From 11a0e401ee881754fda784eb8a2edc3f35478dd5 Mon Sep 17 00:00:00 2001
From: Andy Dixon <andy@andydixon.com>
Date: Fri, 2 Oct 2026 08:40:10 +0100
Subject: [PATCH] Evaluate path predicates incrementally from cached directory
 paths

---
 PERFORMANCE.md           |  6 +++---
 ROADMAP.md               |  2 +-
 internal/filter/apply.go |  9 ++++++++-
 internal/filter/eval.go  | 26 +++++++++++++++++++++-----
 4 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/PERFORMANCE.md b/PERFORMANCE.md
index e34a09a..20438c7 100644
--- a/PERFORMANCE.md
+++ b/PERFORMANCE.md
@@ -95,15 +95,15 @@ once per rendered frame, so a resize storm cannot queue up work.
 |---|---:|
 | `size > 1MB` | 31 ms |
 | `*.dat AND size > 500k` | 119 ms |
-| `path contains sub3` (reconstructs every path) | 244 ms |
+| `path contains sub3` | 112 ms |
 
 Filters run on a background goroutine with cancellation and a 120 ms
 keystroke debounce; the UI never waits for them.
 
 ## Known costs / future work
 
-* Path predicates rebuild each node's path; an incremental evaluation along
-  the tree would make them ~10× cheaper.
+* Path predicates now build each path from the cached parent directory path
+  (244 ms → 112 ms); globs are dominated by `filepath.Match`.
 * Node records could shrink (owner/group/mode/link count are only needed for
   display and some filters) if memory on 10 M+ entry trees matters.
 * Cold-cache HDD benchmarks still need to be run with root access.
diff --git a/ROADMAP.md b/ROADMAP.md
index 4fa3d32..5457a73 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -43,7 +43,7 @@ Status markers: `[x]` done, `[~]` partial, `[ ]` not started.
 - [ ] Windows allocated-size via GetCompressedFileSizeW (opt-in)
 - [ ] configurable keybindings
 - [ ] cold-cache HDD scan benchmarks (need root to drop caches)
-- [ ] incremental path-predicate evaluation for filters
+- [x] incremental path-predicate evaluation for filters
 - [ ] permanent deletion (deliberately not offered yet; trash only)
 
 ## 1.0
diff --git a/internal/filter/apply.go b/internal/filter/apply.go
index e405abe..3650325 100644
--- a/internal/filter/apply.go
+++ b/internal/filter/apply.go
@@ -43,13 +43,20 @@ func Apply(ctx context.Context, t *inventory.Tree, q *Query, m inventory.SizeMod
 	r := &Result{Query: q, Mode: m, Sizes: make([]int64, n), Matched: make([]bool, n)}
 	covered := make([]bool, n)
 	c := &Ctx{Tree: t, Now: time.Now().UnixNano()}
+	if q.UsesPath {
+		c.dirPaths = map[inventory.NodeID]string{}
+	}
 	for i := range n {
 		if i&0xffff == 0 && ctx.Err() != nil {
 			return nil, ctx.Err()
 		}
 		id := inventory.NodeID(i)
 		nd := t.Node(id)
-		c.ID, c.Node = id, nd
+		c.ID, c.Node, c.path = id, nd, ""
+		if c.dirPaths != nil && nd.IsDir() {
+			c.path = c.lowerPath()
+			c.dirPaths[id] = c.path
+		}
 		if i > 0 && q.Match(c) {
 			r.Matched[i] = true
 			covered[i] = true
diff --git a/internal/filter/eval.go b/internal/filter/eval.go
index e04cc94..cdda783 100644
--- a/internal/filter/eval.go
+++ b/internal/filter/eval.go
@@ -16,6 +16,9 @@ type Ctx struct {
 	Node *inventory.Node
 	Now  int64 // unix nanoseconds
 	path string
+	// dirPaths caches lower-cased directory paths during Apply, which visits
+	// parents before children, so a node's path is one concatenation.
+	dirPaths map[inventory.NodeID]string
 }
 
 func (c *Ctx) str(f Field) string {
@@ -25,7 +28,7 @@ func (c *Ctx) str(f Field) string {
 		return strings.ToLower(n.Name)
 	case FPath:
 		if c.path == "" {
-			c.path = strings.ToLower(c.Tree.Path(c.ID))
+			c.path = c.lowerPath()
 		}
 		return c.path
 	case FExt:
@@ -62,6 +65,22 @@ func (c *Ctx) num(f Field) int64 {
 	return 0
 }
 
+func (c *Ctx) lowerPath() string {
+	if c.dirPaths != nil {
+		if p, ok := c.dirPaths[c.ID]; ok {
+			return p
+		}
+		if pp, ok := c.dirPaths[c.Node.Parent]; ok {
+			sep := string(filepath.Separator)
+			if strings.HasSuffix(pp, sep) {
+				sep = ""
+			}
+			return pp + sep + strings.ToLower(c.Node.Name)
+		}
+	}
+	return strings.ToLower(c.Tree.Path(c.ID))
+}
+
 type node interface{ eval(*Ctx) bool }
 
 type andNode struct{ l, r node }
@@ -154,7 +173,4 @@ func (n numNode) eval(c *Ctx) bool {
 }
 
 // Match evaluates the query against one node.
-func (q *Query) Match(c *Ctx) bool {
-	c.path = ""
-	return q.root.eval(c)
-}
+func (q *Query) Match(c *Ctx) bool { return q.root.eval(c) }