Record each snapshot's new chunk size when its backup runs (closes #311)

snapshot list worked out NEW CHUNK SIZE from the snapshot's file rows. A
file's row is shared by every snapshot that lists it and rewritten when
the file changes, so a snapshot whose change was a modified file showed
0 B, and older snapshots' figures moved after later backups.

The scanner now totals the size of the chunks it stores that were not
stored before (the chunks chunk_count counts), the backup writes that
total to a new snapshots column, new_chunk_size, and snapshot list reads
it.

Judgement call: the figure is fixed when the backup runs, so removing an
earlier snapshot no longer raises a later snapshot's figure.

Model: opus-5-5

README.md

@@ -271,16 +271,8 @@ existing file. Created with mode `0600` since it will contain credentials.
 **`config set`**: Set a scalar config value by dotted YAML path
 (e.g. `vaultik config set compression_level 9`,
 `vaultik config set storage_url "file:///mnt/backups"`). Comments and
-formatting in the file are preserved. Missing keys along the path are
-created: as a list when the next path element is a number (so
-`vaultik config set age_recipients.0 age1...` works on a file without
-`age_recipients`), otherwise as a map. If the config loads, a change
-after which it would not, such as `vaultik config set compression_level 99`,
-is refused and the file is left unchanged. A config that does not load
-yet, such as the one `config init` writes before `storage_url` is set,
-can be filled in one setting at a time: only a change that gives a
-setting the wrong type, such as a single value where a list belongs or a
-word where a number belongs, is refused.
+formatting in the file are preserved; intermediate maps are created as
+needed.
 
 **`snapshot create`**: Perform incremental backup of configured snapshots.
 * Optional snapshot names argument to create specific snapshots (default: all)
@@ -301,8 +293,8 @@ word where a number belongs, is refused.
 **`snapshot list`**: Show every snapshot known to this host — the union
 of the local index and the backup destination store — with timestamps
 and three sizes per snapshot (compressed remote size; total
-uncompressed chunk size; size of chunks newly referenced by that
-snapshot).
+uncompressed chunk size; size of the chunks that snapshot stored that
+were not stored before, recorded when its backup ran).
 
 Listing the destination store does **not** require the age secret key,
 so it works in vaultik's intended configuration, where the backed-up
@@ -315,8 +307,8 @@ only the hash, so hostname and snapshot name exist solely in the local
 index and in the encrypted per-snapshot database. Snapshots found only
 on the destination store are therefore listed as
 `<remote only:<abbreviated remote key>>` and show `<remote only>` in
-the uncompressed and "new chunk" columns, which can only be computed
-from the local index. Their timestamp and compressed size are real,
+the uncompressed and "new chunk" columns, which come only from the
+local index. Their timestamp and compressed size are real,
 read from the manifest.
 
 Snapshots in the local index with no counterpart on the destination

docs/DATAMODEL.md

@@ -119,6 +119,7 @@ Tracks backup snapshots.
 - `completed_at` (INTEGER) - Completion timestamp (NULL if in progress)
 - `file_count` (INTEGER) - Number of files in snapshot
 - `chunk_count` (INTEGER) - Number of chunks this snapshot stored that were not stored before
+- `new_chunk_size` (INTEGER) - Total size of those chunks before compression; `snapshot list` shows it as NEW CHUNK SIZE
 - `blob_count` (INTEGER) - Number of blobs this snapshot created
 - `total_size` (INTEGER) - Total size of all files
 - `blob_size` (INTEGER) - Total compressed size of all referenced blobs

internal/cli/config.go

@@ -44,9 +44,6 @@ var (
 	errNeedNumericIndex = errors.New("key is a list; use a numeric index")
 	errIndexOutOfRange  = errors.New("index out of range")
 	errNotMapOrList     = errors.New("key is not a map or list")
-	errWouldNotLoad     = errors.New(
-		"vaultik would not load the config after this change, " +
-			"so the file was not changed")
 )
 
 const defaultConfigTemplate = `# vaultik configuration
@@ -394,15 +391,8 @@ func newConfigSetCommand() *cobra.Command {
 		Use:   "set <key> <value>",
 		Short: "Set a config value by dotted path (e.g. compression_level 5)",
 		Long: `Sets a scalar config value addressed by dotted YAML path and writes
-the file back, preserving comments and formatting. Missing keys along
-the path are created: as a list when the next path element is a
-number, otherwise as a map.
-
-If the config loads, a change after which it would not, such as
-compression_level 99, is refused and the file is left unchanged. A
-config that does not load yet, such as the one config init writes
-before storage_url is set, can be filled in one setting at a time:
-only a change that gives a setting the wrong type is refused.
+the file back, preserving comments and formatting. Intermediate maps
+are created as needed.
 
