Index value from related post type (post object field)

<?php

/**
 * Posts have a "CPU" post object field (ACF)
 * CPUs have a "frequency" and "cores" field
 */
add_filter( 'facetwp_index_row', function( $params, $class ) {
	$name = $params['facet_name'];
	$cpu_id = (int) $params['facet_value'];

    if ( 'cpu_frequency' == $name ) {
		$params['facet_value'] = get_field( 'frequency', $cpu_id );
		$params['facet_display_value'] = get_field( 'frequency', $cpu_id );
	}
	elseif ( 'cpu_cores' == $name ) {
		$params['facet_value'] = get_field( 'cores', $cpu_id );
		$params['facet_display_value'] = get_field( 'cores', $cpu_id );
	}

    return $params;
}, 10, 2 );