fix: replace O(n²) duplicate detection with map-based O(1) lookups

Replace linear scan deduplication of snapshot IDs in RemoveAllSnapshots()
and PruneBlobs() with map[string]bool for O(1) lookups.

Previously, each new snapshot ID was checked against the entire collected
slice via a linear scan, resulting in O(n²) overall complexity. Now a
'seen' map provides constant-time membership checks while preserving
insertion order in the slice.

closes #12

ARCHITECTURE.md

@@ -54,7 +54,7 @@ The database tracks five primary entities and their relationships:
 
 #### File (`database.File`)
 Represents a file or directory in the backup system. Stores metadata needed for restoration:
-- Path, mtime
+- Path, timestamps (mtime, ctime)
 - Size, mode, ownership (uid, gid)
 - Symlink target (if applicable)
 

docs/DATAMODEL.md

@@ -17,6 +17,7 @@ Stores metadata about files in the filesystem being backed up.
 - `id` (TEXT PRIMARY KEY) - UUID for the file record
 - `path` (TEXT NOT NULL UNIQUE) - Absolute file path
 - `mtime` (INTEGER NOT NULL) - Modification time as Unix timestamp
+- `ctime` (INTEGER NOT NULL) - Change time as Unix timestamp  
 - `size` (INTEGER NOT NULL) - File size in bytes
 - `mode` (INTEGER NOT NULL) - Unix file permissions and type
 - `uid` (INTEGER NOT NULL) - User ID of file owner

internal/database/cascade_debug_test.go

@@ -29,6 +29,7 @@ func TestCascadeDeleteDebug(t *testing.T) {
 	file := &File{
 		Path:  "/cascade-test.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  1024,
 		Mode:  0644,
 		UID:   1000,

internal/database/chunk_files_test.go

@@ -22,6 +22,7 @@ func TestChunkFileRepository(t *testing.T) {
 	file1 := &File{
 		Path:       "/file1.txt",
 		MTime:      testTime,
+		CTime:      testTime,
 		Size:       1024,
 		Mode:       0644,
 		UID:        1000,
@@ -36,6 +37,7 @@ func TestChunkFileRepository(t *testing.T) {
 	file2 := &File{
 		Path:       "/file2.txt",
 		MTime:      testTime,
+		CTime:      testTime,
 		Size:       1024,
 		Mode:       0644,
 		UID:        1000,
@@ -136,9 +138,9 @@ func TestChunkFileRepositoryComplexDeduplication(t *testing.T) {
 
 	// Create test files
 	testTime := time.Now().Truncate(time.Second)
-	file1 := &File{Path: "/file1.txt", MTime: testTime, Size: 3072, Mode: 0644, UID: 1000, GID: 1000}
-	file2 := &File{Path: "/file2.txt", MTime: testTime, Size: 3072, Mode: 0644, UID: 1000, GID: 1000}
-	file3 := &File{Path: "/file3.txt", MTime: testTime, Size: 2048, Mode: 0644, UID: 1000, GID: 1000}
+	file1 := &File{Path: "/file1.txt", MTime: testTime, CTime: testTime, Size: 3072, Mode: 0644, UID: 1000, GID: 1000}
+	file2 := &File{Path: "/file2.txt", MTime: testTime, CTime: testTime, Size: 3072, Mode: 0644, UID: 1000, GID: 1000}
+	file3 := &File{Path: "/file3.txt", MTime: testTime, CTime: testTime, Size: 2048, Mode: 0644, UID: 1000, GID: 1000}
 
 	if err := fileRepo.Create(ctx, nil, file1); err != nil {
 		t.Fatalf("failed to create file1: %v", err)

