First : Great work.
Unfortunately some preg_match break compatibility with simplefield plugin ( here)
The issue is here :
$pattern = '/[0-9a-zA-Z_]+ID/'; $sql = preg_replace($pattern, '"$0"', $sql);
While the pg4wp plugin try to handle some particular case on line 431 of the driver_pgsql.php file it escape the value instead of leaving it as it is.
Well, I just found out ... So I will post the solution later today :)
In order to test, just add some meta to a post with the value
You'll see you can add it but you can not delete it !
Great job anyway !