Optimize database write performance

- Use SQLite UPSERT for UpdateLiveRoute to eliminate SELECT+UPDATE/INSERT pattern
- Add connection string optimizations (synchronous=NORMAL, cache_size)
- Add WAL checkpoint configuration for better write performance
- Add index on live_routes(id) for UPDATE operations
- Set WAL autocheckpoint to 1000 pages

These changes should reduce write amplification and improve overall
throughput by:
1. Reducing from 2 queries to 1 for route updates
2. Better WAL checkpoint management
3. More efficient UPDATE operations with dedicated index

internal/database/database.go

@@ -95,7 +95,8 @@ func NewWithConfig(config Config, logger *slog.Logger) (*Database, error) {
 	}
 
 	// Add connection parameters for modernc.org/sqlite
-	dsn := fmt.Sprintf("file:%s?_busy_timeout=5000&_journal_mode=WAL", config.Path)
+	// Enable WAL mode and other performance optimizations
+	dsn := fmt.Sprintf("file:%s?_busy_timeout=5000&_journal_mode=WAL&_synchronous=NORMAL&_cache_size=-512000", config.Path)
 	db, err := sql.Open("sqlite", dsn)
 	if err != nil {
 		return nil, fmt.Errorf("failed to open database: %w", err)
@@ -123,12 +124,14 @@ func NewWithConfig(config Config, logger *slog.Logger) (*Database, error) {
 func (d *Database) Initialize() error {
 	// Set SQLite pragmas for better performance
 	pragmas := []string{
-		"PRAGMA journal_mode=WAL",    // Already set in connection string
-		"PRAGMA synchronous=NORMAL",  // Faster than FULL, still safe
-		"PRAGMA cache_size=-524288",  // 512MB cache
-		"PRAGMA temp_store=MEMORY",   // Use memory for temp tables
-		"PRAGMA mmap_size=268435456", // 256MB memory-mapped I/O
-		"PRAGMA optimize",            // Run optimizer
+		"PRAGMA journal_mode=WAL",        // Already set in connection string
+		"PRAGMA synchronous=NORMAL",      // Faster than FULL, still safe
+		"PRAGMA cache_size=-524288",      // 512MB cache
+		"PRAGMA temp_store=MEMORY",       // Use memory for temp tables
+		"PRAGMA mmap_size=268435456",     // 256MB memory-mapped I/O
+		"PRAGMA wal_autocheckpoint=1000", // Checkpoint every 1000 pages
+		"PRAGMA wal_checkpoint(PASSIVE)", // Checkpoint now
+		"PRAGMA optimize",                // Run optimizer
 	}
 
 	for _, pragma := range pragmas {
@@ -344,33 +347,18 @@ func (d *Database) UpdateLiveRoute(
 	nextHop string,
 	timestamp time.Time,
 ) error {
-	// Check if route already exists
-	var routeID sql.NullString
-	err := d.queryRow(`
-		SELECT id FROM live_routes 
-		WHERE prefix_id = ? AND origin_asn_id = ? AND peer_asn = ? AND withdrawn_at IS NULL`,
-		prefixID.String(), originASNID.String(), peerASN).Scan(&routeID)
-
-	if err != nil && err != sql.ErrNoRows {
-		return err
-	}
-
-	if routeID.Valid {
-		// Route exists and is active, update it
-		err = d.exec(`
-			UPDATE live_routes 
-			SET next_hop = ?, announced_at = ?
-			WHERE id = ?`,
-			nextHop, timestamp, routeID.String)
-	} else {
-		// Either new route or re-announcement of withdrawn route
-		err = d.exec(`
-			INSERT OR REPLACE INTO live_routes 
-			(id, prefix_id, origin_asn_id, peer_asn, next_hop, announced_at, withdrawn_at)
-			VALUES (?, ?, ?, ?, ?, ?, NULL)`,
-			generateUUID().String(), prefixID.String(), originASNID.String(),
-			peerASN, nextHop, timestamp)
-	}
+	// Use SQLite's UPSERT capability to avoid the SELECT+UPDATE/INSERT pattern
+	// This reduces the number of queries and improves performance
+	err := d.exec(`
+		INSERT INTO live_routes (id, prefix_id, origin_asn_id, peer_asn, next_hop, announced_at, withdrawn_at)
+		VALUES (?, ?, ?, ?, ?, ?, NULL)
+		ON CONFLICT(prefix_id, origin_asn_id, peer_asn) DO UPDATE SET
+			next_hop = excluded.next_hop,
+			announced_at = excluded.announced_at,
+			withdrawn_at = NULL
+		WHERE withdrawn_at IS NULL`,
+		generateUUID().String(), prefixID.String(), originASNID.String(),
+		peerASN, nextHop, timestamp)
 
 	return err
 }

internal/database/schema.sql

@@ -99,6 +99,10 @@ CREATE INDEX IF NOT EXISTS idx_live_routes_covering
 	ON live_routes(prefix_id, origin_asn_id, peer_asn, id)
 	WHERE withdrawn_at IS NULL;
 
+-- Index for UPDATE by id operations
+CREATE INDEX IF NOT EXISTS idx_live_routes_id
+	ON live_routes(id);
+
 -- Index for stats queries
 CREATE INDEX IF NOT EXISTS idx_live_routes_stats
 	ON live_routes(withdrawn_at)