 Examples:
   vaultik config set storage_url "file:///mnt/backups"
@@ -432,11 +422,6 @@ func writeConfigSet(out *ui.Writer, path, key, value string) error {
 		return err
 	}
 
-	oldData, err := marshalConfigYAML(root)
-	if err != nil {
-		return fmt.Errorf("marshaling config: %w", err)
-	}
-
 	err = yamlPathSet(root, strings.Split(key, "."), value)
 	if err != nil {
 		return err
@@ -447,11 +432,6 @@ func writeConfigSet(out *ui.Writer, path, key, value string) error {
 		return fmt.Errorf("marshaling config: %w", err)
 	}
 
-	err = checkConfigChange(oldData, data)
-	if err != nil {
-		return fmt.Errorf("%w: %w", errWouldNotLoad, err)
-	}
-
 	err = os.WriteFile(path, data, configFileMode)
 	if err != nil {
 		return fmt.Errorf("writing config file: %w", err)
@@ -473,28 +453,6 @@ func writeConfigSet(out *ui.Writer, path, key, value string) error {
 	return nil
 }
 
-// checkConfigChange returns the reason vaultik would not load newData, the
-// config after a change, if the change brings that failure in. If oldData,
-// the config before it, decodes into the config type, the new one must
-// too; if the old one also passes validation, the new one must pass it. A
-// config still being filled in fails validation until it is complete, so
-// only decoding is checked for it.
-func checkConfigChange(oldData, newData []byte) error {
-	oldCfg, oldErr := config.Parse(oldData)
-	if oldErr == nil {
-		newCfg, err := config.Parse(newData)
-		if err != nil {
-			return err
-		}
-
-		if oldCfg.Validate() == nil {
-			return newCfg.Validate()
-		}
-	}
-
-	return nil
-}
-
 // marshalConfigYAML renders a config document tree with 2-space indentation,
 // matching defaultConfigTemplate. yaml.Marshal defaults to 4 spaces, which
 // would reindent the whole file on the first `config set` despite the promise
@@ -601,8 +559,8 @@ func yamlPathGet(root *yaml.Node, keys []string) (*yaml.Node, error) {
 	return node, nil
 }
 
-// yamlPathSet navigates a dotted key path, creating missing keys as needed,
-// and sets the final key to the given scalar value. Numeric path
+// yamlPathSet navigates a dotted key path, creating intermediate maps as
+// needed, and sets the final key to the given scalar value. Numeric path
 // components index into sequences; an index equal to the sequence length
 // appends a new element (e.g. "age_recipients.1" on a 1-element list).
 func yamlPathSet(root *yaml.Node, keys []string, value string) error {
@@ -615,12 +573,12 @@ func yamlPathSet(root *yaml.Node, keys []string, value string) error {
 		node = node.Content[0]
 	}
 
-	for i := range keys {
+	for i, key := range keys {
 		last := i == len(keys)-1
 
 		switch node.Kind {
 		case yaml.MappingNode:
-			node = yamlSetInMapping(node, keys, i, value, last)
+			node = yamlSetInMapping(node, key, value, last)
 		case yaml.SequenceNode:
 			next, err := yamlSetInSequence(node, keys, i, value, last)
 			if err != nil {
@@ -689,16 +647,14 @@ func yamlField(typ reflect.Type, key string) (reflect.StructField, bool) {
 	return reflect.StructField{}, false
 }
 
-// yamlSetInMapping resolves (creating if needed) the value node for the
-// path element keys[i] within a mapping node, setting it to value when it
-// is the final path element, and returns the node to descend into.
-func yamlSetInMapping(
-	node *yaml.Node, keys []string, i int, value string, last bool,
-) *yaml.Node {
+// yamlSetInMapping resolves (creating if needed) the value node for key
+// within a mapping node, setting it to value when it is the final path
+// element, and returns the node to descend into.
+func yamlSetInMapping(node *yaml.Node, key, value string, last bool) *yaml.Node {
 	var valueNode *yaml.Node
 
 	for j := 0; j+1 < len(node.Content); j += 2 {
-		if node.Content[j].Value == keys[i] {
+		if node.Content[j].Value == key {
 			valueNode = node.Content[j+1]
 
 			break
@@ -706,8 +662,13 @@ func yamlSetInMapping(
 	}
 
 	if valueNode == nil {
-		keyNode := &yaml.Node{Kind: yaml.ScalarNode, Value: keys[i]}
-		valueNode = newPathNode(keys, i, value)
+		keyNode := &yaml.Node{Kind: yaml.ScalarNode, Value: key}
+
+		valueNode = &yaml.Node{Kind: yaml.MappingNode}
+		if last {
+			valueNode = &yaml.Node{Kind: yaml.ScalarNode, Value: value}
+		}
+
 		node.Content = append(node.Content, keyNode, valueNode)
 	} else if last {
 		setScalar(valueNode, value)
@@ -735,7 +696,12 @@ func yamlSetInSequence(
 	}
 
 	if idx == len(node.Content) {
-		node.Content = append(node.Content, newPathNode(keys, i, value))
+		newNode := &yaml.Node{Kind: yaml.MappingNode}
+		if last {
+			newNode = &yaml.Node{Kind: yaml.ScalarNode, Value: value}
+		}
+
+		node.Content = append(node.Content, newNode)
 	} else if last {
 		setScalar(node.Content[idx], value)
 	}
@@ -743,22 +709,6 @@ func yamlSetInSequence(
 	return node.Content[idx], nil
 }
 
