Enable Relvanssi search plugin to index custom fields

Enable Relvanssi search plugin to index custom fields

<?php
// Use this if you need the Relevanssi advanced search plugin to index content in custom fields.
add_filter('relevanssi_excerpt_content', 'excerpt_function', 10, 3);
function excerpt_function($content, $post, $query) {
	global $wpdb;
	$fields = $wpdb->get_col("SELECT DISTINCT(meta_key) FROM $wpdb->postmeta");

	foreach($fields as $key => $field){
		$field_value = get_post_meta($post->ID, $field, TRUE);
		$content .= ' ' . ( is_array($field_value) ? implode(' ', $field_value) : $field_value );
	}
	return $content;
}
?>