diff --git a/cozo-core/benches/pokec.rs b/cozo-core/benches/pokec.rs
index 48922f4a..0ba14bcc 100644
--- a/cozo-core/benches/pokec.rs
+++ b/cozo-core/benches/pokec.rs
@@ -195,12 +195,8 @@ const READ_QUERIES: [QueryFn; 1] = [single_vertex];
 const WRITE_QUERIES: [QueryFn; 2] = [single_edge_write, single_vertex_write];
 const UPDATE_QUERIES: [QueryFn; 1] = [single_vertex_update];
 #[allow(dead_code)]
-const AGGREGATE_QUERIES: [QueryFn; 4] = [
-    aggregation,
-    aggregation_filter,
-    aggregation_count,
-    min_max,
-];
+const AGGREGATE_QUERIES: [QueryFn; 4] =
+    [aggregation, aggregation_filter, aggregation_count, min_max];
 const ANALYTICAL_QUERIES: [QueryFn; 15] = [
     expansion_1,
     expansion_2,
@@ -294,7 +290,10 @@ fn aggregation() {
 
 fn aggregation_count() {
     TEST_DB
-        .run_script("?[count(uid), count(age)] := *user{uid, age}", Default::default())
+        .run_script(
+            "?[count(uid), count(age)] := *user{uid, age}",
+            Default::default(),
+        )
         .unwrap();
 }
 
@@ -1017,4 +1016,10 @@ fn mixed(_: &mut Bencher) {
         wrap(mixed_pct, single_vertex);
     });
     dbg!((count as f64) / single_vertex_time.elapsed().as_secs_f64());
+
+    let single_vertex_update_time = Instant::now();
+    (0..count).into_par_iter().for_each(|_| {
+        wrap(mixed_pct, single_vertex_update);
+    });
+    dbg!((count as f64) / single_vertex_update_time.elapsed().as_secs_f64());
 }
diff --git a/cozo-core/src/query/eval.rs b/cozo-core/src/query/eval.rs
index 73dc3987..0527c34d 100644
--- a/cozo-core/src/query/eval.rs
+++ b/cozo-core/src/query/eval.rs
@@ -118,6 +118,10 @@ impl<'a> SessionTx<'a> {
                     }
                 }
             } else {
+                for store in stores.values() {
+                    store.ensure_mem_db_for_epoch(epoch);
+                }
+
                 mem::swap(&mut changed, &mut prev_changed);
                 for (_k, v) in changed.iter_mut() {
                     *v = false;
diff --git a/cozo-core/src/runtime/in_mem.rs b/cozo-core/src/runtime/in_mem.rs
index 4326fae4..5405953c 100644
--- a/cozo-core/src/runtime/in_mem.rs
+++ b/cozo-core/src/runtime/in_mem.rs
@@ -60,7 +60,7 @@ impl InMemRelation {
             arity,
         }
     }
-    fn ensure_mem_db_for_epoch(&self, epoch: u32) {
+    pub(crate) fn ensure_mem_db_for_epoch(&self, epoch: u32) {
         if self.epoch_size.load(Ordering::Relaxed) > epoch {
             return;
         }
@@ -84,10 +84,9 @@ impl InMemRelation {
         aggrs: &mut [Option<(Aggregation, Vec<DataValue>)>],
         epoch: u32,
     ) -> Result<bool> {
-        self.ensure_mem_db_for_epoch(epoch);
-
         let mem_db: &RefCell<_> = self.mem_db.borrow();
-        let zero_map = mem_db.borrow().get(0).unwrap().clone();
+        let zero_maps = mem_db.borrow();
+        let zero_map = zero_maps.get(0).unwrap();
 
