Switch to incremental vacuum for non-blocking space reclamation

- Use PRAGMA incremental_vacuum instead of full VACUUM
- Frees ~1000 pages (~4MB) per run without blocking writes
- Run every 10 minutes instead of 6 hours since it's lightweight
- Set auto_vacuum=INCREMENTAL pragma for new databases
- Remove blocking VACUUM on startup

internal/database/database.go

@@ -113,6 +113,7 @@ func (d *Database) Initialize() error {
 		"PRAGMA wal_checkpoint(TRUNCATE)", // Checkpoint and truncate WAL now
 		"PRAGMA busy_timeout=5000",        // 5 second busy timeout
 		"PRAGMA analysis_limit=0",         // Disable automatic ANALYZE
+		"PRAGMA auto_vacuum=INCREMENTAL",  // Enable incremental vacuum (new DBs only)
 	}
 
 	for _, pragma := range pragmas {
@@ -126,12 +127,6 @@ func (d *Database) Initialize() error {
 		return err
 	}
 
-	// Run VACUUM on startup to optimize database
-	d.logger.Info("Running VACUUM to optimize database (this may take a moment)")
-	if err := d.exec("VACUUM"); err != nil {
-		d.logger.Warn("Failed to VACUUM database", "error", err)
-	}
-
 	return nil
 }
 
@@ -1951,11 +1946,15 @@ func (d *Database) getIPv6Info(ctx context.Context, ip string, parsedIP net.IP)
 	return info, nil
 }
 
-// Vacuum runs the SQLite VACUUM command to reclaim unused space and defragment the database.
+// Vacuum runs incremental vacuum to reclaim unused pages without blocking writes.
+// It frees up to the specified number of pages per call (0 = all freeable pages).
 func (d *Database) Vacuum(ctx context.Context) error {
-	_, err := d.db.ExecContext(ctx, "VACUUM")
+	// Free up to 1000 pages per call (~4MB with default 4KB page size)
+	// This keeps each vacuum operation quick and non-blocking
+	const pagesToFree = 1000
+	_, err := d.db.ExecContext(ctx, fmt.Sprintf("PRAGMA incremental_vacuum(%d)", pagesToFree))
 	if err != nil {
-		return fmt.Errorf("failed to vacuum database: %w", err)
+		return fmt.Errorf("failed to run incremental vacuum: %w", err)
 	}
 
 	return nil

internal/routewatch/dbmaintainer.go

@@ -12,14 +12,19 @@ import (
 
 // Database maintenance configuration constants.
 const (
-	// vacuumInterval is how often to run VACUUM.
-	vacuumInterval = 6 * time.Hour
+	// vacuumInterval is how often to run incremental vacuum.
+	// Since incremental vacuum only frees ~1000 pages (~4MB) per run,
+	// we run it frequently to keep up with deletions.
+	vacuumInterval = 10 * time.Minute
 
 	// analyzeInterval is how often to run ANALYZE.
 	analyzeInterval = 1 * time.Hour
 
-	// maintenanceTimeout is the max time for a maintenance operation.
-	maintenanceTimeout = 5 * time.Minute
+	// vacuumTimeout is the max time for incremental vacuum (should be quick).
+	vacuumTimeout = 30 * time.Second
+
+	// analyzeTimeout is the max time for ANALYZE.
+	analyzeTimeout = 5 * time.Minute
 )
 
 // DBMaintainer handles background database maintenance tasks.
@@ -91,12 +96,12 @@ func (m *DBMaintainer) run() {
 	}
 }
 
-// runVacuum performs a VACUUM operation on the database.
+// runVacuum performs an incremental vacuum operation on the database.
 func (m *DBMaintainer) runVacuum() {
-	ctx, cancel := context.WithTimeout(context.Background(), maintenanceTimeout)
+	ctx, cancel := context.WithTimeout(context.Background(), vacuumTimeout)
 	defer cancel()
 
-	m.logger.Info("Starting database VACUUM")
+	m.logger.Debug("Running incremental vacuum")
 	startTime := time.Now()
 
 	err := m.db.Vacuum(ctx)
@@ -110,15 +115,15 @@ func (m *DBMaintainer) runVacuum() {
 	m.statsMu.Unlock()
 
 	if err != nil {
-		m.logger.Error("VACUUM failed", "error", err, "duration", time.Since(startTime))
+		m.logger.Error("Incremental vacuum failed", "error", err, "duration", time.Since(startTime))
 	} else {
-		m.logger.Info("VACUUM completed", "duration", time.Since(startTime))
+		m.logger.Debug("Incremental vacuum completed", "duration", time.Since(startTime))
 	}
 }
 
 // runAnalyze performs an ANALYZE operation on the database.
 func (m *DBMaintainer) runAnalyze() {
-	ctx, cancel := context.WithTimeout(context.Background(), maintenanceTimeout)
+	ctx, cancel := context.WithTimeout(context.Background(), analyzeTimeout)
 	defer cancel()
 
 	m.logger.Info("Starting database ANALYZE")