Motivate update hooks with comment

Author: simolus3

Sources/PowerSyncGRDB/Connections/GRDBConnectionPool.swift

@@ -50,8 +50,16 @@ actor GRDBConnectionPool: SQLiteConnectionPoolProtocol {
     func write<T: Sendable>(
         onConnection: @Sendable @escaping (SQLiteConnectionLease) throws -> T
     ) async throws -> T {
-        // Don't start an explicit transaction, we do this internally
+        // Don't start an explicit transaction, we do this internally.
         let (result, updates) = try await pool.writeWithoutTransaction { database in
+            // This installs a temporary update hook, which breaks if GRDB had its own. Currently, we rely on
+            // GRDB only installing update hooks for statements that need it (see https://github.com/groue/GRDB.swift/blob/36e30a6f1ef10e4194f6af0cff90888526f0c115/GRDB/Core/TransactionObserver.swift#L266-L275),
+            // note that `statementObservations` is set in `statementWillExecute` and cleared after a statement
+            // has completed or failed.
+            // So since we have exclusive access to the write connection here, no GRDB-active statement can run and we
+            // can safely install our own hooks.
+            // In the future, we would like to use high-level GRDB APIs for this instead. However, we're blocked
+            // by https://github.com/groue/GRDB.swift/issues/1863 on that.
             try collectWrites(db: database.sqliteConnection!) {
                 try onConnection(GRDBConnectionLease(database: database))
             }