Source

File: wp-includes/pluggable.php

function cache_users( $user_ids ) {
		global $wpdb;

		$clean = _get_non_cached_ids( $user_ids, 'users' );

		if ( empty( $clean ) ) {
			return;
		}

		$list = implode( ',', $clean );

		$users = $wpdb->get_results( "SELECT * FROM $wpdb->users WHERE ID IN ($list)" );

		$ids = array();
		foreach ( $users as $user ) {
			update_user_caches( $user );
			$ids[] = $user->ID;
		}
		update_meta_cache( 'user', $ids );
	}