function _wp_batch_split_terms() {
  global $wpdb;

  $lock_name = 'term_split.lock';

  // Try to lock.
  $lock_result = $wpdb->query( $wpdb->prepare( "INSERT IGNORE INTO `$wpdb->options` ( `option_name`, `option_value`, `autoload` ) VALUES (%s, %s, 'no') /* LOCK */", $lock_name, time() ) );

  if ( ! $lock_result ) {
    $lock_result = get_option( $lock_name );

    // Bail if we were unable to create a lock, or if the existing lock is still valid.
    if ( ! $lock_result || ( $lock_result > ( time() - HOUR_IN_SECONDS ) ) ) {
      wp_schedule_single_event( time() + ( 5 * MINUTE_IN_SECONDS ), 'wp_split_shared_term_batch' );
      return;
    }
  }

  // Update the lock, as by this point we've definitely got a lock, just need to fire the actions.
  update_option( $lock_name, time() );

  // Get a list of shared terms (those with more than one associated row in term_taxonomy).
  $shared_terms = $wpdb->get_results(
    "SELECT tt.term_id, t.*, count(*) as term_tt_count FROM {$wpdb->term_taxonomy} tt
		 LEFT JOIN {$wpdb->terms} t ON t.term_id = tt.term_id
		 GROUP BY t.term_id
		 HAVING term_tt_count > 1
		 LIMIT 10"
  );

  // No more terms, we're done here.
  if ( ! $shared_terms ) {
    update_option( 'finished_splitting_shared_terms', true );
    delete_option( $lock_name );
    return;
  }

  // Shared terms found? We'll need to run this script again.
  wp_schedule_single_event( time() + ( 2 * MINUTE_IN_SECONDS ), 'wp_split_shared_term_batch' );

  // Rekey shared term array for faster lookups.
  $_shared_terms = array();
  foreach ( $shared_terms as $shared_term ) {
    $term_id                   = (int) $shared_term->term_id;
    $_shared_terms[ $term_id ] = $shared_term;
  }
  $shared_terms = $_shared_terms;

  // Get term taxonomy data for all shared terms.
  $shared_term_ids = implode( ',', array_keys( $shared_terms ) );
  $shared_tts      = $wpdb->get_results( "SELECT * FROM {$wpdb->term_taxonomy} WHERE `term_id` IN ({$shared_term_ids})" );

  // Split term data recording is slow, so we do it just once, outside the loop.
  $split_term_data    = get_option( '_split_terms', array() );
  $skipped_first_term = array();
  $taxonomies         = array();
  foreach ( $shared_tts as $shared_tt ) {
    $term_id = (int) $shared_tt->term_id;

    // Don't split the first tt belonging to a given term_id.
    if ( ! isset( $skipped_first_term[ $term_id ] ) ) {
      $skipped_first_term[ $term_id ] = 1;
      continue;
    }

    if ( ! isset( $split_term_data[ $term_id ] ) ) {
      $split_term_data[ $term_id ] = array();
    }

    // Keep track of taxonomies whose hierarchies need flushing.
    if ( ! isset( $taxonomies[ $shared_tt->taxonomy ] ) ) {
      $taxonomies[ $shared_tt->taxonomy ] = 1;
    }

    // Split the term.
    $split_term_data[ $term_id ][ $shared_tt->taxonomy ] = _split_shared_term( $shared_terms[ $term_id ], $shared_tt, false );
  }

  // Rebuild the cached hierarchy for each affected taxonomy.
  foreach ( array_keys( $taxonomies ) as $tax ) {
    delete_option( "{$tax}_children" );
    _get_term_hierarchy( $tax );
  }

  update_option( '_split_terms', $split_term_data );

  delete_option( $lock_name );
}