-// newPathNode returns the node to create for the missing path element
-// keys[i]: the value when it is the final path element, otherwise an empty
-// list when the next path element is a number and an empty map when not.
-func newPathNode(keys []string, i int, value string) *yaml.Node {
-	if i == len(keys)-1 {
-		return &yaml.Node{Kind: yaml.ScalarNode, Value: value}
-	}
-
-	_, err := strconv.Atoi(keys[i+1])
-	if err == nil {
-		return &yaml.Node{Kind: yaml.SequenceNode}
-	}
-
-	return &yaml.Node{Kind: yaml.MappingNode}
-}
-
 // setScalar overwrites a node in place with a plain scalar value.
 func setScalar(n *yaml.Node, value string) {
 	n.Kind = yaml.ScalarNode

internal/cli/config_test.go

@@ -58,16 +58,14 @@ func TestDefaultConfigTemplateParses(t *testing.T) {
 	}
 }
 
-// testRecipient is a valid age public key.
-const testRecipient = "age1278m9q7dp3chsh2dcy82qk27v047zywyvtxwnj4cvt0z65jw6a7q5dqhfj"
-
 // TestConfigSetRecipientOnFreshConfig follows the README quickstart: on the
 // file `config init` writes, `config set age_recipients.0` and
 // `config set storage_url` give a config that loads with that recipient.
-// Neither is refused, although the config does not load until both are set.
 func TestConfigSetRecipientOnFreshConfig(t *testing.T) {
 	t.Parallel()
 
+	const recipient = "age1278m9q7dp3chsh2dcy82qk27v047zywyvtxwnj4cvt0z65jw6a7q5dqhfj"
+
 	path := filepath.Join(t.TempDir(), "config.yml")
 
 	err := os.WriteFile(path, []byte(defaultConfigTemplate), configFileMode)
@@ -77,7 +75,7 @@ func TestConfigSetRecipientOnFreshConfig(t *testing.T) {
 
 	out := ui.NewWithColor(&bytes.Buffer{}, false)
 
-	err = writeConfigSet(out, path, "age_recipients.0", testRecipient)
+	err = writeConfigSet(out, path, "age_recipients.0", recipient)
 	if err != nil {
 		t.Fatalf("config set age_recipients.0: %v", err)
 	}
@@ -92,177 +90,8 @@ func TestConfigSetRecipientOnFreshConfig(t *testing.T) {
 		t.Fatalf("config.Load: %v", err)
 	}
 
-	if len(cfg.AgeRecipients) != 1 || cfg.AgeRecipients[0] != testRecipient {
-		t.Errorf("age_recipients = %v, want [%s]", cfg.AgeRecipients, testRecipient)
-	}
-}
-
-// configWithoutRecipients loads, but has no age_recipients key and no
-// snapshot named work.
-const configWithoutRecipients = `storage_url: file:///mnt/backups
-snapshots:
-  home:
-    paths:
-      - "~"
-`
-
-// TestConfigSetIndexUnderMissingKey checks that a list index under a key
-// the file does not have creates a list, and that the result loads.
-func TestConfigSetIndexUnderMissingKey(t *testing.T) {
-	t.Parallel()
-
-	tests := []struct {
-		key   string
-		value string
-		field func(cfg *config.Config) []string
-	}{
-		{"age_recipients.0", testRecipient,
-			func(cfg *config.Config) []string { return cfg.AgeRecipients }},
-		{"snapshots.work.paths.0", "/srv/work",
-			func(cfg *config.Config) []string { return cfg.Snapshots["work"].Paths }},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.key, func(t *testing.T) {
-			t.Parallel()
-
-			path := filepath.Join(t.TempDir(), "config.yml")
-
-			err := os.WriteFile(path, []byte(configWithoutRecipients), configFileMode)
-			if err != nil {
-				t.Fatalf("write config: %v", err)
-			}
-
-			err = writeConfigSet(ui.NewWithColor(&bytes.Buffer{}, false),
-				path, tt.key, tt.value)
-			if err != nil {
-				t.Fatalf("config set %s: %v", tt.key, err)
-			}
-
-			cfg, err := config.Load(path)
-			if err != nil {
-				t.Fatalf("config.Load: %v", err)
-			}
-
-			got := tt.field(cfg)
-			if len(got) != 1 || got[0] != tt.value {
-				t.Errorf("%s gives %v, want [%s]", tt.key, got, tt.value)
-			}
-		})
-	}
-}
-
-// TestConfigSetKeepsFileThatWouldNotLoad checks that config set refuses a
-// change after which the config would not load, with an error giving the
-// reason, and leaves the file as it was. On the file `config init` writes,
-// which does not load until storage_url is set, only a value of the wrong
-// type is refused.
-func TestConfigSetKeepsFileThatWouldNotLoad(t *testing.T) {
-	t.Parallel()
-
-	tests := []struct {
-		config string
-		key    string
-		value  string
-		reason string
-	}{
-		// Index 1 of the empty list the missing key gives.
-		{configWithoutRecipients, "age_recipients.1", testRecipient,
-			"index out of range"},
-		// A list set to a single value.
-		{configWithoutRecipients, "snapshots.home.paths", "/srv",
-			"cannot unmarshal"},
-		{configWithoutRecipients, "compression_level", "fast",
-			"cannot unmarshal"},
-		// Values of the right type that fail validation.
-		{configWithoutRecipients, "compression_level", "99",
-			"compression_level must be between 1 and 19"},
-		{configWithoutRecipients, "chunk_size", "1KB",
-			"chunk_size must be at least 1MB"},
-		{configWithoutRecipients, "age_recipients.0", "notakey",
-			"not a valid recipient"},
-		// The type check on a config that does not load yet.
-		{defaultConfigTemplate, "snapshots.apps.paths", "/srv",
-			"cannot unmarshal"},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.key+" "+tt.value, func(t *testing.T) {
-			t.Parallel()
-
-			path := filepath.Join(t.TempDir(), "config.yml")
-
-			err := os.WriteFile(path, []byte(tt.config), configFileMode)
-			if err != nil {
-				t.Fatalf("write config: %v", err)
-			}
-
-			err = writeConfigSet(ui.NewWithColor(&bytes.Buffer{}, false),
-				path, tt.key, tt.value)
-			if err == nil || !strings.Contains(err.Error(), tt.reason) {
-				t.Errorf("config set %s %s gives error %v, want one saying %q",
-					tt.key, tt.value, err, tt.reason)
-			}
-
-			data, err := os.ReadFile(path) //nolint:gosec // G304: test-controlled path
-			if err != nil {
-				t.Fatalf("read config: %v", err)
-			}
-
-			if string(data) != tt.config {
-				t.Errorf("config set %s changed the file to:\n%s",
-					tt.key, data)
-			}
-		})
-	}
-}
-
-// TestConfigSetRefusesOnlyItsOwnFailure checks that setting another key
-// works on a config with a ${...} reference on compression_level, which
-// loads because loading fills the reference in, and on one whose
-// compression_level already fails to load.
-func TestConfigSetRefusesOnlyItsOwnFailure(t *testing.T) {
-	t.Parallel()
-
-	levelPath := filepath.Join(t.TempDir(), "level")
-
-	err := os.WriteFile(levelPath, []byte("9"), configFileMode)
-	if err != nil {
-		t.Fatalf("write level: %v", err)
-	}
-
-	configs := map[string]string{
-		"reference": configWithoutRecipients +
-			"compression_level: ${FILE:" + levelPath + "}\n",
-		"failing": configWithoutRecipients + "compression_level: fast\n",
-	}
-
-	for name, configYAML := range configs {
-		t.Run(name, func(t *testing.T) {
-			t.Parallel()
-
-			path := filepath.Join(t.TempDir(), "config.yml")
-
-			err := os.WriteFile(path, []byte(configYAML), configFileMode)
-			if err != nil {
-				t.Fatalf("write config: %v", err)
-			}
-
-			err = writeConfigSet(ui.NewWithColor(&bytes.Buffer{}, false),
-				path, "hostname", "myhost")
-			if err != nil {
-				t.Fatalf("config set hostname: %v", err)
-			}
-
-			data, err := os.ReadFile(path) //nolint:gosec // G304: test-controlled path
-			if err != nil {
-				t.Fatalf("read config: %v", err)
-			}
-
-			if !strings.Contains(string(data), "hostname: myhost") {
-				t.Errorf("config set hostname wrote:\n%s", data)
-			}
-		})
+	if len(cfg.AgeRecipients) != 1 || cfg.AgeRecipients[0] != recipient {
+		t.Errorf("age_recipients = %v, want [%s]", cfg.AgeRecipients, recipient)
 	}
 }
 

