internal/db: optimize session list indexes

internal/db/schema/migrations/oss/postgres/28/01_session_create_time_idx.up.sql

@@ -4,6 +4,7 @@
 begin;
 -- Session list queries always use an order by on create_time.
 -- This index can aide in performing this order by.
+-- Dropped in 81/05_session_base_table_updates.up.sql.
 create index
   session_create_time
 on

internal/db/schema/migrations/oss/postgres/50/01_session_list_index.up.sql

@@ -9,6 +9,7 @@ begin;
   -- it will include where clauses that:
   --  * include a project_id paired with a user_id
   --  * and where termination_reason is null
+  -- Dropped in 81/05_session_base_table_updates.up.sql.
   create index session_list_pix on session (project_id, user_id, termination_reason) where termination_reason is null;
   analyze session;
 end;

internal/db/schema/migrations/oss/postgres/81/05_session_base_table_updates.up.sql

@@ -3,11 +3,33 @@
 
 begin;
 
-  -- Add new indexes for the create time and update time queries.
-  create index session_create_time_public_id_idx
-      on session (create_time desc, public_id desc);
-  create index session_update_time_public_id_idx
-      on session (update_time desc, public_id desc);
+  -- Drop old list indexes that interfere with the new list requests.
+  drop index session_create_time, session_list_pix;
+
+  -- Add new indexes for the list queries. These indexes have been
+  -- carefully tested to cover the different expected queries.
+  create index session_project_id_create_time_list_idx
+            on session (project_id,
+                        create_time desc,
+                        public_id   desc,
+                        termination_reason);
+  create index session_project_id_update_time_list_idx
+            on session (project_id,
+                        update_time desc,
+                        public_id   desc,    
+                        termination_reason);
+  create index session_user_id_project_id_create_time_list_idx
+            on session (user_id,
+                        project_id,
+                        create_time desc,
+                        public_id   desc,
+                        termination_reason);
+  create index session_user_id_project_id_update_time_list_idx
+            on session (user_id,
+                        project_id,         
+                        update_time desc,
+                        public_id   desc,
+                        termination_reason);
 
   analyze session;
 

internal/db/sqltest/tests/pagination/session.sql

@@ -2,11 +2,13 @@
 -- SPDX-License-Identifier: BUSL-1.1
 
 begin;
-  select plan(2);
+  select plan(4);
 
-  select has_index('session', 'session_create_time_public_id_idx', array['create_time', 'public_id']);
-  select has_index('session', 'session_update_time_public_id_idx', array['update_time', 'public_id']);
+  select has_index('session', 'session_project_id_create_time_list_idx', array['project_id', 'create_time', 'public_id', 'termination_reason']);
+  select has_index('session', 'session_project_id_update_time_list_idx', array['project_id', 'update_time', 'public_id', 'termination_reason']);
+  select has_index('session', 'session_user_id_project_id_create_time_list_idx', array['user_id', 'project_id', 'create_time', 'public_id', 'termination_reason']);
+  select has_index('session', 'session_user_id_project_id_update_time_list_idx', array['user_id', 'project_id', 'update_time', 'public_id', 'termination_reason']);
 
   select * from finish();
 
-rollback;
+rollback;