WIP: pg_stat_database by PG version support

collector/models/pgStatDatabase.go

@@ -6,7 +6,7 @@ import (
 
 // +metric=slice
 type PgStatDatabase struct {
-	tableName    struct{}     `pg:"pg_stat_database,discard_unknown_columns"`
+	tableName    struct{}     `pg:"pg_stat_database"`
 	DatID        int64        `pg:"datid" help:"OID of a database" metric:"database_id,type:label"`
 	DatName      string       `pg:"datname" help:"Name of this database" metric:"database,type:label"`
 	NumBackends  int          `pg:"numbackends" help:"Number of backends currently connected to this database" metric:"backends,type:gauge"`
@@ -23,16 +23,16 @@ type PgStatDatabase struct {
 	TempFiles    int64        `pg:"temp_files" help:"Number of temporary files created by queries in this database"  metric:"temp_files_total"`
 	TempBytes    int64        `pg:"temp_bytes" help:"Total amount of data written to temporary files by queries in this database"  metric:"temp_bytes_total"`
 	Deadlocks    int64        `pg:"deadlocks" help:"Number of deadlocks detected in this database"  metric:"deadlocks_total"`
-	checksumFailures int64    `pg:"checksum_failures" help:"Number of data page checksum failures detected in this database" metric:"checksum_failures_count"` // new in PG12
-	checksumLastFailure time.Time `pg:"checksum_last_failure" help:"Time at which the last data page checksum failure was detected in this database" metric:"checksum_last_failure"` // new in PG12
+	ChecksumFailures int64    `pg:"checksum_failures" help:"Number of data page checksum failures detected in this database" metric:"checksum_failures_count"` // new in PG12
+	ChecksumLastFailure time.Time `pg:"checksum_last_failure" help:"Time at which the last data page checksum failure was detected in this database" metric:"checksum_last_failure"` // new in PG12
 	BlkReadTime  Milliseconds `pg:"blk_read_time" help:"Time spent reading data file blocks by backends in this database" metric:"blk_read_seconds_total"`
 	BlkWriteTime Milliseconds `pg:"blk_write_time" help:"Time spent writing data file blocks by backends in this database" metric:"blk_write_seconds_total"`
-	sessionTime  Milliseconds `pg:"session_time" help:"Time spent by database sessions in this database, in milliseconds" metric:"session_time_total"` // new in PG14
-	activeTime   Milliseconds `pg:"active_time" help:"Time spent executing SQL statements in this database, in milliseconds" metric:"active_time_total"` // new in PG14
-	idleInTransactionTime Milliseconds `pg:"idle_in_transaction_time" help:"Time spent idling while in a transaction in this database, in milliseconds" metric:"idle_in_transaction_time_total"` // new in PG14
-	sessions     int64        `pg:"sessions" help:"Total number of sessions established to this database" metric:"sessions_count"` // new in PG14
-	sessionsAbandoned int64   `pg:"sessions_abandoned" help:"Number of database sessions to this database that were terminated because connection to the client was lost" metric:"sessions_abandoned_count"` // new in PG14
-	sessionsFatal int64       `pg:"sessions_fatal" help:"Number of database sessions to this database that were terminated by fatal errors" metric:"sessions_fatal_count"` // new in PG14
-	sessionsKilled int64      `pg:"sessions_killed" help:"Number of database sessions to this database that were terminated by operator intervention" metric:"sessions_killed_count"` // new in PG14
+	SessionTime  Milliseconds `pg:"session_time" help:"Time spent by database sessions in this database, in milliseconds" metric:"session_time_total"` // new in PG14
+	ActiveTime   Milliseconds `pg:"active_time" help:"Time spent executing SQL statements in this database, in milliseconds" metric:"active_time_total"` // new in PG14
+	IdleInTransactionTime Milliseconds `pg:"idle_in_transaction_time" help:"Time spent idling while in a transaction in this database, in milliseconds" metric:"idle_in_transaction_time_total"` // new in PG14
+	Sessions     int64        `pg:"sessions" help:"Total number of sessions established to this database" metric:"sessions_count"` // new in PG14
+	SessionsAbandoned int64   `pg:"sessions_abandoned" help:"Number of database sessions to this database that were terminated because connection to the client was lost" metric:"sessions_abandoned_count"` // new in PG14
+	SessionsFatal int64       `pg:"sessions_fatal" help:"Number of database sessions to this database that were terminated by fatal errors" metric:"sessions_fatal_count"` // new in PG14
+	SessionsKilled int64      `pg:"sessions_killed" help:"Number of database sessions to this database that were terminated by operator intervention" metric:"sessions_killed_count"` // new in PG14
 	StatsReset   time.Time    `pg:"stats_reset" help:"Time at which these statistics were last reset"`
 }

collector/models/pgStatDatabase_gen.go

@@ -140,7 +140,7 @@ func (r *PgStatDatabase) ToMetrics(namespace string, subsystem string, ch chan<-
 	)
 
 	// checksum_failures_count (CounterValue)
-	checksumFailuresCount := float64(r.checksumFailures)
+	checksumFailuresCount := float64(r.ChecksumFailures)
 	ch <- prometheus.MustNewConstMetric(
 		prometheus.NewDesc(
 			prometheus.BuildFQName(namespace, subsystem, `checksum_failures_count`), `Number of data page checksum failures detected in this database`, nil, labels,
@@ -149,10 +149,10 @@ func (r *PgStatDatabase) ToMetrics(namespace string, subsystem string, ch chan<-
 
