+
+	rows := sqlmock.NewRows(columns).
+		AddRow(nil, nil, nil, nil, nil, nil, nil, nil, nil)
+	mock.ExpectQuery(sanitizeQuery(statCheckpointerQuery)).WillReturnRows(rows)
+
+	ch := make(chan prometheus.Metric)
+	go func() {
+		defer close(ch)
+		c := PGStatCheckpointerCollector{}
+
+		if err := c.Update(context.Background(), inst, ch); err != nil {
+			t.Errorf("Error calling PGStatCheckpointerCollector.Update: %s", err)
+		}
+	}()
+
+	expected := []MetricResult{
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+	}
+
+	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)
+	}
+}