internal/config/config.go

@@ -4,7 +4,6 @@
 package config
 
 import (
-	"bytes"
 	"errors"
 	"fmt"
 	"os"
@@ -234,48 +233,14 @@ func New(path Path) (*Config, error) {
 	return cfg, nil
 }
 
-// Load reads the configuration file at path, parses it with Parse, warns
-// when others can read the file, and validates the configuration.
-// Returns an error if the file cannot be read, parsed, or if validation
-// fails.
+// Load reads and parses the configuration file from the specified path.
+// It applies default values for optional fields, performs environment variable
+// substitution using smartconfig, and validates the configuration.
+// The configuration file should be in YAML format. Returns an error if the file
+// cannot be read, parsed, or if validation fails.
 func Load(path string) (*Config, error) {
-	data, err := os.ReadFile(path) //nolint:gosec // G304: config path is operator-supplied
-	if err != nil {
-		return nil, fmt.Errorf("failed to load config file: %w", err)
-	}
-
-	cfg, err := Parse(data)
-	if err != nil {
-		return nil, err
-	}
-
-	// Check config file permissions (warn if world or group readable)
-	//nolint:gosec // G703: config path is operator-supplied by design
-	info, statErr := os.Stat(path)
-	if statErr == nil {
-		mode := info.Mode().Perm()
-		if mode&0044 != 0 { // group or world readable
-			log.Warn(cfg.readableByOthersWarning(),
-				"path", path,
-				"mode", fmt.Sprintf("%04o", mode),
-				"recommendation", "chmod 600 "+path)
-		}
-	}
-
-	err = cfg.Validate()
-	if err != nil {
-		return nil, fmt.Errorf("invalid config: %w", err)
-	}
-
-	return cfg, nil
-}
-
-// Parse reads YAML config data as Load does, without validating it. It
-// applies default values for optional fields, fills in ${...} references
-// using smartconfig, and expands ~ in paths.
-func Parse(data []byte) (*Config, error) {
 	// Load config using smartconfig for interpolation
-	sc, err := smartconfig.NewFromReader(bytes.NewReader(data))
+	sc, err := smartconfig.NewFromConfigPath(path)
 	if err != nil {
 		return nil, fmt.Errorf("failed to load config file: %w", err)
 	}
@@ -337,6 +302,24 @@ func Parse(data []byte) (*Config, error) {
 		cfg.S3.Region = "us-east-1"
 	}
 
