v1.2.0: skip unchanged writes, transactional schema/root counters, snapshot replay for meta:events 0-0 (drops boot republish), collect-once search driver

internal/kv/kv_test.go

@@ -44,20 +44,21 @@ func events(t *testing.T, s *Store) []Entry {
 }
 
 // The replacement for keyspace notifications: a change and its event commit
-// together, with Redis' semantics — `set` even for an unchanged value, `del`
-// only for a key that existed, and nothing for keys outside the event scope.
+// together. `set` only for a real change (an unchanged value is a no-op: no
+// write, no event), `del` only for a key that existed, nothing for keys outside
+// the event scope.
 func TestChangesPublishEventsWithRedisSemantics(t *testing.T) {
 	s := openTest(t, "")
 	update(t, s, func(tx *Tx) error {
 		_ = tx.Put("file:A/title", "x")
-		_ = tx.Put("file:A/title", "x") // unchanged value still publishes
+		_ = tx.Put("file:A/title", "x") // unchanged: no write, no event
 		_ = tx.Put("cid:bafk", "A")     // outside the event scope
 		_, _ = tx.Delete("file:A/missing")
 		_, _ = tx.Delete("file:A/title")
 		return nil
 	})
 	got := events(t, s)
-	want := []string{"set file:A/title", "set file:A/title", "del file:A/title"}
+	want := []string{"set file:A/title", "del file:A/title"}
 	if len(got) != len(want) {
 		t.Fatalf("events = %+v, want %v", got, want)
 	}
@@ -312,3 +313,50 @@ func TestGroupCommitIsolatesFailures(t *testing.T) {
 		}
 	}
 }
+
+// The change hook sees real changes only, with old and new values, and
+// counters follow the request's fate (a failed request's deltas are dropped).
+func TestOnChangeAndCounters(t *testing.T) {
+	type change struct{ k, old, new string }
+	var seen []change
+	s, err := Open(filepath.Join(t.TempDir(), "kv.db"), Options{
+		OnChange: func(tx *Tx, k, old string, hadOld bool, v string, hasNew bool) {
+			seen = append(seen, change{k, old, v})
+			if hasNew {
+				tx.AddCounter("count/"+v, 1)
+			}
+			if hadOld {
+				tx.AddCounter("count/"+old, -1)
+			}
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer s.Close()
+	update(t, s, func(tx *Tx) error {
+		_ = tx.Put("a", "x")
+		_ = tx.Put("b", "x")
+		_ = tx.Put("a", "x") // no-op
+		_ = tx.Put("a", "y")
+		return nil
+	})
+	_ = s.Update(context.Background(), func(tx *Tx) error {
+		_ = tx.Put("c", "x")
+		return errors.New("fail")
+	})
+	update(t, s, func(tx *Tx) error { _, err := tx.DeletePrefix("b", 0); return err })
+
+	if len(seen) != 5 { // a=x, b=x, a x→y, c=x (rolled back, hook still ran), del b; stats count attempts
+		t.Fatalf("changes = %+v", seen)
+	}
+	for k, want := range map[string]int64{"count/x": 0, "count/y": 1} {
+		got, _, err := s.Counter(context.Background(), k)
+		if err != nil || got != want {
+			t.Errorf("%s = %d (err %v), want %d", k, got, err, want)
+		}
+	}
+	if changed, unchanged := s.WriteStats(); changed != 4 || unchanged != 1 {
+		t.Errorf("write stats = %d changed / %d unchanged", changed, unchanged)
+	}
+}