Add scratch space for diff_outputs

src/function/diff_outputs.rs

@@ -1,28 +1,30 @@
 use super::{memo::Memo, Configuration, IngredientImpl};
 use crate::{
-    hash::FxHashSet, key::OutputDependencyIndex, zalsa::Zalsa, zalsa_local::QueryRevisions,
+    key::OutputDependencyIndex, plumbing::ZalsaLocal, zalsa::Zalsa, zalsa_local::QueryRevisions,
     AsDynDatabase as _, Database, DatabaseKeyIndex, Event, EventKind,
 };
 
 impl<C> IngredientImpl<C>
 where
     C: Configuration,
 {
-    /// Compute the old and new outputs and invoke the `clear_stale_output` callback
+    /// Compute the old and new outputs and invoke the `remove_stale_output` callback
     /// for each output that was generated before but is not generated now.
     ///
     /// This function takes a `&mut` reference to `revisions` to remove outputs
     /// that no longer exist in this revision from [`QueryRevisions::tracked_struct_ids`].
     pub(super) fn diff_outputs(
         &self,
         zalsa: &Zalsa,
+        zalsa_local: &ZalsaLocal,
         db: &C::DbView,
         key: DatabaseKeyIndex,
         old_memo: &Memo<C::Output<'_>>,
         revisions: &mut QueryRevisions,
     ) {
         // Iterate over the outputs of the `old_memo` and put them into a hashset
-        let mut old_outputs: FxHashSet<_> = old_memo.revisions.origin.outputs().collect();
+        let old_outputs = &mut *zalsa_local.diff_outputs_scratch.borrow_mut();
+        old_outputs.extend(old_memo.revisions.origin.outputs());
 
         // Iterate over the outputs of the current query
         // and remove elements from `old_outputs` when we find them
@@ -38,7 +40,7 @@ where
             });
         }
 
-        for old_output in old_outputs {
+        for old_output in old_outputs.drain() {
             Self::report_stale_output(zalsa, db, key, old_output);
         }
     }

src/function/execute.rs

@@ -79,7 +79,14 @@ where
         // old value.
         if let Some(old_memo) = &opt_old_memo {
             self.backdate_if_appropriate(old_memo, &mut revisions, &value);
-            self.diff_outputs(zalsa, db, database_key_index, old_memo, &mut revisions);
+            self.diff_outputs(
+                zalsa,
+                db.zalsa_local(),
+                db,
+                database_key_index,
+                old_memo,
+                &mut revisions,
+            );
         }
 
         tracing::debug!("{database_key_index:?}: read_upgrade: result.revisions = {revisions:#?}");

src/function/specify.rs

@@ -76,7 +76,14 @@ where
         let memo_ingredient_index = self.memo_ingredient_index(zalsa, key);
         if let Some(old_memo) = self.get_memo_from_table_for(zalsa, key, memo_ingredient_index) {
             self.backdate_if_appropriate(&old_memo, &mut revisions, &value);
-            self.diff_outputs(zalsa, db, database_key_index, &old_memo, &mut revisions);
+            self.diff_outputs(
+                zalsa,
+                zalsa_local,
+                db,
+                database_key_index,
+                &old_memo,
+                &mut revisions,
+            );
         }
 
         let memo = Memo {

src/zalsa_local.rs

@@ -6,6 +6,7 @@ use crate::accumulator::accumulated_map::{
 };
 use crate::active_query::ActiveQuery;
 use crate::durability::Durability;
+use crate::hash::FxHashSet;
 use crate::key::{DatabaseKeyIndex, InputDependencyIndex, OutputDependencyIndex};
 use crate::runtime::StampedValue;
 use crate::table::PageIndex;
@@ -36,13 +37,15 @@ pub struct ZalsaLocal {
     /// Stores the most recent page for a given ingredient.
     /// This is thread-local to avoid contention.
     most_recent_pages: RefCell<FxHashMap<IngredientIndex, PageIndex>>,
+    pub(crate) diff_outputs_scratch: RefCell<FxHashSet<OutputDependencyIndex>>,
 }
 
 impl ZalsaLocal {
     pub(crate) fn new() -> Self {
         ZalsaLocal {
-            query_stack: RefCell::new(vec![]),
-            most_recent_pages: RefCell::new(FxHashMap::default()),
+            query_stack: RefCell::default(),
+            most_recent_pages: RefCell::default(),
+            diff_outputs_scratch: RefCell::default(),
         }
     }