好的，作为参考，我最终实际使用了switch_to_blog() 和restore_current_blog(). 我没有找到任何用于查询多个表的引用（除了编写自己的表JOIN-语句）执行操作的源代码时pre_get_posts.

有人给了斯基普很多建议restore_current_blog() 为了节省CPU周期，但当我检查源代码时，我发现这会导致巨大的内存问题，因为restore_current_blog() 所做的是将最新插入的对象弹出到全局数组中，并且该数组将随着每个switch_to_blog() 那一个做不到restore_current_blog() 在…上

请随时查看源代码，并查看@user42826对此的回答，网址为https://wordpress.stackexchange.com/a/123516/14820.

对于那些感兴趣的人来说，我最终得到了站点列表和结果的瞬态，以节省CPU周期和DB性能。我只需要更新过时的数据（15分钟或更长时间）。仅包含以下相关功能位：

$site_transient = get_site_transient( \'multisite_site_list\');
if ($site_transient == false || LL_USE_TRANSIENTS == false) {
    $using_site_transient = false;

    // no cache available
    global $wpdb;

    // TODO: get prefix for wp tables
    $site_list = $wpdb->get_results($wpdb->prepare(\'SELECT * FROM nw_blogs WHERE public = %d AND deleted = %d ORDER BY blog_id\', 1, 0));

    // set transient
    set_site_transient(\'multisite_site_list\', $site_list, LL_TRANSIENT_EXPIRES);

} else {
    //log_msg("SITELIST - Transient found, using cached query..");
    $site_list = $site_transient;
    $using_site_transient = true;
}

//log_msg("$id - get_posts_from_network | tags: " . implode(",", $tags) . " | tag_slug__and: $lang_full");

$start = microtime(true);

// get blogpost transient, if existing
$post_transient = get_site_transient( \'limelight_recent_posts_\' . $hash);

// if not, do query and save result as a transient
if ($post_transient == false || LL_USE_TRANSIENTS == false) {
    $using_post_transient = false;
    $blogposts = array();

    foreach ($site_list as $site) {
        switch_to_blog($site->blog_id);
        $posts = get_posts(array(
            \'post_status\' => \'publish\',
            \'orderby\' => \'date\',
            \'order\' => \'desc\',
            \'tag\' => implode(",", $tags),
            \'tag_slug__and\' => array($lang_full)
        ));

        //log_msg("$id - get_posts_form_network | at site: $site->blog_id");

        foreach ($posts as $post) {

            //log_msg("$id - get_posts_form_network | at site: $site->blog_id | got post!");

            $post->human_post_date = human_time_diff(get_post_time(\'U\', false, $post->ID), current_time(\'timestamp\')) . \' \' . __(\'ago\', \'limelight\');

            if (isset($tagline_metabox)) {
                $meta = get_post_meta($post->ID, $tagline_metabox->get_the_id(), TRUE);
                $post->tagline = $meta[\'tagline_text\'];
            }

            if (!isset($post->tagline) || $post->tagline == \'\')
                $post->tagline = substr($post->post_title, 0, 20) . \'..\';

            $post->post_date_timestamp = strtotime($post->post_date);           

            //$post->blog_id = $site->blog_id;
            $post->blog_name = get_bloginfo(\'name\');
            $post->blog_url = get_bloginfo(\'wpurl\');
            $post->permalink = get_permalink($post->ID);
            $post->author_name = get_userdata($post->post_author)->display_name;
            //$data = get_userdata($post->post_author);

            $blogposts[] = $post;
        }
        restore_current_blog();
    }

    // sort blogposts by post_date_timestamp, descending
    array_sort_by_obj($blogposts, \'post_date_timestamp\', SORT_DESC);

    // pick five latest posts
    if (sizeof($blogposts) > 5) {
        $posts = array();
        for ($i = 0; $i <= 4; $i++) {
            $posts[$i] = $blogposts[$i];
        }
        $blogposts = $posts;
    }

    // set transient
    if (LL_USE_TRANSIENTS)
        set_site_transient(\'limelight_recent_posts_\' . $hash, $blogposts, LL_TRANSIENT_EXPIRES);