facetwp index only direct children of a parent term

custom-hooks.php

<?php
/**
 ** filter on facetwp_index_row to index only direct children of a parent term
 ** this is for use with Parent term setting which by default indexes child terms, and grand child terms, etc
 ** If you want to have the index include posts of child/grandchild, etc of terms, you need to set Hierarchical to yes
 **/

add_filter( 'facetwp_index_row', function( $params, $class ) {
	if ( in_array( $params['facet_name'], array( 'my_facet', 'my_other_facet' ) ) ) { // create an array of facet names to check against
	    $parent = $class->facet['parent_term']; // this gives the parent term from the facet's settings
	    if ( $parent != $params['parent_id'] ) { // $params['parent_id'] is the parent id of the term being indexed
	        $params['facet_value'] = ''; // skip indexing
        }
	}
	return $params;
}, 10, 2 );