When inserting data into a bytea column from a binary file (e.g. a PNG image - using the "Insert" form, that creates a file input for such column), I get the following error:
ERROR: invalid byte sequence for encoding "UTF8": 0x89
I get this error too using latest code from github (2015-03-03).
Here's a work around:
In the process_input() function (in functions.inc.php) you'll see where it handles bytea and other binary types. Instead of
$file = base64_encode($file);
return "decode('$file', 'base64')";
This is postgresql specific of course. It wouldn't be too hard to make this work around proper by making q() take an optional "is_binary" parameter. Each driver could handle binary quoting in it's own way.
Adminer is a great tool but, in my opinion, it handles binary data poorly. Binary data should be handled with prepared statements, not quoted like a string. The PHP docs on PDO::quote() say as much.