mihai2k on "wp_posts custom mysql column name"

and here is the solution ..
adding the following in the theme's functions.php

add_filter( 'wp_insert_post_data', 'wp_insert_post_data_filter',1, 2 );

function wp_insert_post_data_filter( $data, $postarr ) {
@    $data['test_col'] = $postarr['custom_data'];
return $data;
}

.. where 'test_col' is the column name from wp_posts
i have put the @ in front of lines because I use it to post via XMLRPC and i was getting some errors while i was not submitting all the values for all variables.

i hope this thing is useful for others