+	// Check config file permissions (warn if world or group readable)
+	//nolint:gosec // G703: config path is operator-supplied by design
+	info, statErr := os.Stat(path)
+	if statErr == nil {
+		mode := info.Mode().Perm()
+		if mode&0044 != 0 { // group or world readable
+			log.Warn(cfg.readableByOthersWarning(),
+				"path", path,
+				"mode", fmt.Sprintf("%04o", mode),
+				"recommendation", "chmod 600 "+path)
+		}
+	}
+
+	err = cfg.Validate()
+	if err != nil {
+		return nil, fmt.Errorf("invalid config: %w", err)
+	}
+
 	return cfg, nil
 }
 

internal/database/schema/001.sql

@@ -86,6 +86,7 @@ CREATE TABLE IF NOT EXISTS snapshots (
     completed_at INTEGER,
     file_count INTEGER NOT NULL DEFAULT 0,
     chunk_count INTEGER NOT NULL DEFAULT 0,
+    new_chunk_size INTEGER NOT NULL DEFAULT 0,
     blob_count INTEGER NOT NULL DEFAULT 0,
     total_size INTEGER NOT NULL DEFAULT 0,
     blob_size INTEGER NOT NULL DEFAULT 0,

internal/database/snapshots.go

@@ -129,6 +129,7 @@ func (r *SnapshotRepository) UpdateExtendedStats(
 	compressionLevel int,
 	uploadBytes int64,
 	uploadDurationMs int64,
+	newChunkSize int64,
 ) error {
 	compressionRatio, err := r.extendedCompressionRatio(
 		ctx, tx, snapshotID, blobUncompressedSize,
@@ -143,18 +144,19 @@ func (r *SnapshotRepository) UpdateExtendedStats(
 		    compression_ratio = ?,
 		    compression_level = ?,
 		    upload_bytes = ?,
-		    upload_duration_ms = ?
+		    upload_duration_ms = ?,
+		    new_chunk_size = ?
 		WHERE id = ?
 	`
 
 	if tx != nil {
 		_, err = tx.ExecContext(ctx, query,
 			blobUncompressedSize, compressionRatio, compressionLevel,
-			uploadBytes, uploadDurationMs, snapshotID)
+			uploadBytes, uploadDurationMs, newChunkSize, snapshotID)
 	} else {
 		_, err = r.db.ExecWithLog(ctx, query,
 			blobUncompressedSize, compressionRatio, compressionLevel,
-			uploadBytes, uploadDurationMs, snapshotID)
+			uploadBytes, uploadDurationMs, newChunkSize, snapshotID)
 	}
 
 	if err != nil {
@@ -594,45 +596,24 @@ func (r *SnapshotRepository) GetSnapshotUncompressedChunkSize(
 	return totalSize, nil
 }
 
-// GetSnapshotNewChunkSize returns the sum of plaintext sizes of chunks that are
-// referenced by this snapshot but not by any earlier completed snapshot known to
-// the local database. The result is the marginal uncompressed data this snapshot
-// added to the dedup pool — i.e., the delta from prior snapshots.
+// GetSnapshotNewChunkSize returns the total plaintext size of the chunks the
+// snapshot's backup stored that were not stored before, as the backup
+// recorded it. It is not derived from the snapshot's files: a file's row is
+// shared by every snapshot that lists it and is rewritten when the file
+// changes, so it shows only the file's latest chunks.
 func (r *SnapshotRepository) GetSnapshotNewChunkSize(
 	ctx context.Context, snapshotID string,
 ) (int64, error) {
-	query := `
-		WITH this_snap_chunks AS (
-			SELECT DISTINCT fc.chunk_hash
-			FROM snapshot_files sf
-			JOIN file_chunks fc ON sf.file_id = fc.file_id
-			WHERE sf.snapshot_id = ?
-		),
-		prior_chunks AS (
-			SELECT DISTINCT fc.chunk_hash
-			FROM snapshots s
-			JOIN snapshot_files sf ON sf.snapshot_id = s.id
-			JOIN file_chunks fc ON fc.file_id = sf.file_id
-			WHERE s.completed_at IS NOT NULL
-			  AND s.id != ?
-			  AND s.started_at < (SELECT started_at FROM snapshots WHERE id = ?)
-		)
-		SELECT COALESCE(SUM(c.size), 0)
-		FROM chunks c
-		JOIN this_snap_chunks t ON c.chunk_hash = t.chunk_hash
-		WHERE c.chunk_hash NOT IN (SELECT chunk_hash FROM prior_chunks)
-	`
+	query := `SELECT new_chunk_size FROM snapshots WHERE id = ?`
 
-	var totalSize int64
+	var newChunkSize int64
 
-	err := r.db.conn.QueryRowContext(
-		ctx, query, snapshotID, snapshotID, snapshotID,
-	).Scan(&totalSize)
+	err := r.db.conn.QueryRowContext(ctx, query, snapshotID).Scan(&newChunkSize)
 	if err != nil {
 		return 0, fmt.Errorf("querying new chunk size: %w", err)
 	}
 