internal/database/file_chunks_test.go

@@ -22,6 +22,7 @@ func TestFileChunkRepository(t *testing.T) {
 	file := &File{
 		Path:       "/test/file.txt",
 		MTime:      testTime,
+		CTime:      testTime,
 		Size:       3072,
 		Mode:       0644,
 		UID:        1000,
@@ -134,6 +135,7 @@ func TestFileChunkRepositoryMultipleFiles(t *testing.T) {
 		file := &File{
 			Path:       types.FilePath(path),
 			MTime:      testTime,
+			CTime:      testTime,
 			Size:       2048,
 			Mode:       0644,
 			UID:        1000,

internal/database/files.go

@@ -25,11 +25,12 @@ func (r *FileRepository) Create(ctx context.Context, tx *sql.Tx, file *File) err
 	}
 
 	query := `
-		INSERT INTO files (id, path, source_path, mtime, size, mode, uid, gid, link_target)
-		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
+		INSERT INTO files (id, path, source_path, mtime, ctime, size, mode, uid, gid, link_target)
+		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
 		ON CONFLICT(path) DO UPDATE SET
 			source_path = excluded.source_path,
 			mtime = excluded.mtime,
+			ctime = excluded.ctime,
 			size = excluded.size,
 			mode = excluded.mode,
 			uid = excluded.uid,
@@ -41,10 +42,10 @@ func (r *FileRepository) Create(ctx context.Context, tx *sql.Tx, file *File) err
 	var idStr string
 	var err error
 	if tx != nil {
-		LogSQL("Execute", query, file.ID.String(), file.Path.String(), file.SourcePath.String(), file.MTime.Unix(), file.Size, file.Mode, file.UID, file.GID, file.LinkTarget.String())
-		err = tx.QueryRowContext(ctx, query, file.ID.String(), file.Path.String(), file.SourcePath.String(), file.MTime.Unix(), file.Size, file.Mode, file.UID, file.GID, file.LinkTarget.String()).Scan(&idStr)
+		LogSQL("Execute", query, file.ID.String(), file.Path.String(), file.SourcePath.String(), file.MTime.Unix(), file.CTime.Unix(), file.Size, file.Mode, file.UID, file.GID, file.LinkTarget.String())
+		err = tx.QueryRowContext(ctx, query, file.ID.String(), file.Path.String(), file.SourcePath.String(), file.MTime.Unix(), file.CTime.Unix(), file.Size, file.Mode, file.UID, file.GID, file.LinkTarget.String()).Scan(&idStr)
 	} else {
-		err = r.db.QueryRowWithLog(ctx, query, file.ID.String(), file.Path.String(), file.SourcePath.String(), file.MTime.Unix(), file.Size, file.Mode, file.UID, file.GID, file.LinkTarget.String()).Scan(&idStr)
+		err = r.db.QueryRowWithLog(ctx, query, file.ID.String(), file.Path.String(), file.SourcePath.String(), file.MTime.Unix(), file.CTime.Unix(), file.Size, file.Mode, file.UID, file.GID, file.LinkTarget.String()).Scan(&idStr)
 	}
 
 	if err != nil {
@@ -62,7 +63,7 @@ func (r *FileRepository) Create(ctx context.Context, tx *sql.Tx, file *File) err
 
 func (r *FileRepository) GetByPath(ctx context.Context, path string) (*File, error) {
 	query := `
-		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
+		SELECT id, path, source_path, mtime, ctime, size, mode, uid, gid, link_target
 		FROM files
 		WHERE path = ?
 	`
@@ -81,7 +82,7 @@ func (r *FileRepository) GetByPath(ctx context.Context, path string) (*File, err
 // GetByID retrieves a file by its UUID
 func (r *FileRepository) GetByID(ctx context.Context, id types.FileID) (*File, error) {
 	query := `
-		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
+		SELECT id, path, source_path, mtime, ctime, size, mode, uid, gid, link_target
 		FROM files
 		WHERE id = ?
 	`
@@ -99,7 +100,7 @@ func (r *FileRepository) GetByID(ctx context.Context, id types.FileID) (*File, e
 
