Use sync API database in `filterSharedUsers` (#2572)

* Add function to the sync API storage package for filtering shared users

* Use the database instead of asking the RS API

* Fix unit tests

* Fix map handling in `filterSharedUsers`

5 files changed, 76 insertions, 1 deletions

diff --git a/syncapi/storage/interface.go b/syncapi/storage/interface.go
index 5a036d88..05542603 100644
--- a/syncapi/storage/interface.go
+++ b/syncapi/storage/interface.go
@@ -27,6 +27,8 @@ import (
 
 type Database interface {
 	Presence
+	SharedUsers
+
 	MaxStreamPositionForPDUs(ctx context.Context) (types.StreamPosition, error)
 	MaxStreamPositionForReceipts(ctx context.Context) (types.StreamPosition, error)
 	MaxStreamPositionForInvites(ctx context.Context) (types.StreamPosition, error)
@@ -165,3 +167,8 @@ type Presence interface {
 	PresenceAfter(ctx context.Context, after types.StreamPosition, filter gomatrixserverlib.EventFilter) (map[string]*types.PresenceInternal, error)
 	MaxStreamPositionForPresence(ctx context.Context) (types.StreamPosition, error)
 }
+
+type SharedUsers interface {
+	// SharedUsers returns a subset of otherUserIDs that share a room with userID.
+	SharedUsers(ctx context.Context, userID string, otherUserIDs []string) ([]string, error)
+}
diff --git a/syncapi/storage/postgres/current_room_state_table.go b/syncapi/storage/postgres/current_room_state_table.go
index 8ee387b3..c4667baf 100644
--- a/syncapi/storage/postgres/current_room_state_table.go
+++ b/syncapi/storage/postgres/current_room_state_table.go
@@ -107,6 +107,11 @@ const selectEventsWithEventIDsSQL = "" +
 	"SELECT event_id, added_at, headered_event_json, 0 AS session_id, false AS exclude_from_sync, '' AS transaction_id" +
 	" FROM syncapi_current_room_state WHERE event_id = ANY($1)"
 
+const selectSharedUsersSQL = "" +
+	"SELECT state_key FROM syncapi_current_room_state WHERE room_id = ANY(" +
+	"	SELECT room_id FROM syncapi_current_room_state WHERE state_key = $1 AND membership='join'" +
+	") AND state_key = ANY($2) AND membership='join';"
+
 type currentRoomStateStatements struct {
 	upsertRoomStateStmt                *sql.Stmt
 	deleteRoomStateByEventIDStmt       *sql.Stmt
@@ -118,6 +123,7 @@ type currentRoomStateStatements struct {
 	selectJoinedUsersInRoomStmt        *sql.Stmt
 	selectEventsWithEventIDsStmt       *sql.Stmt
 	selectStateEventStmt               *sql.Stmt
+	selectSharedUsersStmt              *sql.Stmt
 }
 
 func NewPostgresCurrentRoomStateTable(db *sql.DB) (tables.CurrentRoomState, error) {
@@ -156,6 +162,9 @@ func NewPostgresCurrentRoomStateTable(db *sql.DB) (tables.CurrentRoomState, erro
 	if s.selectStateEventStmt, err = db.Prepare(selectStateEventSQL); err != nil {
 		return nil, err
 	}
+	if s.selectSharedUsersStmt, err = db.Prepare(selectSharedUsersSQL); err != nil {
+		return nil, err
+	}
 	return s, nil
 }
 
@@ -379,3 +388,24 @@ func (s *currentRoomStateStatements) SelectStateEvent(
 	}
 	return &ev, err
 }
+
+func (s *currentRoomStateStatements) SelectSharedUsers(
+	ctx context.Context, txn *sql.Tx, userID string, otherUserIDs []string,
+) ([]string, error) {
+	stmt := sqlutil.TxStmt(txn, s.selectSharedUsersStmt)
+	rows, err := stmt.QueryContext(ctx, userID, otherUserIDs)
+	if err != nil {
+		return nil, err
+	}
+	defer internal.CloseAndLogIfError(ctx, rows, "selectSharedUsersStmt: rows.close() failed")
+
+	var stateKey string
+	result := make([]string, 0, len(otherUserIDs))
+	for rows.Next() {
+		if err := rows.Scan(&stateKey); err != nil {
+			return nil, err
+		}
+		result = append(result, stateKey)
+	}
+	return result, rows.Err()
+}
diff --git a/syncapi/storage/shared/syncserver.go b/syncapi/storage/shared/syncserver.go
index 76114aff..d1c5e2d1 100644
--- a/syncapi/storage/shared/syncserver.go
+++ b/syncapi/storage/shared/syncserver.go
@@ -176,6 +176,10 @@ func (d *Database) AllPeekingDevicesInRooms(ctx context.Context) (map[string][]t
 	return d.Peeks.SelectPeekingDevices(ctx)
 }
 