-	return totalSize, nil
+	return newChunkSize, nil
 }
 
 // GetIncompleteSnapshots returns all snapshots that haven't been completed

internal/snapshot/scanner.go

@@ -135,7 +135,9 @@ type ScannerConfig struct {
 // are counted per file: BytesScanned is the size of the new and changed
 // files, BytesSkipped that of the unchanged ones. FilesFailed counts the
 // new and changed files that phase 2 could not store; FilesScanned
-// includes them and BytesScanned does not.
+// includes them and BytesScanned does not. ChunksCreated counts the
+// chunks that were not already stored, and NewChunkSize is their total
+// size.
 type ScanResult struct {
 	FilesScanned   int
 	FilesSkipped   int
@@ -145,6 +147,7 @@ type ScanResult struct {
 	BytesSkipped   int64
 	BytesDeleted   int64
 	ChunksCreated  int
+	NewChunkSize   int64
 	BlobsCreated   int
 	BlobsUploaded  int
 	BytesUploaded  int64
@@ -1866,11 +1869,12 @@ func (s *Scanner) processFileStreaming(
 	return nil
 }
 
-// updateChunkStats counts a chunk that was not already stored. The scan
-// result's file counts, BytesScanned and BytesSkipped are not touched
-// here: the scan phase counts each file once.
+// updateChunkStats counts a chunk that was not already stored, and its
+// size. The scan result's file counts, BytesScanned and BytesSkipped are
+// not touched here: the scan phase counts each file once.
 func (s *Scanner) updateChunkStats(chunkSize int64, result *ScanResult) {
 	result.ChunksCreated++
+	result.NewChunkSize += chunkSize
 
 	if s.progress != nil {
 		s.progress.GetStats().ChunksCreated.Add(1)

internal/snapshot/snapshot.go

@@ -199,6 +199,7 @@ func (sm *SnapshotManager) UpdateSnapshotStatsExtended(
 			stats.CompressionLevel,
 			stats.BytesUploaded,
 			stats.UploadDurationMs,
+			stats.NewChunkSize,
 		)
 	})
 }
@@ -906,6 +907,7 @@ type ExtendedBackupStats struct {
 	BlobUncompressedSize int64 // Total uncompressed size of all referenced blobs
 	CompressionLevel     int   // Compression level used for this snapshot
 	UploadDurationMs     int64 // Total milliseconds spent uploading to S3
+	NewChunkSize         int64 // Total size of the chunks counted in ChunksCreated
 }
 
 // deleteOtherSnapshots deletes all snapshots except the current one

internal/vaultik/blob_fetch.go

@@ -103,8 +103,6 @@ func (v *Vaultik) FetchAndDecryptBlob(
 }
 
 // FetchBlob downloads a blob and returns a reader for the encrypted data.
-// The reader is closed as soon as ctx is cancelled, which ends a read
-// blocked inside it.
 func (v *Vaultik) FetchBlob(
 	ctx context.Context, blobHash string,
 ) (io.ReadCloser, error) {
@@ -122,47 +120,5 @@ func (v *Vaultik) FetchBlob(
 		return nil, fmt.Errorf("downloading blob %s: %w", shortHash(blobHash), err)
 	}
 
-	return newCloseOnCancelReader(ctx, rc), nil
-}
-
-// closeOnCancelReader closes the reader it wraps when ctx is cancelled.
-// Not every backend's reader stops on cancel by itself (the file
-// backend's does not), and a read stalled on a slow or hung source would
-// otherwise outlast the shutdown timeout, so the process would exit
-// before restore or deep verify removed its decrypted temporary files.
-type closeOnCancelReader struct {
-	io.ReadCloser
-
-	ctx  context.Context //nolint:containedctx // Read reports its error
-	stop func() bool
-}
-
-func newCloseOnCancelReader(
-	ctx context.Context, rc io.ReadCloser,
-) *closeOnCancelReader {
-	return &closeOnCancelReader{
-		ReadCloser: rc,
-		ctx:        ctx,
-		stop:       context.AfterFunc(ctx, func() { _ = rc.Close() }),
-	}
-}
-
-// Read returns the context's error, not the closed reader's, once ctx
-// has been cancelled.
-func (r *closeOnCancelReader) Read(p []byte) (int, error) {
-	n, err := r.ReadCloser.Read(p)
-	if err != nil && r.ctx.Err() != nil {
-		return n, r.ctx.Err()
-	}
-
-	return n, err
-}
-
-// Close closes the wrapped reader, unless the cancel already closed it.
-func (r *closeOnCancelReader) Close() error {
-	if !r.stop() {
-		return nil
-	}
-
-	return r.ReadCloser.Close()
+	return rc, nil
 }