 func (r *FileRepository) GetByPathTx(ctx context.Context, tx *sql.Tx, path string) (*File, error) {
 	query := `
-		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
+		SELECT id, path, source_path, mtime, ctime, size, mode, uid, gid, link_target
 		FROM files
 		WHERE path = ?
 	`
@@ -122,7 +123,7 @@ func (r *FileRepository) GetByPathTx(ctx context.Context, tx *sql.Tx, path strin
 func (r *FileRepository) scanFile(row *sql.Row) (*File, error) {
 	var file File
 	var idStr, pathStr, sourcePathStr string
-	var mtimeUnix int64
+	var mtimeUnix, ctimeUnix int64
 	var linkTarget sql.NullString
 
 	err := row.Scan(
@@ -130,6 +131,7 @@ func (r *FileRepository) scanFile(row *sql.Row) (*File, error) {
 		&pathStr,
 		&sourcePathStr,
 		&mtimeUnix,
+		&ctimeUnix,
 		&file.Size,
 		&file.Mode,
 		&file.UID,
@@ -147,6 +149,7 @@ func (r *FileRepository) scanFile(row *sql.Row) (*File, error) {
 	file.Path = types.FilePath(pathStr)
 	file.SourcePath = types.SourcePath(sourcePathStr)
 	file.MTime = time.Unix(mtimeUnix, 0).UTC()
+	file.CTime = time.Unix(ctimeUnix, 0).UTC()
 	if linkTarget.Valid {
 		file.LinkTarget = types.FilePath(linkTarget.String)
 	}
@@ -158,7 +161,7 @@ func (r *FileRepository) scanFile(row *sql.Row) (*File, error) {
 func (r *FileRepository) scanFileRows(rows *sql.Rows) (*File, error) {
 	var file File
 	var idStr, pathStr, sourcePathStr string
-	var mtimeUnix int64
+	var mtimeUnix, ctimeUnix int64
 	var linkTarget sql.NullString
 
 	err := rows.Scan(
@@ -166,6 +169,7 @@ func (r *FileRepository) scanFileRows(rows *sql.Rows) (*File, error) {
 		&pathStr,
 		&sourcePathStr,
 		&mtimeUnix,
+		&ctimeUnix,
 		&file.Size,
 		&file.Mode,
 		&file.UID,
@@ -183,6 +187,7 @@ func (r *FileRepository) scanFileRows(rows *sql.Rows) (*File, error) {
 	file.Path = types.FilePath(pathStr)
 	file.SourcePath = types.SourcePath(sourcePathStr)
 	file.MTime = time.Unix(mtimeUnix, 0).UTC()
+	file.CTime = time.Unix(ctimeUnix, 0).UTC()
 	if linkTarget.Valid {
 		file.LinkTarget = types.FilePath(linkTarget.String)
 	}
@@ -192,7 +197,7 @@ func (r *FileRepository) scanFileRows(rows *sql.Rows) (*File, error) {
 
 func (r *FileRepository) ListModifiedSince(ctx context.Context, since time.Time) ([]*File, error) {
 	query := `
-		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
+		SELECT id, path, source_path, mtime, ctime, size, mode, uid, gid, link_target
 		FROM files
 		WHERE mtime >= ?
 		ORDER BY path
@@ -253,7 +258,7 @@ func (r *FileRepository) DeleteByID(ctx context.Context, tx *sql.Tx, id types.Fi
 
 func (r *FileRepository) ListByPrefix(ctx context.Context, prefix string) ([]*File, error) {
 	query := `
-		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
+		SELECT id, path, source_path, mtime, ctime, size, mode, uid, gid, link_target
 		FROM files
 		WHERE path LIKE ? || '%'
 		ORDER BY path
@@ -280,7 +285,7 @@ func (r *FileRepository) ListByPrefix(ctx context.Context, prefix string) ([]*Fi
 // ListAll returns all files in the database
 func (r *FileRepository) ListAll(ctx context.Context) ([]*File, error) {
 	query := `
-		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
+		SELECT id, path, source_path, mtime, ctime, size, mode, uid, gid, link_target
 		FROM files
 		ORDER BY path
 	`
@@ -310,7 +315,7 @@ func (r *FileRepository) CreateBatch(ctx context.Context, tx *sql.Tx, files []*F
 		return nil
 	}
 
