Merge pull request #3905 from DRON-666/haspaths-linear

Reduce quadratic time complexity of `Snapshot.HasPaths`

changelog/unreleased/pull-3905

@@ -0,0 +1,6 @@
+Enhancement: Improve speed of parent snapshot searching for `backup` command
+
+Backing up a large number of files using `--files-from-verbatim` or `--files-from-raw`
+options could require a long time to find the parent snapshot. This has been improved.
+
+https://github.com/restic/restic/pull/3905

internal/restic/snapshot.go

@@ -237,19 +237,14 @@ func (sn *Snapshot) HasTagList(l []TagList) bool {
 	return false
 }
 
-func (sn *Snapshot) hasPath(path string) bool {
-	for _, snPath := range sn.Paths {
-		if path == snPath {
-			return true
-		}
-	}
-	return false
-}
-
 // HasPaths returns true if the snapshot has all of the paths.
 func (sn *Snapshot) HasPaths(paths []string) bool {
+	m := make(map[string]struct{}, len(sn.Paths))
+	for _, snPath := range sn.Paths {
+		m[snPath] = struct{}{}
+	}
 	for _, path := range paths {
-		if !sn.hasPath(path) {
+		if _, ok := m[path]; !ok {
 			return false
 		}
 	}