Revert "just walk active query stack once"

This reverts commit 2d79486.

Author: carljm

src/cycle.rs

@@ -119,16 +119,6 @@ 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;
@@ -144,10 +134,6 @@ 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

@@ -276,21 +276,18 @@ where
             "{database_key_index:?}: validate_same_iteration(memo = {memo:#?})",
             memo = memo.tracing_debug()
         );
-
-        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;
-                    }
-                }
+        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;
             }
-            false
-        })
+        }
+
+        true
     }
 
     /// VerifyResult::Unchanged if the memo's value and `changed_at` time is up-to-date in the