Add boost to exact matches in custom fields

custom_field_boost.php

<?php

add_filter( 'relevanssi_results', 'rlv_exact_boost' );
function rlv_exact_boost( $results ) {
	$query = strtolower( get_search_query() );
	foreach ( $results as $post_id => $weight ) {
    $custom_fields = get_post_meta( $post_id );
    foreach ( $custom_fields as $field => $values ) {
      if ( in_array( $field, array( 'custom_field_1', 'custom_field_2', 'custom_field_3' ), true ) ) {
        $values = implode( ' ', $values );
        if ( stristr( $values, $query ) !== false ) {
          $results[ $post_id ] = $weight * 1000;
        }
      }
    }
  }
  return $results;
}