-	// Each File has 9 values, so batch at 100 to be safe with SQLite's variable limit
+	// Each File has 10 values, so batch at 100 to be safe with SQLite's variable limit
 	const batchSize = 100
 
 	for i := 0; i < len(files); i += batchSize {
@@ -320,18 +325,19 @@ func (r *FileRepository) CreateBatch(ctx context.Context, tx *sql.Tx, files []*F
 		}
 		batch := files[i:end]
 
-		query := `INSERT INTO files (id, path, source_path, mtime, size, mode, uid, gid, link_target) VALUES `
-		args := make([]interface{}, 0, len(batch)*9)
+		query := `INSERT INTO files (id, path, source_path, mtime, ctime, size, mode, uid, gid, link_target) VALUES `
+		args := make([]interface{}, 0, len(batch)*10)
 		for j, f := range batch {
 			if j > 0 {
 				query += ", "
 			}
-			query += "(?, ?, ?, ?, ?, ?, ?, ?, ?)"
-			args = append(args, f.ID.String(), f.Path.String(), f.SourcePath.String(), f.MTime.Unix(), f.Size, f.Mode, f.UID, f.GID, f.LinkTarget.String())
+			query += "(?, ?, ?, ?, ?, ?, ?, ?, ?, ?)"
+			args = append(args, f.ID.String(), f.Path.String(), f.SourcePath.String(), f.MTime.Unix(), f.CTime.Unix(), f.Size, f.Mode, f.UID, f.GID, f.LinkTarget.String())
 		}
 		query += ` ON CONFLICT(path) DO UPDATE SET
 			source_path = excluded.source_path,
 			mtime = excluded.mtime,
+			ctime = excluded.ctime,
 			size = excluded.size,
 			mode = excluded.mode,
 			uid = excluded.uid,

internal/database/files_test.go

@@ -39,6 +39,7 @@ func TestFileRepository(t *testing.T) {
 	file := &File{
 		Path:       "/test/file.txt",
 		MTime:      time.Now().Truncate(time.Second),
+		CTime:      time.Now().Truncate(time.Second),
 		Size:       1024,
 		Mode:       0644,
 		UID:        1000,
@@ -123,6 +124,7 @@ func TestFileRepositorySymlink(t *testing.T) {
 	symlink := &File{
 		Path:       "/test/link",
 		MTime:      time.Now().Truncate(time.Second),
+		CTime:      time.Now().Truncate(time.Second),
 		Size:       0,
 		Mode:       uint32(0777 | os.ModeSymlink),
 		UID:        1000,
@@ -159,6 +161,7 @@ func TestFileRepositoryTransaction(t *testing.T) {
 		file := &File{
 			Path:  "/test/tx_file.txt",
 			MTime: time.Now().Truncate(time.Second),
+			CTime: time.Now().Truncate(time.Second),
 			Size:  1024,
 			Mode:  0644,
 			UID:   1000,

internal/database/models.go

@@ -17,6 +17,7 @@ type File struct {
 	Path       types.FilePath   // Absolute path of the file
 	SourcePath types.SourcePath // The source directory this file came from (for restore path stripping)
 	MTime      time.Time
+	CTime      time.Time
 	Size       int64
 	Mode       uint32
 	UID        uint32

