diff --git a/core/lib/Drupal/Core/Database/Driver/pgsql/Install/Tasks.php b/core/lib/Drupal/Core/Database/Driver/pgsql/Install/Tasks.php
index a41cba5..1d62b39 100644
--- a/core/lib/Drupal/Core/Database/Driver/pgsql/Install/Tasks.php
+++ b/core/lib/Drupal/Core/Database/Driver/pgsql/Install/Tasks.php
@@ -192,7 +192,8 @@ function initializeDatabase() {
     // like we do with table names. This is so that we don't double up if more
     // than one instance of Drupal is running on a single database. We therefore
     // avoid trying to create them again in that case.
-
+    // At the same time checking for the existence of the function fixes
+    // concurrency issues, when both try to update at the same time.
     try {
       // Don't use {} around pg_proc table.
       if (!db_query("SELECT COUNT(*) FROM pg_proc WHERE proname = 'rand'")->fetchField()) {