eval_updates_sequential: no queries? => quit early

crates/core/src/subscription/module_subscription_manager.rs

@@ -1146,11 +1146,44 @@ impl SubscriptionManager {
         event: Arc<ModuleEvent>,
         caller: Option<Arc<ClientConnectionSender>>,
     ) -> ExecutionMetrics {
-        use FormatSwitch::{Bsatn, Json};
+        let span = tracing::info_span!("eval_incr").entered();
 
-        let tables = &event.status.database_update().unwrap().tables;
+        let (updates, errs, metrics) = if self.queries.is_empty() {
+            // We have no queries, so do nothing.
+            <_>::default()
+        } else {
+            let tables = &event.status.database_update().unwrap().tables;
+            self.eval_updates_sequential_inner(tx, bsatn_rlb_pool, tables)
+        };
 
-        let span = tracing::info_span!("eval_incr").entered();
+        let queries = ComputedQueries {
+            updates,
+            errs,
+            event,
+            caller,
+        };
+
+        // We've now finished all of the work which needs to read from the datastore,
+        // so get this work off the main thread and over to the `send_worker`,
+        // then return ASAP in order to unlock the datastore and start running the next transaction.
+        // See comment on the `send_worker_tx` field in [`SubscriptionManager`] for more motivation.
+        self.send_worker_queue
+            .send(SendWorkerMessage::Broadcast { tx_offset, queries })
+            .expect("send worker has panicked, or otherwise dropped its recv queue!");
+
+        drop(span);
+
+        metrics
+    }
+
+    #[allow(clippy::type_complexity)]
+    fn eval_updates_sequential_inner(
+        &self,
+        tx: &DeltaTx,
+        bsatn_rlb_pool: &BsatnRowListBuilderPool,
+        tables: &[DatabaseTableUpdate],
+    ) -> (Vec<ClientUpdate>, Vec<(ClientId, Box<str>)>, ExecutionMetrics) {
+        use FormatSwitch::{Bsatn, Json};
 
         #[derive(Default)]
         struct FoldState {
@@ -1306,25 +1339,7 @@ impl SubscriptionManager {
                 acc
             });
 
-        // We've now finished all of the work which needs to read from the datastore,
-        // so get this work off the main thread and over to the `send_worker`,
-        // then return ASAP in order to unlock the datastore and start running the next transaction.
-        // See comment on the `send_worker_tx` field in [`SubscriptionManager`] for more motivation.
-        self.send_worker_queue
-            .send(SendWorkerMessage::Broadcast {
-                tx_offset,
-                queries: ComputedQueries {
-                    updates,
-                    errs,
-                    event,
-                    caller,
-                },
-            })
-            .expect("send worker has panicked, or otherwise dropped its recv queue!");
-
-        drop(span);
-
-        metrics
+        (updates, errs, metrics)
     }
 }