perf: batch fetch flag comparison data

apps/worker/tasks/compute_comparison.py

@@ -135,36 +135,53 @@ def create_or_update_flag_comparisons(
         comparison_proxy: ComparisonProxy,
     ):
         repository_id = comparison.compare_commit.repository.repoid
-        for flag_name in head_report_flags.keys():
-            totals = self.get_flag_comparison_totals(flag_name, comparison_proxy)
-            repositoryflag = (
-                db_session.query(RepositoryFlag)
-                .filter_by(
-                    flag_name=flag_name,
-                    repository_id=repository_id,
-                )
-                .first()
+        flag_names = list(head_report_flags.keys())
+
+        # Batch-fetch all RepositoryFlag records for this repository matching
+        # the flag names in the head report, to avoid one query per flag.
+        existing_repository_flags: dict[str, RepositoryFlag] = {
+            rf.flag_name: rf
+            for rf in db_session.query(RepositoryFlag)
+            .filter(
+                RepositoryFlag.repository_id == repository_id,
+                RepositoryFlag.flag_name.in_(flag_names),
             )
-            if not repositoryflag:
+            .all()
+        }
+
+        # Create any missing RepositoryFlag records up front so we can
+        # build a complete id→flag map before querying CompareFlag.
+        for flag_name in flag_names:
+            if flag_name not in existing_repository_flags:
                 log.warning(
                     "Repository flag not found for flag. Created repository flag.",
                     extra={"repoid": repository_id, "flag_name": flag_name},
                 )
-                repositoryflag = RepositoryFlag(
+                new_flag = RepositoryFlag(
                     repository_id=repository_id,
                     flag_name=flag_name,
                 )
-                db_session.add(repositoryflag)
+                db_session.add(new_flag)
                 db_session.flush()
-
-            flag_comparison_entry = (
-                db_session.query(CompareFlag)
-                .filter_by(
-                    commit_comparison_id=comparison.id,
-                    repositoryflag_id=repositoryflag.id,
-                )
-                .first()
+                existing_repository_flags[flag_name] = new_flag
+
+        # Batch-fetch all CompareFlag records for this comparison whose
+        # repositoryflag_id is among the flags we care about.
+        repositoryflag_ids = [rf.id for rf in existing_repository_flags.values()]
+        existing_flag_comparisons: dict[int, CompareFlag] = {
+            cf.repositoryflag_id: cf
+            for cf in db_session.query(CompareFlag)
+            .filter(
+                CompareFlag.commit_comparison_id == comparison.id,
+                CompareFlag.repositoryflag_id.in_(repositoryflag_ids),
             )
+            .all()
+        }
+
+        for flag_name in flag_names:
+            totals = self.get_flag_comparison_totals(flag_name, comparison_proxy)
+            repositoryflag = existing_repository_flags[flag_name]
+            flag_comparison_entry = existing_flag_comparisons.get(repositoryflag.id)
 
             if not flag_comparison_entry:
                 log.debug(