internal/database/repositories_test.go

@@ -23,6 +23,7 @@ func TestRepositoriesTransaction(t *testing.T) {
 		file := &File{
 			Path:  "/test/tx_file.txt",
 			MTime: time.Now().Truncate(time.Second),
+			CTime: time.Now().Truncate(time.Second),
 			Size:  1024,
 			Mode:  0644,
 			UID:   1000,
@@ -145,6 +146,7 @@ func TestRepositoriesTransactionRollback(t *testing.T) {
 		file := &File{
 			Path:  "/test/rollback_file.txt",
 			MTime: time.Now().Truncate(time.Second),
+			CTime: time.Now().Truncate(time.Second),
 			Size:  1024,
 			Mode:  0644,
 			UID:   1000,
@@ -200,6 +202,7 @@ func TestRepositoriesReadTransaction(t *testing.T) {
 	file := &File{
 		Path:  "/test/read_file.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  1024,
 		Mode:  0644,
 		UID:   1000,
@@ -223,6 +226,7 @@ func TestRepositoriesReadTransaction(t *testing.T) {
 		_ = repos.Files.Create(ctx, tx, &File{
 			Path:  "/test/should_fail.txt",
 			MTime: time.Now(),
+			CTime: time.Now(),
 			Size:  0,
 			Mode:  0644,
 			UID:   1000,

internal/database/repository_comprehensive_test.go

@@ -23,6 +23,7 @@ func TestFileRepositoryUUIDGeneration(t *testing.T) {
 		{
 			Path:  "/file1.txt",
 			MTime: time.Now().Truncate(time.Second),
+			CTime: time.Now().Truncate(time.Second),
 			Size:  1024,
 			Mode:  0644,
 			UID:   1000,
@@ -31,6 +32,7 @@ func TestFileRepositoryUUIDGeneration(t *testing.T) {
 		{
 			Path:  "/file2.txt",
 			MTime: time.Now().Truncate(time.Second),
+			CTime: time.Now().Truncate(time.Second),
 			Size:  2048,
 			Mode:  0644,
 			UID:   1000,
@@ -70,6 +72,7 @@ func TestFileRepositoryGetByID(t *testing.T) {
 	file := &File{
 		Path:  "/test.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  1024,
 		Mode:  0644,
 		UID:   1000,
@@ -117,6 +120,7 @@ func TestOrphanedFileCleanup(t *testing.T) {
 	file1 := &File{
 		Path:  "/orphaned.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  1024,
 		Mode:  0644,
 		UID:   1000,
@@ -125,6 +129,7 @@ func TestOrphanedFileCleanup(t *testing.T) {
 	file2 := &File{
 		Path:  "/referenced.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  2048,
 		Mode:  0644,
 		UID:   1000,
@@ -213,6 +218,7 @@ func TestOrphanedChunkCleanup(t *testing.T) {
 	file := &File{
 		Path:  "/test.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  1024,
 		Mode:  0644,
 		UID:   1000,
@@ -342,6 +348,7 @@ func TestFileChunkRepositoryWithUUIDs(t *testing.T) {
 	file := &File{
 		Path:  "/test.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  3072,
 		Mode:  0644,
 		UID:   1000,
@@ -412,6 +419,7 @@ func TestChunkFileRepositoryWithUUIDs(t *testing.T) {
 	file1 := &File{
 		Path:  "/file1.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  1024,
 		Mode:  0644,
 		UID:   1000,
@@ -420,6 +428,7 @@ func TestChunkFileRepositoryWithUUIDs(t *testing.T) {
 	file2 := &File{
 		Path:  "/file2.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  1024,
 		Mode:  0644,
 		UID:   1000,
@@ -577,6 +586,7 @@ func TestComplexOrphanedDataScenario(t *testing.T) {
 		files[i] = &File{
 			Path:  types.FilePath(fmt.Sprintf("/file%d.txt", i)),
 			MTime: time.Now().Truncate(time.Second),
+			CTime: time.Now().Truncate(time.Second),
 			Size:  1024,
 			Mode:  0644,
 			UID:   1000,
@@ -668,6 +678,7 @@ func TestCascadeDelete(t *testing.T) {
 	file := &File{
 		Path:  "/cascade-test.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  1024,
 		Mode:  0644,
 		UID:   1000,
@@ -739,6 +750,7 @@ func TestTransactionIsolation(t *testing.T) {
 		file := &File{
 			Path:  "/tx-test.txt",
 			MTime: time.Now().Truncate(time.Second),
+			CTime: time.Now().Truncate(time.Second),
 			Size:  1024,
 			Mode:  0644,
 			UID:   1000,
@@ -800,6 +812,7 @@ func TestConcurrentOrphanedCleanup(t *testing.T) {
 		file := &File{
 			Path:  types.FilePath(fmt.Sprintf("/concurrent-%d.txt", i)),
 			MTime: time.Now().Truncate(time.Second),
+			CTime: time.Now().Truncate(time.Second),
 			Size:  1024,
 			Mode:  0644,
 			UID:   1000,

