WordPress at a glance
filter is not described

sites_clauses filter-hook . WP 4.6.0

Filters the site query clauses.

Usage

add_filter( 'sites_clauses', 'filter_function_name_847', 10, 2 );
function filter_function_name_847( $pieces, $this ){
	// filter...

	return $pieces;
}
$pieces(array)
A compacted array of site query clauses.
$this(WP_Site_Query)
Current instance of WP_Site_Query (passed by reference).

Where the hook is called

WP_Site_Query::get_site_ids()
wp-includes/class-wp-site-query.php 541
$clauses = apply_filters_ref_array( 'sites_clauses', array( compact( $pieces ), &$this ) );

Where the hook is used (in WP core)

Does not used.