         let zero_target: &RefCell<BTreeMap<_, _>> = zero_map.borrow();
         let mut zero_target = zero_target.borrow_mut();
@@ -116,7 +115,8 @@ impl InMemRelation {
                 }
             }
             if changed && epoch != 0 {
-                let epoch_map = mem_db.borrow().get(epoch as usize).unwrap().clone();
+                let epoch_maps = mem_db.borrow();
+                let epoch_map = epoch_maps.get(epoch as usize).unwrap();
                 let epoch_map: &RefCell<BTreeMap<_, _>> = epoch_map.borrow();
                 let mut epoch_map = epoch_map.borrow_mut();
                 epoch_map.insert(key, prev_aggr.clone());
@@ -138,7 +138,8 @@ impl InMemRelation {
             );
             zero_target.insert(key.clone(), tuple_to_store.clone());
             if epoch != 0 {
-                let epoch_map = mem_db.borrow().get(epoch as usize).unwrap().clone();
+                let epoch_maps = mem_db.borrow();
+                let epoch_map = epoch_maps.get(epoch as usize).unwrap();
                 let epoch_map: &RefCell<BTreeMap<_, _>> = epoch_map.borrow();
                 let mut epoch_map = epoch_map.borrow_mut();
                 epoch_map.insert(key, tuple_to_store);
@@ -147,17 +148,17 @@ impl InMemRelation {
         }
     }
     pub(crate) fn put(&self, tuple: Tuple, epoch: u32) {
-        self.ensure_mem_db_for_epoch(epoch);
         let mem_db: &RefCell<_> = self.mem_db.borrow();
-        let epoch_map = mem_db.borrow().get(epoch as usize).unwrap().clone();
+        let epoch_maps = mem_db.borrow();
+        let epoch_map = epoch_maps.get(epoch as usize).unwrap();
         let epoch_map: &RefCell<BTreeMap<_, _>> = epoch_map.borrow();
         let mut epoch_map = epoch_map.borrow_mut();
         epoch_map.insert(tuple, Tuple::default());
     }
     pub(crate) fn put_with_skip(&self, tuple: Tuple, should_skip: bool) {
-        self.ensure_mem_db_for_epoch(0);
         let mem_db: &RefCell<_> = self.mem_db.borrow();
-        let epoch_map = mem_db.borrow().get(0).unwrap().clone();
+        let epoch_maps = mem_db.borrow();
+        let epoch_map = epoch_maps.get(0).unwrap();
         let epoch_map: &RefCell<BTreeMap<_, _>> = epoch_map.borrow();
         let mut epoch_map = epoch_map.borrow_mut();
 
@@ -168,9 +169,9 @@ impl InMemRelation {
         }
     }
     pub(crate) fn exists(&self, tuple: &Tuple, epoch: u32) -> bool {
-        self.ensure_mem_db_for_epoch(epoch);
         let mem_db: &RefCell<_> = self.mem_db.borrow();
-        let epoch_map = mem_db.borrow().get(epoch as usize).unwrap().clone();
+        let epoch_maps = mem_db.borrow();
+        let epoch_map = epoch_maps.get(epoch as usize).unwrap();
         let epoch_map: &RefCell<BTreeMap<_, _>> = epoch_map.borrow();
         let epoch_map = epoch_map.borrow();
 
@@ -181,12 +182,13 @@ impl InMemRelation {
         &'a self,
         epoch: u32,
     ) -> impl Iterator<Item = Result<Tuple>> + 'a {
-        self.ensure_mem_db_for_epoch(epoch);
         let mem_db: &RefCell<_> = self.mem_db.borrow();
-        let epoch_map = mem_db.borrow().get(epoch as usize).unwrap().clone();
+        let epoch_maps = mem_db.borrow();
+        let epoch_map = epoch_maps.get(epoch as usize).unwrap();
         let epoch_map: &RefCell<BTreeMap<_, _>> = epoch_map.borrow();
         let epoch_map = epoch_map.borrow();
 