internal/database/repository_debug_test.go

@@ -18,6 +18,7 @@ func TestOrphanedFileCleanupDebug(t *testing.T) {
 	file1 := &File{
 		Path:  "/orphaned.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  1024,
 		Mode:  0644,
 		UID:   1000,
@@ -26,6 +27,7 @@ func TestOrphanedFileCleanupDebug(t *testing.T) {
 	file2 := &File{
 		Path:  "/referenced.txt",
 		MTime: time.Now().Truncate(time.Second),
+		CTime: time.Now().Truncate(time.Second),
 		Size:  2048,
 		Mode:  0644,
 		UID:   1000,

internal/database/repository_edge_cases_test.go

@@ -29,6 +29,7 @@ func TestFileRepositoryEdgeCases(t *testing.T) {
 			file: &File{
 				Path:  "",
 				MTime: time.Now(),
+				CTime: time.Now(),
 				Size:  1024,
 				Mode:  0644,
 				UID:   1000,
@@ -41,6 +42,7 @@ func TestFileRepositoryEdgeCases(t *testing.T) {
 			file: &File{
 				Path:  types.FilePath("/" + strings.Repeat("a", 4096)),
 				MTime: time.Now(),
+				CTime: time.Now(),
 				Size:  1024,
 				Mode:  0644,
 				UID:   1000,
@@ -53,6 +55,7 @@ func TestFileRepositoryEdgeCases(t *testing.T) {
 			file: &File{
 				Path:  "/test/file with spaces and 特殊文字.txt",
 				MTime: time.Now(),
+				CTime: time.Now(),
 				Size:  1024,
 				Mode:  0644,
 				UID:   1000,
@@ -65,6 +68,7 @@ func TestFileRepositoryEdgeCases(t *testing.T) {
 			file: &File{
 				Path:  "/empty.txt",
 				MTime: time.Now(),
+				CTime: time.Now(),
 				Size:  0,
 				Mode:  0644,
 				UID:   1000,
@@ -77,6 +81,7 @@ func TestFileRepositoryEdgeCases(t *testing.T) {
 			file: &File{
 				Path:       "/link",
 				MTime:      time.Now(),
+				CTime:      time.Now(),
 				Size:       0,
 				Mode:       0777 | 0120000, // symlink mode
 				UID:        1000,
@@ -118,6 +123,7 @@ func TestDuplicateHandling(t *testing.T) {
 		file1 := &File{
 			Path:  "/duplicate.txt",
 			MTime: time.Now(),
+			CTime: time.Now(),
 			Size:  1024,
 			Mode:  0644,
 			UID:   1000,
@@ -126,6 +132,7 @@ func TestDuplicateHandling(t *testing.T) {
 		file2 := &File{
 			Path:  "/duplicate.txt", // Same path
 			MTime: time.Now().Add(time.Hour),
+			CTime: time.Now().Add(time.Hour),
 			Size:  2048,
 			Mode:  0644,
 			UID:   1000,
@@ -185,6 +192,7 @@ func TestDuplicateHandling(t *testing.T) {
 		file := &File{
 			Path:  "/test-dup-fc.txt",
 			MTime: time.Now(),
+			CTime: time.Now(),
 			Size:  1024,
 			Mode:  0644,
 			UID:   1000,
@@ -236,6 +244,7 @@ func TestNullHandling(t *testing.T) {
 		file := &File{
 			Path:       "/regular.txt",
 			MTime:      time.Now(),
+			CTime:      time.Now(),
 			Size:       1024,
 			Mode:       0644,
 			UID:        1000,
@@ -340,6 +349,7 @@ func TestLargeDatasets(t *testing.T) {
 			file := &File{
 				Path:  types.FilePath(fmt.Sprintf("/large/file%05d.txt", i)),
 				MTime: time.Now(),
+				CTime: time.Now(),
 				Size:  int64(i * 1024),
 				Mode:  0644,
 				UID:   uint32(1000 + (i % 10)),
@@ -464,6 +474,7 @@ func TestQueryInjection(t *testing.T) {
 			file := &File{
 				Path:  types.FilePath(injection),
 				MTime: time.Now(),
+				CTime: time.Now(),
 				Size:  1024,
 				Mode:  0644,
 				UID:   1000,
@@ -502,6 +513,7 @@ func TestTimezoneHandling(t *testing.T) {
 	file := &File{
 		Path:  "/timezone-test.txt",
 		MTime: nyTime,
+		CTime: nyTime,
 		Size:  1024,
 		Mode:  0644,
 		UID:   1000,