 	// checksum_last_failure (CounterValue)
 	var checksumLastFailure float64
-	if r.checksumLastFailure.IsZero() {
+	if r.ChecksumLastFailure.IsZero() {
 		checksumLastFailure = float64(0)
 	} else {
-		checksumLastFailure = float64(r.checksumLastFailure.Unix())
+		checksumLastFailure = float64(r.ChecksumLastFailure.Unix())
 	}
 	ch <- prometheus.MustNewConstMetric(
 		prometheus.NewDesc(
@@ -177,55 +177,55 @@ func (r *PgStatDatabase) ToMetrics(namespace string, subsystem string, ch chan<-
 	)
 
 	// session_time_total (CounterValue)
-	sessionTimeTotal := r.sessionTime.Seconds()
+	sessionTimeTotal := r.SessionTime.Seconds()
 	ch <- prometheus.MustNewConstMetric(
 		prometheus.NewDesc(
 			prometheus.BuildFQName(namespace, subsystem, `session_time_total`), `Time spent by database sessions in this database, in milliseconds`, nil, labels,
 		), prometheus.CounterValue, sessionTimeTotal,
 	)
 
 	// active_time_total (CounterValue)
-	activeTimeTotal := r.activeTime.Seconds()
+	activeTimeTotal := r.ActiveTime.Seconds()
 	ch <- prometheus.MustNewConstMetric(
 		prometheus.NewDesc(
 			prometheus.BuildFQName(namespace, subsystem, `active_time_total`), `Time spent executing SQL statements in this database, in milliseconds`, nil, labels,
 		), prometheus.CounterValue, activeTimeTotal,
 	)
 
 	// idle_in_transaction_time_total (CounterValue)
-	idleInTransactionTimeTotal := r.idleInTransactionTime.Seconds()
+	idleInTransactionTimeTotal := r.IdleInTransactionTime.Seconds()
 	ch <- prometheus.MustNewConstMetric(
 		prometheus.NewDesc(
 			prometheus.BuildFQName(namespace, subsystem, `idle_in_transaction_time_total`), `Time spent idling while in a transaction in this database, in milliseconds`, nil, labels,
 		), prometheus.CounterValue, idleInTransactionTimeTotal,
 	)
 
 	// sessions_count (CounterValue)
-	sessionsCount := float64(r.sessions)
+	sessionsCount := float64(r.Sessions)
 	ch <- prometheus.MustNewConstMetric(
 		prometheus.NewDesc(
 			prometheus.BuildFQName(namespace, subsystem, `sessions_count`), `Total number of sessions established to this database`, nil, labels,
 		), prometheus.CounterValue, sessionsCount,
 	)
 
 	// sessions_abandoned_count (CounterValue)
-	sessionsAbandonedCount := float64(r.sessionsAbandoned)
+	sessionsAbandonedCount := float64(r.SessionsAbandoned)
 	ch <- prometheus.MustNewConstMetric(
 		prometheus.NewDesc(
 			prometheus.BuildFQName(namespace, subsystem, `sessions_abandoned_count`), `Number of database sessions to this database that were terminated because connection to the client was lost`, nil, labels,
 		), prometheus.CounterValue, sessionsAbandonedCount,
 	)
 
 	// sessions_fatal_count (CounterValue)
-	sessionsFatalCount := float64(r.sessionsFatal)
+	sessionsFatalCount := float64(r.SessionsFatal)
 	ch <- prometheus.MustNewConstMetric(
 		prometheus.NewDesc(
 			prometheus.BuildFQName(namespace, subsystem, `sessions_fatal_count`), `Number of database sessions to this database that were terminated by fatal errors`, nil, labels,
 		), prometheus.CounterValue, sessionsFatalCount,
 	)
 
 	// sessions_killed_count (CounterValue)
-	sessionsKilledCount := float64(r.sessionsKilled)
+	sessionsKilledCount := float64(r.SessionsKilled)
 	ch <- prometheus.MustNewConstMetric(
 		prometheus.NewDesc(
 			prometheus.BuildFQName(namespace, subsystem, `sessions_killed_count`), `Number of database sessions to this database that were terminated by operator intervention`, nil, labels,

collector/stat_database.go

@@ -2,6 +2,7 @@ package collector
 
 import (
 	"context"
+	"fmt"
 
 	"github.com/go-pg/pg/v9"
 	"github.com/prometheus/client_golang/prometheus"
@@ -39,12 +40,25 @@ func (ScrapeDatabase) Type() ScrapeType {
 
 // Scrape collects data from database connection and sends it over channel as prometheus metric.
 func (ScrapeDatabase) Scrape(ctx context.Context, db *pg.DB, ch chan<- prometheus.Metric) error {
+	// we create a query based on the given commandline flags
+	columns := "numbackends, xact_commit, xact_rollback, blks_read, blks_hit, tup_returned, tup_fetched, tup_inserted, tup_updated, tup_deleted, conflicts, temp_files, temp_bytes, deadlocks, blk_read_time, blk_write_time"
+
+	if pgversion >= 120000 {
+		columns += ", checksum_failures, checksum_last_failure"
+	}
+
+	if pgversion >= 140000 {
+		columns += ", session_time, active_time, idle_in_transaction_time, sessions, sessions_abandoned, sessions_fatal, sessions_killed"
+	}
+
+	qs := fmt.Sprintf(`SELECT datid, datname, %s, stats_reset FROM pg_stat_database`+
+		` WHERE datname IN (?)`,
+		columns)
+
 	var statDatabase models.PgStatDatabaseSlice
-	if err := db.ModelContext(ctx, &statDatabase).Where("datname IN (?)", pg.In(collectDatabases)).
-		Select(); err != nil {
+	if _, err := db.QueryContext(ctx, &statDatabase, qs, pg.In(collectDatabases)); err != nil {
 		return err
 	}
-
 	if err := statDatabase.ToMetrics(namespace, statdatabase, ch); err != nil {
 		return err
 	}