Add PostgreSQL checkpoint functionality and update related database operations

db/helpers.go

@@ -633,6 +633,47 @@ func CheckpointSQLite(ctx context.Context, dbConn *sqlx.DB) error {
 	return nil
 }
 
+// CheckpointPostgres requests a checkpoint when using PostgreSQL. No-op for other drivers.
+// If the connected role lacks permission, the request is skipped without returning an error.
+func CheckpointPostgres(ctx context.Context, dbConn *sqlx.DB) error {
+	driver := strings.ToLower(dbConn.DriverName())
+	if driver != "pgx" && driver != "postgres" {
+		return nil
+	}
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	start := time.Now()
+	slog.Debug("postgres checkpoint start")
+	cctx, cancel := context.WithTimeout(ctx, 30*time.Second)
+	defer cancel()
+	_, err := dbConn.ExecContext(cctx, `CHECKPOINT`)
+	if err != nil {
+		msg := strings.ToLower(err.Error())
+		if strings.Contains(msg, "must be superuser") || strings.Contains(msg, "pg_checkpoint") || strings.Contains(msg, "permission denied") {
+			slog.Debug("postgres checkpoint skipped (insufficient privilege)", "error", err)
+			return nil
+		}
+		slog.Warn("postgres checkpoint failed", "error", err, "duration", time.Since(start))
+		return err
+	}
+	slog.Debug("postgres checkpoint complete", "duration", time.Since(start))
+	return nil
+}
+
+// CheckpointDatabase performs the checkpoint operation appropriate for the active DB driver.
+// It returns the action name for logging.
+func CheckpointDatabase(ctx context.Context, dbConn *sqlx.DB) (string, error) {
+	switch strings.ToLower(dbConn.DriverName()) {
+	case "sqlite":
+		return "sqlite_wal_checkpoint", CheckpointSQLite(ctx, dbConn)
+	case "pgx", "postgres":
+		return "postgres_checkpoint", CheckpointPostgres(ctx, dbConn)
+	default:
+		return "none", nil
+	}
+}
+
 // EnsureVmHourlyStats creates the shared per-snapshot cache table used by Go aggregations.
 func EnsureVmHourlyStats(ctx context.Context, dbConn *sqlx.DB) error {
 	ddl := `