[wp-trac] [WordPress Trac] #16558: switch_to_blog does not properly update global $wpdb

[WordPress Trac]

#16558: switch_to_blog does not properly update global $wpdb
--------------------------+-----------------------------
 Reporter:  divinegod     |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  General       |    Version:  3.0.4
 Severity:  normal        |   Keywords:
--------------------------+-----------------------------
 when using switch_to_blog in a plugin the global $wpdb is not properly
 updated. The $wpdb->posts member is not prefixed correctly causing other
 functions to misbehave.

 To make it behave I had to use $wpdb->set_prefix() passing in the result
 of $wpdb->get_blog_prefix($blog_id), but this sets $wpdb->base_prefix to a
 new value (instead of "wp_". Then subsequent calls to switch_to_blog and
 fixing the $wpdb->posts again, introduces yet another problem: "wp_2_3_"
 as prefix.
 My workaround to this ended up being:

 $wpdb->set_prefix($wpdb->set_prefix($wpdb->get_blog_prefix($blog_id)),
 false);

 I use this in a plugin that iterates over every blog in a network setup,
 getting posts, comments, etc. and caching them in a separate DB.

 sort-of-pseudo code:

 {{{
 function do_stuff() {
   global $wpdb;
   $blogids = $wpdb->get_col($wpdb->prepare("SELECT blog_id FROM
 $wpdb->blogs"));
   foreach ($blogids as $blog_id) {
     switch_to_blog($blog_id);
     stuff($blog_id);
   }
 }
 function stuff($blogid) {
   global $wpdb;
   // $wpdb->posts == "wp_posts"
   $wpdb->set_prefix($wpdb->set_prefix($wpdb->get_blog_prefix($blog_id)),
 false);
   // $wpdb->posts == "wp_$blogid_posts" if $blogid != 1 or 0
 }
 }}}

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Ticket URL: <http://core.trac.wordpress.org/ticket/16558>
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