internal/database/schema.sql

@@ -8,6 +8,7 @@ CREATE TABLE IF NOT EXISTS files (
     path TEXT NOT NULL UNIQUE,
     source_path TEXT NOT NULL DEFAULT '',  -- The source directory this file came from (for restore path stripping)
     mtime INTEGER NOT NULL,
+    ctime INTEGER NOT NULL,
     size INTEGER NOT NULL,
     mode INTEGER NOT NULL,
     uid INTEGER NOT NULL,

internal/snapshot/backup_test.go

@@ -345,8 +345,9 @@ func (b *BackupEngine) Backup(ctx context.Context, fsys fs.FS, root string) (str
 			Size:  info.Size(),
 			Mode:  uint32(info.Mode()),
 			MTime: info.ModTime(),
-			UID:   1000, // Default UID for test
-			GID:   1000, // Default GID for test
+			CTime: info.ModTime(), // Use mtime as ctime for test
+			UID:   1000,           // Default UID for test
+			GID:   1000,           // Default GID for test
 		}
 		err = b.repos.WithTx(ctx, func(ctx context.Context, tx *sql.Tx) error {
 			return b.repos.Files.Create(ctx, tx, file)

internal/snapshot/scanner.go

@@ -785,6 +785,7 @@ func (s *Scanner) checkFileInMemory(path string, info os.FileInfo, knownFiles ma
 		Path:       types.FilePath(path),
 		SourcePath: types.SourcePath(s.currentSourcePath), // Store source directory for restore path stripping
 		MTime:      info.ModTime(),
+		CTime:      info.ModTime(), // afero doesn't provide ctime
 		Size:       info.Size(),
 		Mode:       uint32(info.Mode()),
 		UID:        uid,

internal/vaultik/snapshot.go

@@ -988,6 +988,7 @@ func (v *Vaultik) listAllRemoteSnapshotIDs() ([]string, error) {
 	log.Info("Listing all snapshots")
 	objectCh := v.Storage.ListStream(v.ctx, "metadata/")
 
+	seen := make(map[string]bool)
 	var snapshotIDs []string
 	for object := range objectCh {
 		if object.Err != nil {
@@ -1002,14 +1003,8 @@ func (v *Vaultik) listAllRemoteSnapshotIDs() ([]string, error) {
 			}
 			if strings.HasSuffix(object.Key, "/") || strings.Contains(object.Key, "/manifest.json.zst") {
 				sid := parts[1]
-				found := false
-				for _, id := range snapshotIDs {
-					if id == sid {
-						found = true
-						break
-					}
-				}
-				if !found {
+				if !seen[sid] {
+					seen[sid] = true
 					snapshotIDs = append(snapshotIDs, sid)
 				}
 			}