incremental: optimize build field plan

Replicates graphql/graphql-js@25be244

Author: Cito

src/graphql/execution/build_field_plan.py

@@ -34,48 +34,47 @@ def build_field_plan(
         parent_defer_usages = RefSet()
 
     grouped_field_set: GroupedFieldSet = {}
-
     new_grouped_field_sets: RefMap[DeferUsageSet, GroupedFieldSet] = RefMap()
 
-    map_: dict[str, tuple[DeferUsageSet, FieldGroup]] = {}
-
     for response_key, field_group in original_grouped_field_set.items():
-        defer_usage_set: RefSet[DeferUsage] = RefSet()
-        in_original_result = False
-        for field_details in field_group:
-            defer_usage = field_details.defer_usage
-            if defer_usage is None:
-                in_original_result = True
-                continue
-            defer_usage_set.add(defer_usage)
-        if in_original_result:
-            defer_usage_set.clear()
-        else:
-            defer_usage_set -= {
-                defer_usage
-                for defer_usage in defer_usage_set
-                if any(
-                    ancestor in defer_usage_set for ancestor in defer_usage.ancestors
-                )
-            }
-        map_[response_key] = (defer_usage_set, field_group)
-
-    for response_key, [defer_usage_set, field_group] in map_.items():
-        if defer_usage_set == parent_defer_usages:
+        filtered_defer_usage_set = get_filtered_defer_usage_set(field_group)
+
+        if filtered_defer_usage_set == parent_defer_usages:
             grouped_field_set[response_key] = field_group
             continue
 
-        for (
-            new_grouped_field_set_defer_usage_set,
-            new_grouped_field_set_field_group,
-        ) in new_grouped_field_sets.items():  # pragma: no branch
-            if new_grouped_field_set_defer_usage_set == defer_usage_set:
-                new_grouped_field_set = new_grouped_field_set_field_group
+        for defer_usage_set in new_grouped_field_sets:
+            if defer_usage_set == filtered_defer_usage_set:
+                new_grouped_field_set = new_grouped_field_sets[defer_usage_set]
                 break
         else:
             new_grouped_field_set = {}
-            new_grouped_field_sets[defer_usage_set] = new_grouped_field_set
+            new_grouped_field_sets[filtered_defer_usage_set] = new_grouped_field_set
 
         new_grouped_field_set[response_key] = field_group
 
     return FieldPlan(grouped_field_set, new_grouped_field_sets)
+
+
+def get_filtered_defer_usage_set(field_group: FieldGroup) -> RefSet[DeferUsage]:
+    """Get a filtered set of defer usages."""
+    # Create the set of defer usages for the field group.
+    filtered_defer_usage_set: RefSet[DeferUsage] = RefSet()
+    for field_details in field_group:
+        defer_usage = field_details.defer_usage
+        if defer_usage is None:
+            filtered_defer_usage_set.clear()
+            return filtered_defer_usage_set
+        filtered_defer_usage_set.add(defer_usage)
+
+    # Remove defer usages that have a parent defer usage in the set.
+    # Since we remove in place, we need to iterate over a copy of the set.
+    for defer_usage in tuple(filtered_defer_usage_set):
+        parent_defer_usage: DeferUsage | None = defer_usage.parent_defer_usage
+        while parent_defer_usage is not None:
+            if parent_defer_usage in filtered_defer_usage_set:
+                filtered_defer_usage_set.discard(defer_usage)
+                break
+            parent_defer_usage = parent_defer_usage.parent_defer_usage
+
+    return filtered_defer_usage_set

src/graphql/execution/collect_fields.py

@@ -43,16 +43,6 @@ class DeferUsage(NamedTuple):
     label: str | None
     parent_defer_usage: DeferUsage | None
 
-    @property
-    def ancestors(self) -> list[DeferUsage]:
-        """Get the ancestors of this defer usage."""
-        ancestors: list[DeferUsage] = []
-        parent_defer_usage = self.parent_defer_usage
-        while parent_defer_usage is not None:
-            ancestors.append(parent_defer_usage)
-            parent_defer_usage = parent_defer_usage.parent_defer_usage
-        return ancestors[::-1]
-
 
 class FieldDetails(NamedTuple):
     """A field node and its defer usage."""