WordPress at a glance
action is not described

posts_selection action-hook . WP 2.3.0

Fires to announce the query's current selection parameters.

For use by caching plugins.

Usage

add_action( 'posts_selection', 'action_function_name_1550' );
function action_function_name_1550( $selection ){
	// action...
}
$selection(string)
The assembled selection query.

Where the hook is called

WP_Query::get_posts()
wp-includes/class-wp-query.php 2602
do_action( 'posts_selection', $where . $groupby . $orderby . $limits . $join );

Where the hook is used (in WP core)

Does not used.