core: index group members by role for moderator lookup

The moderator lookup of a large group read every member row of the
group to filter on role, holding the database connection while it ran:
178 ms on average and 4.8 s at most on one device. A new index on
(user_id, member_role, group_id) serves the role-filtered member
queries. The (user_id, group_id) index stays, so the other queries keep
their plans and the order of their results.

simplex-chat.cabal

@@ -172,6 +172,7 @@ library
           Simplex.Chat.Store.Postgres.Migrations.M20261010_invite_member_via_group
           Simplex.Chat.Store.Postgres.Migrations.M20261012_delivery_job_notification
           Simplex.Chat.Store.Postgres.Migrations.M20261016_badge_store_receipts
+          Simplex.Chat.Store.Postgres.Migrations.M20261018_member_role_index
   else
       exposed-modules:
           Simplex.Chat.Archive
@@ -353,6 +354,7 @@ library
           Simplex.Chat.Store.SQLite.Migrations.M20261010_invite_member_via_group
           Simplex.Chat.Store.SQLite.Migrations.M20261012_delivery_job_notification
           Simplex.Chat.Store.SQLite.Migrations.M20261016_badge_store_receipts
+          Simplex.Chat.Store.SQLite.Migrations.M20261018_member_role_index
   other-modules:
       Paths_simplex_chat
   hs-source-dirs:

src/Simplex/Chat/Store/Postgres/Migrations.hs

@@ -57,6 +57,7 @@ import Simplex.Chat.Store.Postgres.Migrations.M20260925_badge_bindings
 import Simplex.Chat.Store.Postgres.Migrations.M20261010_invite_member_via_group
 import Simplex.Chat.Store.Postgres.Migrations.M20261012_delivery_job_notification
 import Simplex.Chat.Store.Postgres.Migrations.M20261016_badge_store_receipts
+import Simplex.Chat.Store.Postgres.Migrations.M20261018_member_role_index
 import Simplex.Messaging.Agent.Store.Shared (Migration (..))
 
 schemaMigrations :: [(String, Text, Maybe Text)]
@@ -113,7 +114,8 @@ schemaMigrations =
     ("20260925_badge_bindings", m20260925_badge_bindings, Just down_m20260925_badge_bindings),
     ("20261010_invite_member_via_group", m20261010_invite_member_via_group, Just down_m20261010_invite_member_via_group),
     ("20261012_delivery_job_notification", m20261012_delivery_job_notification, Just down_m20261012_delivery_job_notification),
-    ("20261016_badge_store_receipts", m20261016_badge_store_receipts, Just down_m20261016_badge_store_receipts)
+    ("20261016_badge_store_receipts", m20261016_badge_store_receipts, Just down_m20261016_badge_store_receipts),
+    ("20261018_member_role_index", m20261018_member_role_index, Just down_m20261018_member_role_index)
   ]
 
 -- | The list of migrations in ascending order by date

src/Simplex/Chat/Store/Postgres/Migrations/M20261018_member_role_index.hs

@@ -0,0 +1,19 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes #-}
+
+module Simplex.Chat.Store.Postgres.Migrations.M20261018_member_role_index where
+
+import Data.Text (Text)
+import Text.RawString.QQ (r)
+
+m20261018_member_role_index :: Text
+m20261018_member_role_index =
+  [r|
+CREATE INDEX idx_group_members_user_id_member_role ON group_members(user_id, member_role, group_id);
+|]
+
+down_m20261018_member_role_index :: Text
+down_m20261018_member_role_index =
+  [r|
+DROP INDEX idx_group_members_user_id_member_role;
+|]

src/Simplex/Chat/Store/Postgres/Migrations/chat_schema.sql

@@ -2781,6 +2781,10 @@ CREATE INDEX idx_group_members_user_id_local_display_name ON test_chat_schema.gr
 
 
 
+CREATE INDEX idx_group_members_user_id_member_role ON test_chat_schema.group_members USING btree (user_id, member_role, group_id);
+
+
+
 CREATE INDEX idx_group_profiles_user_id ON test_chat_schema.group_profiles USING btree (user_id);
 
 

src/Simplex/Chat/Store/SQLite/Migrations.hs

@@ -180,6 +180,7 @@ import Simplex.Chat.Store.SQLite.Migrations.M20260925_badge_bindings
 import Simplex.Chat.Store.SQLite.Migrations.M20261010_invite_member_via_group
 import Simplex.Chat.Store.SQLite.Migrations.M20261012_delivery_job_notification
 import Simplex.Chat.Store.SQLite.Migrations.M20261016_badge_store_receipts
+import Simplex.Chat.Store.SQLite.Migrations.M20261018_member_role_index
 import Simplex.Messaging.Agent.Store.Shared (Migration (..))
 
 schemaMigrations :: [(String, Query, Maybe Query)]
@@ -359,7 +360,8 @@ schemaMigrations =
     ("20260925_badge_bindings", m20260925_badge_bindings, Just down_m20260925_badge_bindings),
     ("20261010_invite_member_via_group", m20261010_invite_member_via_group, Just down_m20261010_invite_member_via_group),
     ("20261012_delivery_job_notification", m20261012_delivery_job_notification, Just down_m20261012_delivery_job_notification),
-    ("20261016_badge_store_receipts", m20261016_badge_store_receipts, Just down_m20261016_badge_store_receipts)
+    ("20261016_badge_store_receipts", m20261016_badge_store_receipts, Just down_m20261016_badge_store_receipts),
+    ("20261018_member_role_index", m20261018_member_role_index, Just down_m20261018_member_role_index)
   ]
 
