Authors mapping and caching bug

Resolved Inderpreet Singh
(@inderpreet99)

11 years, 10 months ago
Hi,

Great job on the plugin.

I found a very specific bug relating to object cache plugins. The following line that saves the authors from the user submitted mapping to save_authors():292 does not properly clear the object cache related to each post.

$wpdb->query($wpdb->prepare("UPDATE $wpdb->posts SET post_author = %d WHERE id IN ($post_ids)", $user_id));

Sites with caching plugins, such as W3 Total Cache or Memcached Object Cache, users will see no change. They will continue to see the user that imported the posts as the author until the cache is cleared (for each post or the entire site). To fix this, I propose that we use:
```
foreach( $post_ids as $p ) {
  wp_update_post( array(
    'ID'           => $p,
    'post_author' => $user_id,
  ) );
}
```
This should clear the proper caches. Thanks.

https://ww.wp.xz.cn/plugins/blogger-importer/

Viewing 4 replies - 1 through 4 (of 4 total)

Plugin Author Workshopshed
(@workshopshed)

11 years, 10 months ago

Yes it’s a good idea to avoid the use of prepared queries if something like wp_update_post can be used instead. The difference is that rather than passing one query per author to update the posts it will pass as many queries as there are posts.

Have you looked at how this will perform with a few thousand posts? Let me know if it performs ok and we can swap it in.

I would recommend turning off caching for the duration of importing, in fact I’d recommend turning off as many other plugins and themese as you can.

Plugin Contributor Samuel Wood (Otto)
(@otto42)

ww.wp.xz.cn Admin

11 years, 10 months ago

All forms of caching should be entirely disabled when doing an import of any sort. In fact, I’d go so far as to say that all other plugins should be disabled when performing an import.

The purpose of an import is to get the content into the system, one time. To do this in a sane and fast manner, a fair amount of the normal publishing process is usually bypassed. Caches are disabled, meta queries aren’t run, things like that.

The thing is that inserting a post is usually a rather expensive operation in WordPress, mainly because it isn’t something you do often. Once or twice an hour, tops. When you’re talking about inserting several thousand posts in a few minutes, all that extra work that happens on post creation needs to be skipped. Since importing is generally a one-time operation, and one that usually happens on a new site (migration from an older site is the most common case for needing an importer), then it’s not usually the case where caching plugins already exist and such.

If there was a solid and safe way to force disable all other plugins and all other caching mechanism during an import, I’d add that to the code. But there isn’t. Too many plugins doing too many odd things. So at the moment, my suggestion would be to add “disable all other plugins and caching during the import” to the instructions instead.

Thread Starter Inderpreet Singh
(@inderpreet99)

11 years, 10 months ago

I see that my suggestion to run wp_update_post was a shortsighted, since this can spiral out of control for large sites.

I agree with adding the language as Samuel Wood suggested. This way users can either choose to disable other plugins beforehand, or at least fix the problem by clearing cache afterwards.

Thanks.

Plugin Author Workshopshed
(@workshopshed)

11 years, 10 months ago

I’ve added the following to the readme

= Preparation =

It is strongly recommended that you **disable all other plugins and caching** during the import.

This will ensure that the information transfers across as smoothly as possible and that posts and comments are correctly transferrred.

Viewing 4 replies - 1 through 4 (of 4 total)

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