+        // FIXME
         epoch_map.clone().into_iter().map(|(k, v)| {
             if v.0.is_empty() {
                 Ok(k)
@@ -210,12 +212,13 @@ impl InMemRelation {
         self.scan_all_for_epoch(0)
     }
     pub(crate) fn scan_early_returned<'a>(&'a self) -> impl Iterator<Item = Result<Tuple>> + 'a {
-        self.ensure_mem_db_for_epoch(0);
         let mem_db: &RefCell<_> = self.mem_db.borrow();
-        let epoch_map = mem_db.borrow().get(0).unwrap().clone();
+        let epoch_maps = mem_db.borrow();
+        let epoch_map = epoch_maps.get(0).unwrap();
         let epoch_map: &RefCell<BTreeMap<_, _>> = epoch_map.borrow();
         let epoch_map = epoch_map.borrow();
 
+        // FIXME
         epoch_map.clone().into_iter().filter_map(|(k, v)| {
             if v.0.is_empty() {
                 Some(Ok(k))
@@ -248,9 +251,9 @@ impl InMemRelation {
         let mut upper = prefix.0.clone();
         upper.push(DataValue::Bot);
         let upper = Tuple(upper);
-        self.ensure_mem_db_for_epoch(epoch);
         let mem_db: &RefCell<_> = self.mem_db.borrow();
-        let epoch_map = mem_db.borrow().get(epoch as usize).unwrap().clone();
+        let epoch_maps = mem_db.borrow();
+        let epoch_map = epoch_maps.get(epoch as usize).unwrap();
         let epoch_map: &RefCell<BTreeMap<_, _>> = epoch_map.borrow();
         let epoch_map = epoch_map.borrow();
 
@@ -284,14 +287,14 @@ impl InMemRelation {
         upper: &[DataValue],
         epoch: u32,
     ) -> impl Iterator<Item = Result<Tuple>> {
-        self.ensure_mem_db_for_epoch(epoch);
         let mut prefix_bound = prefix.clone();
         prefix_bound.0.extend_from_slice(lower);
         let mut upper_bound = prefix.clone();
         upper_bound.0.extend_from_slice(upper);
 
         let mem_db: &RefCell<_> = self.mem_db.borrow();
-        let epoch_map = mem_db.borrow().get(epoch as usize).unwrap().clone();
+        let epoch_maps = mem_db.borrow();
+        let epoch_map = epoch_maps.get(epoch as usize).unwrap();
         let epoch_map: &RefCell<BTreeMap<_, _>> = epoch_map.borrow();
         let epoch_map = epoch_map.borrow();
 
diff --git a/cozo-core/src/runtime/transact.rs b/cozo-core/src/runtime/transact.rs
index 798904f6..73525ff4 100644
--- a/cozo-core/src/runtime/transact.rs
+++ b/cozo-core/src/runtime/transact.rs
@@ -30,19 +30,23 @@ impl<'a> SessionTx<'a> {
     pub(crate) fn new_rule_store(&self, rule_name: MagicSymbol, arity: usize) -> InMemRelation {
         let old_count = self.mem_store_id.fetch_add(1, Ordering::AcqRel);
         let old_count = old_count & 0x00ff_ffffu32;
-        InMemRelation::new(StoredRelationId(old_count), rule_name, arity)
+        let ret = InMemRelation::new(StoredRelationId(old_count), rule_name, arity);
+        ret.ensure_mem_db_for_epoch(0);
+        ret
     }
 
     pub(crate) fn new_temp_store(&self, span: SourceSpan) -> InMemRelation {
         let old_count = self.mem_store_id.fetch_add(1, Ordering::AcqRel);
         let old_count = old_count & 0x00ff_ffffu32;
-        InMemRelation::new(
+        let ret = InMemRelation::new(
             StoredRelationId(old_count),
             MagicSymbol::Muggle {
                 inner: Symbol::new("", span),
             },
             0,
-        )
+        );
+        ret.ensure_mem_db_for_epoch(0);
+        ret
     }
 
     pub(crate) fn load_last_relation_store_id(&self) -> Result<RelationId> {