 -- | The list of migrations in ascending order by date

src/Simplex/Chat/Store/SQLite/Migrations/M20261018_member_role_index.hs

@@ -0,0 +1,18 @@
+{-# LANGUAGE QuasiQuotes #-}
+
+module Simplex.Chat.Store.SQLite.Migrations.M20261018_member_role_index where
+
+import Database.SQLite.Simple (Query)
+import Database.SQLite.Simple.QQ (sql)
+
+m20261018_member_role_index :: Query
+m20261018_member_role_index =
+  [sql|
+CREATE INDEX idx_group_members_user_id_member_role ON group_members(user_id, member_role, group_id);
+|]
+
+down_m20261018_member_role_index :: Query
+down_m20261018_member_role_index =
+  [sql|
+DROP INDEX idx_group_members_user_id_member_role;
+|]

src/Simplex/Chat/Store/SQLite/Migrations/chat_query_plans.txt

@@ -6242,7 +6242,7 @@ Query:
     LEFT JOIN group_member_badge_proofs bp ON bp.group_member_id = m.group_member_id
    WHERE m.user_id = ? AND m.group_id = ? AND (m.contact_id IS NULL OR m.contact_id != ?) AND m.member_role = ?
 Plan:
-SEARCH m USING INDEX idx_group_members_group_id (user_id=? AND group_id=?)
+SEARCH m USING INDEX idx_group_members_user_id_member_role (user_id=? AND member_role=? AND group_id=?)
 SEARCH p USING INTEGER PRIMARY KEY (rowid=?)
 SEARCH c USING INDEX idx_connections_group_member_id (group_member_id=?) LEFT-JOIN
 SEARCH bp USING INTEGER PRIMARY KEY (rowid=?) LEFT-JOIN
@@ -6265,7 +6265,7 @@ Query:
     LEFT JOIN group_member_badge_proofs bp ON bp.group_member_id = m.group_member_id
    WHERE m.user_id = ? AND m.group_id = ? AND (m.contact_id IS NULL OR m.contact_id != ?) AND m.member_role IN (?,?)
 Plan:
-SEARCH m USING INDEX idx_group_members_group_id (user_id=? AND group_id=?)
+SEARCH m USING INDEX idx_group_members_user_id_member_role (user_id=? AND member_role=? AND group_id=?)
 SEARCH p USING INTEGER PRIMARY KEY (rowid=?)
 SEARCH c USING INDEX idx_connections_group_member_id (group_member_id=?) LEFT-JOIN
 SEARCH bp USING INTEGER PRIMARY KEY (rowid=?) LEFT-JOIN
@@ -6288,7 +6288,7 @@ Query:
     LEFT JOIN group_member_badge_proofs bp ON bp.group_member_id = m.group_member_id
    WHERE m.user_id = ? AND m.group_id = ? AND (m.contact_id IS NULL OR m.contact_id != ?) AND m.member_role IN (?,?,?)
 Plan:
-SEARCH m USING INDEX idx_group_members_group_id (user_id=? AND group_id=?)
+SEARCH m USING INDEX idx_group_members_user_id_member_role (user_id=? AND member_role=? AND group_id=?)
 SEARCH p USING INTEGER PRIMARY KEY (rowid=?)
 SEARCH c USING INDEX idx_connections_group_member_id (group_member_id=?) LEFT-JOIN
 SEARCH bp USING INTEGER PRIMARY KEY (rowid=?) LEFT-JOIN
@@ -6311,7 +6311,7 @@ Query:
     LEFT JOIN group_member_badge_proofs bp ON bp.group_member_id = m.group_member_id
    WHERE m.user_id = ? AND m.group_id = ? AND m.contact_id IS DISTINCT FROM ? AND m.member_role = ?
 Plan:
-SEARCH m USING INDEX idx_group_members_group_id (user_id=? AND group_id=?)
+SEARCH m USING INDEX idx_group_members_user_id_member_role (user_id=? AND member_role=? AND group_id=?)
 SEARCH p USING INTEGER PRIMARY KEY (rowid=?)
 SEARCH c USING INDEX idx_connections_group_member_id (group_member_id=?) LEFT-JOIN
 SEARCH bp USING INTEGER PRIMARY KEY (rowid=?) LEFT-JOIN

src/Simplex/Chat/Store/SQLite/Migrations/chat_schema.sql

@@ -1584,6 +1584,11 @@ CREATE INDEX idx_badge_store_receipts_user ON badge_store_receipts(user_id);
 CREATE UNIQUE INDEX idx_badge_purchases_store_receipt ON badge_purchases(
   badge_store_receipt_id
 );
+CREATE INDEX idx_group_members_user_id_member_role ON group_members(
+  user_id,
+  member_role,
+  group_id
+);
 CREATE TRIGGER on_group_members_insert_update_summary
 AFTER INSERT ON group_members
 FOR EACH ROW