+func (d *Database) SharedUsers(ctx context.Context, userID string, otherUserIDs []string) ([]string, error) {
+	return d.CurrentRoomState.SelectSharedUsers(ctx, nil, userID, otherUserIDs)
+}
+
 func (d *Database) GetStateEvent(
 	ctx context.Context, roomID, evType, stateKey string,
 ) (*gomatrixserverlib.HeaderedEvent, error) {
diff --git a/syncapi/storage/sqlite3/current_room_state_table.go b/syncapi/storage/sqlite3/current_room_state_table.go
index f0a1c7bb..376c3a3d 100644
--- a/syncapi/storage/sqlite3/current_room_state_table.go
+++ b/syncapi/storage/sqlite3/current_room_state_table.go
@@ -91,6 +91,11 @@ const selectEventsWithEventIDsSQL = "" +
 	"SELECT event_id, added_at, headered_event_json, 0 AS session_id, false AS exclude_from_sync, '' AS transaction_id" +
 	" FROM syncapi_current_room_state WHERE event_id IN ($1)"
 
+const selectSharedUsersSQL = "" +
+	"SELECT state_key FROM syncapi_current_room_state WHERE room_id = ANY(" +
+	"	SELECT room_id FROM syncapi_current_room_state WHERE state_key = $1 AND membership='join'" +
+	") AND state_key IN ($2) AND membership='join';"
+
 type currentRoomStateStatements struct {
 	db                                 *sql.DB
 	streamIDStatements                 *StreamIDStatements
@@ -100,8 +105,9 @@ type currentRoomStateStatements struct {
 	selectRoomIDsWithMembershipStmt    *sql.Stmt
 	selectRoomIDsWithAnyMembershipStmt *sql.Stmt
 	selectJoinedUsersStmt              *sql.Stmt
-	//selectJoinedUsersInRoomStmt        *sql.Stmt - prepared at runtime due to variadic
+	//selectJoinedUsersInRoomStmt      *sql.Stmt - prepared at runtime due to variadic
 	selectStateEventStmt *sql.Stmt
+	//selectSharedUsersSQL             *sql.Stmt - prepared at runtime due to variadic
 }
 
 func NewSqliteCurrentRoomStateTable(db *sql.DB, streamID *StreamIDStatements) (tables.CurrentRoomState, error) {
@@ -396,3 +402,29 @@ func (s *currentRoomStateStatements) SelectStateEvent(
 	}
 	return &ev, err
 }
+
+func (s *currentRoomStateStatements) SelectSharedUsers(
+	ctx context.Context, txn *sql.Tx, userID string, otherUserIDs []string,
+) ([]string, error) {
+	query := strings.Replace(selectSharedUsersSQL, "($2)", sqlutil.QueryVariadicOffset(len(otherUserIDs), 1), 1)
+	stmt, err := s.db.Prepare(query)
+	if err != nil {
+		return nil, fmt.Errorf("SelectSharedUsers s.db.Prepare: %w", err)
+	}
+	defer internal.CloseAndLogIfError(ctx, stmt, "SelectSharedUsers: stmt.close() failed")
+	rows, err := sqlutil.TxStmt(txn, stmt).QueryContext(ctx, userID, otherUserIDs)
+	if err != nil {
+		return nil, err
+	}
+	defer internal.CloseAndLogIfError(ctx, rows, "selectSharedUsersStmt: rows.close() failed")
+
+	var stateKey string
+	result := make([]string, 0, len(otherUserIDs))
+	for rows.Next() {
+		if err := rows.Scan(&stateKey); err != nil {
+			return nil, err
+		}
+		result = append(result, stateKey)
+	}
+	return result, rows.Err()
+}
diff --git a/syncapi/storage/tables/interface.go b/syncapi/storage/tables/interface.go
index ccdebfdb..08568d9a 100644
--- a/syncapi/storage/tables/interface.go
+++ b/syncapi/storage/tables/interface.go
@@ -104,6 +104,8 @@ type CurrentRoomState interface {
 	SelectJoinedUsers(ctx context.Context) (map[string][]string, error)
 	// SelectJoinedUsersInRoom returns a map of room ID to a list of joined user IDs for a given room.
 	SelectJoinedUsersInRoom(ctx context.Context, roomIDs []string) (map[string][]string, error)
+	// SelectSharedUsers returns a subset of otherUserIDs that share a room with userID.
+	SelectSharedUsers(ctx context.Context, txn *sql.Tx, userID string, otherUserIDs []string) ([]string, error)
 }
 
 // BackwardsExtremities keeps track of backwards extremities for a room.