[*] prettify code

src/sinks/postgres.go

@@ -20,6 +20,7 @@ import (
 var (
 	cacheLimit      = 512
 	highLoadTimeout = time.Second * 5
+	deleterDelay    = time.Hour
 )
 
 func NewPostgresWriter(ctx context.Context, connstr string, opts *config.MeasurementOpts, metricDefs *metrics.Metrics) (pgw *PostgresWriter, err error) {
@@ -60,8 +61,8 @@ func NewWriterFromPostgresConn(ctx context.Context, conn db.PgxPoolIface, opts *
 	if err = pgw.EnsureBuiltinMetricDummies(); err != nil {
 		return
 	}
-	go pgw.OldPostgresMetricsDeleter()
-	go pgw.UniqueDbnamesListingMaintainer()
+	go pgw.deleteOldPartitions(deleterDelay)
+	go pgw.maintainUniqueSources()
 	go pgw.poll()
 	return
 }
@@ -484,7 +485,8 @@ func (pgw *PostgresWriter) EnsureMetricDbnameTime(metricDbnamePartBounds map[str
 	return nil
 }
 
-func (pgw *PostgresWriter) OldPostgresMetricsDeleter() {
+// deleteOldPartitions is a background task that deletes old partitions from the measurements DB
+func (pgw *PostgresWriter) deleteOldPartitions(delay time.Duration) {
 	metricAgeDaysThreshold := pgw.opts.Retention
 	if metricAgeDaysThreshold <= 0 {
 		return
@@ -493,7 +495,7 @@ func (pgw *PostgresWriter) OldPostgresMetricsDeleter() {
 	select {
 	case <-pgw.сtx.Done():
 		return
-	case <-time.After(time.Hour):
+	case <-time.After(delay):
 		// to reduce distracting log messages at startup
 	}
 
@@ -515,7 +517,7 @@ func (pgw *PostgresWriter) OldPostgresMetricsDeleter() {
 			if len(partsToDrop) > 0 {
 				logger.Infof("Dropping %d old metric partitions one by one...", len(partsToDrop))
 				for _, toDrop := range partsToDrop {
-					sqlDropTable := `DROP TABLE IF EXISTS ` + pgx.Identifier{toDrop}.Sanitize()
+					sqlDropTable := `DROP TABLE IF EXISTS ` + toDrop
 					logger.Debugf("Dropping old metric data partition: %s", toDrop)
 
 					if _, err := pgw.sinkDb.Exec(pgw.сtx, sqlDropTable); err != nil {
@@ -537,7 +539,9 @@ func (pgw *PostgresWriter) OldPostgresMetricsDeleter() {
 	}
 }
 
-func (pgw *PostgresWriter) UniqueDbnamesListingMaintainer() {
+// maintainUniqueSources is a background task that maintains a listing of unique sources for each metric.
+// This is used to avoid listing the same source multiple times in Grafana dropdowns.
+func (pgw *PostgresWriter) maintainUniqueSources() {
 	logger := log.GetLogger(pgw.сtx)
 	// due to metrics deletion the listing can go out of sync (a trigger not really wanted)
 	sqlGetAdvisoryLock := `SELECT pg_try_advisory_lock(1571543679778230000) AS have_lock` // 1571543679778230000 is just a random bigint
@@ -548,8 +552,8 @@ func (pgw *PostgresWriter) UniqueDbnamesListingMaintainer() {
 		UNION
 		SELECT (SELECT MIN(dbname) FROM %s WHERE dbname > t.dbname) FROM t )
 	SELECT dbname FROM t WHERE dbname NOTNULL ORDER BY 1`
-	sqlDelete := `DELETE FROM admin.all_distinct_dbname_metrics WHERE NOT dbname = ANY($1) and metric = $2 RETURNING *`
-	sqlDeleteAll := `DELETE FROM admin.all_distinct_dbname_metrics WHERE metric = $1 RETURNING *`
+	sqlDelete := `DELETE FROM admin.all_distinct_dbname_metrics WHERE NOT dbname = ANY($1) and metric = $2`
+	sqlDeleteAll := `DELETE FROM admin.all_distinct_dbname_metrics WHERE metric = $1`
 	sqlAdd := `
 		INSERT INTO admin.all_distinct_dbname_metrics SELECT u, $2 FROM (select unnest($1::text[]) as u) x
 		WHERE NOT EXISTS (select * from admin.all_distinct_dbname_metrics where dbname = u and metric = $2)