internal/vaultik/new_chunk_size_test.go

@@ -0,0 +1,133 @@
+package vaultik_test
+
+import (
+	"bytes"
+	"context"
+	"maps"
+	"path/filepath"
+	"testing"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/vaultik/internal/chunker"
+	"sneak.berlin/go/vaultik/internal/database"
+	"sneak.berlin/go/vaultik/internal/log"
+	"sneak.berlin/go/vaultik/internal/storage"
+	"sneak.berlin/go/vaultik/internal/vaultik"
+)
+
+// TestNewChunkSizeOfChangedFileStaysFixed covers
+// https://git.eeqj.de/sneak/vaultik/issues/311. A backup whose only change
+// is a modified file lists the size of the chunks that change added as its
+// NEW CHUNK SIZE, and a later backup that changes the file again leaves
+// every earlier snapshot's figure as it was. The file's row in the local
+// index is shared by all three snapshots and rewritten by each backup.
+func TestNewChunkSizeOfChangedFileStaysFixed(t *testing.T) {
+	log.Initialize(log.Config{})
+	t.Parallel()
+
+	fs := afero.NewOsFs()
+	tempDir := t.TempDir()
+	dataDir := filepath.Join(tempDir, "src")
+	dbPath := filepath.Join(tempDir, "index.sqlite")
+	changedPath := filepath.Join(dataDir, "changed.bin")
+
+	ctx := context.Background()
+	files := writeFaultSourceTree(t, fs, dataDir)
+	cfg := changedFileConfig(dataDir, dbPath)
+
+	appendRandomBytes(t, fs, files, changedPath, appendedFileSize)
+
+	store, err := storage.NewFileStorer(filepath.Join(tempDir, "remote"))
+	require.NoError(t, err)
+
+	db, err := database.New(ctx, dbPath)
+	require.NoError(t, err)
+	t.Cleanup(func() { _ = db.Close() })
+
+	repos := database.NewRepositories(db)
+	v := newBackupVaultik(ctx, cfg, store, repos, db, fs)
+
+	require.NoError(t, backUp(v, "first"))
+
+	firstFiles := maps.Clone(files)
+	firstID := localSnapshotID(ctx, t, repos, "first")
+
+	appendRandomBytes(t, fs, files, changedPath, faultChunkSize)
+	require.NoError(t, backUp(v, "second"))
+
+	secondID := localSnapshotID(ctx, t, repos, "second")
+	secondAdded := sizeOfNewChunks(t, files, firstFiles)
+	require.Positive(t, secondAdded)
+	assert.Equal(t, secondAdded, listedNewChunkSizes(t, v)[secondID],
+		"the second snapshot must count the chunks the change added")
+
+	appendRandomBytes(t, fs, files, changedPath, faultChunkSize)
+	require.NoError(t, backUp(v, "third"))
+
+	sizes := listedNewChunkSizes(t, v)
+	assert.Equal(t, sizeOfNewChunks(t, firstFiles, nil), sizes[firstID],
+		"a later backup must not change the first snapshot's figure")
+	assert.Equal(t, secondAdded, sizes[secondID],
+		"a later backup must not change the second snapshot's figure")
+}
+
+// sizeOfNewChunks returns the total size of the distinct chunks of the
+// files in after that no file in before has, cut the way the backup cuts
+// them.
+func sizeOfNewChunks(t *testing.T, after, before map[string][]byte) int64 {
+	t.Helper()
+
+	known := make(map[string]bool)
+	for _, chunk := range chunksOf(t, before) {
+		known[chunk.Hash] = true
+	}
+
+	var total int64
+
+	for _, chunk := range chunksOf(t, after) {
+		if !known[chunk.Hash] {
+			known[chunk.Hash] = true
+			total += chunk.Size
+		}
+	}
+
+	return total
+}
+
+// chunksOf returns the chunks of every file in files.
+func chunksOf(t *testing.T, files map[string][]byte) []chunker.Chunk {
+	t.Helper()
+
+	c := chunker.NewChunker(faultChunkSize)
+
+	var all []chunker.Chunk
+
+	for _, content := range files {
+		chunks, err := c.ChunkReader(bytes.NewReader(content))
+		require.NoError(t, err)
+
+		all = append(all, chunks...)
+	}
+
+	return all
+}
+
+// listedNewChunkSizes runs `snapshot list --json` and returns each listed
+// snapshot's new_chunk_size by snapshot ID.
+func listedNewChunkSizes(t *testing.T, v *vaultik.Vaultik) map[string]int64 {
+	t.Helper()
+
+	var out bytes.Buffer
+
+	v.Stdout = &out
+	require.NoError(t, v.ListSnapshots(true))
+
+	sizes := make(map[string]int64)
+	for _, row := range decodeListJSON(t, out.String()) {
+		sizes[row.ID] = row.NewChunkSize
+	}
+
+	return sizes
+}

internal/vaultik/restore_interrupt_test.go

@@ -142,14 +142,14 @@ func TestRestoreCleansTempDirOnInterrupt(t *testing.T) {
 }
 
 // scratchEntries returns the vaultik blob-cache and snapshot-database
-// scratch entries (restore's and deep verify's) currently present in dir.
+// scratch entries currently present in dir.
 func scratchEntries(t *testing.T, dir string) []string {
 	t.Helper()
 
