Enable WAL journal mode by default for SQLite database

I've just tried brand new Drupal 8 beta1, and for sake for interest, installed it using SQLite database in Kubuntu 14.04 amd64 laptop.

Installation took.. quite a bit. During installation I've noticed that .ht.sqlite has "-joural" file nearby which is created/deleted, so it's rollback journal with journal_mode=DELETE (the default).

I've made small change in core/lib/Drupal/Core/Database/Driver/sqlite/Connection.php, to force WAL journal mode:

--- Connection.php      2014-10-01 12:54:04.175647920 +0300
*************** class Connection extends DatabaseConnect
*** 127,132 ****
--- 127,133 ----
      $pdo->sqliteCreateFunction('rand', array(__CLASS__, 'sqlFunctionRand'));
      $pdo->sqliteCreateFunction('regexp', array(__CLASS__, 'sqlFunctionRegexp'));
  
+     $connection_options['init_commands'] = array('wal' => 'PRAGMA journal_mode=wal');
      // Execute sqlite init_commands.
      if (isset($connection_options['init_commands'])) {
        $pdo->exec(implode('; ', $connection_options['init_commands']));

Now installation is measurably faster.

Using unmodified Drupal source, time of core Drupal modules installation (since "Save and continue" in Database configuration page and until 100% of module installation is reached and loading indicator for next page in browser tab appears) is:
~6m:55s

Using journal_mode=wal:
~2m:46s

I can hear how sparse my laptop HDD drive rattling is in WAL mode, compared to non-stop noise in default journal mode.

It would be nice if upon new installation, if current available PHP SQLite extension supports WAL (since version 3.7.0), that settings.php would be generated in a way that journal_mode=wal would be enabled upon connection.

Possibly, there could be opt-out "Use WAL journal mode" checkbox in "Advanced" fieldset in Drupal installation database settings page, or a select box of all available journal modes, if that felt to be necessary (though more advance/exotic settings/PRAGMAs could be provided in settings.php manually after all).

I do not know if there are some significant drawbacks using this mode in PHP, Drupal, or for web app as whole, please comment if any.

The advantages of Write-Ahead Logging (WAL)

1. WAL is significantly faster in most scenarios.
2. WAL provides more concurrency as readers do not block writers and a writer does not block readers. Reading and writing can proceed concurrently.
3. Disk I/O operations tends to be more sequential using WAL.
4. WAL uses many fewer fsync() operations and is thus less vulnerable to problems on systems where the fsync() system call is broken.