just walk active query stack once

Author: carljm

src/cycle.rs

@@ -119,6 +119,16 @@ impl CycleHeads {
             .any(|head| head.database_key_index == *value)
     }
 
+    pub(crate) fn contains_at_iteration(
+        &self,
+        database_key_index: DatabaseKeyIndex,
+        iteration_count: u32,
+    ) -> bool {
+        self.into_iter().any(|head| {
+            head.database_key_index == database_key_index && head.iteration_count == iteration_count
+        })
+    }
+
     pub(crate) fn remove(&mut self, value: &DatabaseKeyIndex) -> bool {
         let Some(cycle_heads) = &mut self.0 else {
             return false;
@@ -134,6 +144,10 @@ impl CycleHeads {
         true
     }
 
+    pub(crate) fn len(&self) -> usize {
+        self.0.as_ref().map(|heads| heads.len()).unwrap_or_default()
+    }
+
     pub(crate) fn update_iteration_count(
         &mut self,
         cycle_head_index: DatabaseKeyIndex,

src/function/maybe_changed_after.rs

@@ -276,18 +276,21 @@ where
             "{database_key_index:?}: validate_same_iteration(memo = {memo:#?})",
             memo = memo.tracing_debug()
         );
-        for cycle_head in &memo.revisions.cycle_heads {
-            if !db.zalsa_local().with_query_stack(|stack| {
-                stack.iter().any(|entry| {
-                    entry.database_key_index == cycle_head.database_key_index
-                        && entry.iteration_count == cycle_head.iteration_count
-                })
-            }) {
-                return false;
-            }
-        }
 
-        true
+        let heads = &memo.revisions.cycle_heads;
+        let num_heads = heads.len();
+        db.zalsa_local().with_query_stack(|stack| {
+            let mut found = 0;
+            for entry in stack.iter() {
+                if heads.contains_at_iteration(entry.database_key_index, entry.iteration_count) {
+                    found += 1;
+                    if found == num_heads {
+                        return true;
+                    }
+                }
+            }
+            false
+        })
     }
 
     /// VerifyResult::Unchanged if the memo's value and `changed_at` time is up-to-date in the