 	var matches []string
 
 	for _, pattern := range []string{
-		"vaultik-blobcache-*", "vaultik-restore-*", "vaultik-verify-*",
+		"vaultik-blobcache-*", "vaultik-restore-*",
 	} {
 		found, err := filepath.Glob(filepath.Join(dir, pattern))
 		require.NoError(t, err)
@@ -206,119 +206,3 @@ func TestRestoreSkipErrorsCancelDuringBlobDownload(t *testing.T) {
 	assert.NotContains(t, out.String(), srcPath,
 		"the cancel was reported as a failed file")
 }
-
-// stallingBlobStorer wraps a Storer so that every blob download hands
-// over the first half of the blob and then stalls, ignoring the context,
-// as a file:// blob on a hung USB stick or network share does. Only
-// closing the returned reader ends the stall.
-type stallingBlobStorer struct {
-	storage.Storer
-
-	once    sync.Once
-	stalled chan struct{}
-}
-
-func newStallingBlobStorer(inner storage.Storer) *stallingBlobStorer {
-	return &stallingBlobStorer{Storer: inner, stalled: make(chan struct{})}
-}
-
-func (s *stallingBlobStorer) Get(
-	ctx context.Context, key string,
-) (io.ReadCloser, error) {
-	rc, err := s.Storer.Get(ctx, key)
-	if err != nil || !strings.HasPrefix(key, "blobs/") {
-		return rc, err
-	}
-
-	blob, err := io.ReadAll(rc)
-	_ = rc.Close()
-
-	if err != nil {
-		return nil, err
-	}
-
-	// The writer is never closed, so once the first half has been read
-	// the next Read blocks until the reader is closed.
-	pr, pw := io.Pipe()
-
-	go func() {
-		_, _ = pw.Write(blob[:len(blob)/2])
-
-		s.once.Do(func() { close(s.stalled) })
-	}()
-
-	return pr, nil
-}
-
-// TestInterruptDuringStalledBlobReadCleansTempDir stops a restore and a
-// deep verify while a blob read is stalled on a source that ignores the
-// context. Stopping must end that read, so the operation unwinds and
-// removes its decrypted scratch files well within the shutdown timeout
-// (issue #325).
-//
-// Not parallel: it points TMPDIR at a private directory (via t.Setenv)
-// so it can assert on exactly the scratch files the operation created.
-func TestInterruptDuringStalledBlobReadCleansTempDir(t *testing.T) {
-	log.Initialize(log.Config{})
-
-	operations := map[string]func(v *Vaultik, snapshotID, targetDir string) error{
-		"restore": func(v *Vaultik, snapshotID, targetDir string) error {
-			return v.Restore(&RestoreOptions{
-				SnapshotID: snapshotID,
-				TargetDir:  targetDir,
-			})
-		},
-		"deep verify": func(v *Vaultik, snapshotID, _ string) error {
-			return v.RunDeepVerify(snapshotID, &VerifyOptions{Deep: true})
-		},
-	}
-
-	for name, op := range operations {
-		t.Run(name, func(t *testing.T) {
-			fs := afero.NewOsFs()
-			root := t.TempDir()
-
-			// Random content, so the blob stays large enough to stall
-			// part-way through its compressed, encrypted body.
-			cfg, storer, snapshotID, _ := backupOneFile(context.Background(),
-				t, fs, root, "a.bin", randomBytes(t, 256*1024), 0o644)
-
-			scratch := filepath.Join(root, "scratch")
-			require.NoError(t, fs.MkdirAll(scratch, 0o755))
-			t.Setenv("TMPDIR", scratch)
-
-			stalling := newStallingBlobStorer(storer)
-
-			ctx, cancel := context.WithCancel(context.Background())
-			defer cancel()
-
-			v := newRestoreVaultik(ctx, cfg, stalling, fs)
-			v.cancel = cancel
-
-			var opErr error
-
-			stop := v.StartOperation(func() {
-				opErr = op(v, snapshotID, filepath.Join(root, "restored"))
-			})
-
-			select {
-			case <-stalling.stalled:
-			case <-time.After(30 * time.Second):
-				t.Fatal("the operation never reached a blob read")
-			}
-
-			require.NotEmpty(t, scratchEntries(t, scratch),
-				"expected decrypted scratch files to exist mid-read")
-
-			stopCtx, stopCancel := context.WithTimeout(
-				context.Background(), 10*time.Second)
-			defer stopCancel()
-
-			require.True(t, stop(stopCtx),
-				"stop timed out; the stalled blob read was not interrupted")
-			require.ErrorIs(t, opErr, context.Canceled)
-			require.Empty(t, scratchEntries(t, scratch),
-				"decrypted scratch files remained after the interrupt")
-		})
-	}
-}

internal/vaultik/snapshot.go

@@ -209,6 +209,7 @@ type snapshotStats struct {
 	totalFiles         int
 	totalBytes         int64
 	totalChunks        int
+	newChunkSize       int64
 	totalBlobs         int
 	totalBytesSkipped  int64
 	totalFilesSkipped  int
@@ -341,6 +342,7 @@ func (v *Vaultik) scanAllDirectories(
 		stats.totalFiles += result.FilesScanned
 		stats.totalBytes += result.BytesScanned
 		stats.totalChunks += result.ChunksCreated
+		stats.newChunkSize += result.NewChunkSize
 		stats.totalBlobs += result.BlobsCreated
 		stats.totalFilesSkipped += result.FilesSkipped
 		stats.totalFilesFailed += result.FilesFailed
@@ -403,6 +405,7 @@ func (v *Vaultik) finalizeSnapshotMetadata(
 		BlobUncompressedSize: stats.blobUncompressedSize,
 		CompressionLevel:     v.Config.CompressionLevel,
 		UploadDurationMs:     stats.uploadDuration.Milliseconds(),
+		NewChunkSize:         stats.newChunkSize,
 	}
 
 	err = v.SnapshotManager.UpdateSnapshotStatsExtended(v.ctx, snapshotID, extStats)

internal/vaultik/snapshot_list_test.go

@@ -445,6 +445,7 @@ type listJSONRow struct {
 	RemoteKey      string `json:"remote_key"`
 	Timestamp      string `json:"timestamp"`
 	CompressedSize int64  `json:"compressed_size"`
+	NewChunkSize   int64  `json:"new_chunk_size"`
 	LocallyTracked bool   `json:"locally_tracked"`
 	RemotePresent  *bool  `json:"remote_present"`
 }