Optimize queries: add indexes and help older query planners.

src/codehelp/migrations/20240716--codehelp--add-indexes.sql

@@ -0,0 +1,17 @@
+-- SPDX-FileCopyrightText: 2024 Mark Liffiton <[email protected]>
+--
+-- SPDX-License-Identifier: AGPL-3.0-only
+
+BEGIN;
+
+DROP INDEX IF EXISTS queries_by_user;
+CREATE INDEX queries_by_user ON queries(user_id);
+DROP INDEX IF EXISTS queries_by_role;
+CREATE INDEX queries_by_role ON queries(role_id);
+
+DROP INDEX IF EXISTS tutor_chats_by_user;
+CREATE INDEX tutor_chats_by_user ON tutor_chats(user_id);
+DROP INDEX IF EXISTS tutor_chats_by_role;
+CREATE INDEX tutor_chats_by_role ON tutor_chats(role_id);
+
+COMMIT;

src/codehelp/schema.sql

@@ -22,6 +22,10 @@ CREATE TABLE queries (
     FOREIGN KEY(user_id) REFERENCES users(id),
     FOREIGN KEY(role_id) REFERENCES roles(id)
 );
+DROP INDEX IF EXISTS queries_by_user;
+CREATE INDEX queries_by_user ON queries(user_id);
+DROP INDEX IF EXISTS queries_by_role;
+CREATE INDEX queries_by_role ON queries(role_id);
 
 DROP TABLE IF EXISTS tutor_chats;
 CREATE TABLE tutor_chats (
@@ -34,3 +38,7 @@ CREATE TABLE tutor_chats (
     FOREIGN KEY(user_id) REFERENCES users(id),
     FOREIGN KEY(role_id) REFERENCES roles(id)
 );
+DROP INDEX IF EXISTS tutor_chats_by_user;
+CREATE INDEX tutor_chats_by_user ON tutor_chats(user_id);
+DROP INDEX IF EXISTS tutor_chats_by_role;
+CREATE INDEX tutor_chats_by_role ON tutor_chats(role_id);

src/gened/instructor.py

@@ -25,7 +25,7 @@
 def get_queries(class_id: int, user: int | None = None) -> list[Row]:
     db = get_db()
 
-    where_clause = "WHERE roles.class_id=?"
+    where_clause = "WHERE UNLIKELY(roles.class_id=?)"  # UNLIKELY() to help query planner in older sqlite versions
     params = [class_id]
 
     if user is not None: