Programming Note

I am using WordPress 2.7. WordPress has an annoying function: revisions. If you use WordPress 2.6 or above, there may be lots of unuseful revisions in your database. Normally, a post have 5 or more revisions. They make the database larger and larger. Since there are lots of rubbish, the efficiency may become very slow.

Many people want to disable the “revision” function, but WordPress doesn’t provide any option to do it. I see there are some plugins that can turn off the revision function. However, they doesn’t work well. For example, although you have activated the plugin, when you edit a post, autosave can still produce “revisions”. To solve this problem, you can use “disable autosave” plugin to turn off autosave. However, I think autosave is a good feature. I want to find a way to solve the problem: disable revisions but not for autosave. Fortunately, WordPress is an open-source application, so I can know the mechanism of it.

By checking the source code, I found that there can’t be any plugin to satisfy my requirement. So I have to hack WordPress. At last, I found a simple way, only 2 lines need to be changed! Let’s have a look.

Open wp-includes\default-filters.php and find the line

add_action( 'pre_post_update', 'wp_save_post_revision' );

It means the function ‘wp_save_post_revision’ is hooked ‘pre_post’update’. i.e. when you update a post, WordPress will call ‘wp_save_post_revision’ function and it will save a revision for the current post. Of cource, the revision isn’t useful. So I need to remove or comment it:

// add_action( 'pre_post_update', 'wp_save_post_revision' );

Now when you update a post, it doesn’t produce revisions any more. However, when you edit a published post in WordPress, the autosave function can still generate a revision draft. It is not what I want, so I must to solve the problem.

Open wp-admin\includes\post.php and found the function wp_create_post_autosave (near line 1030). The last 2 lines should be

// Otherwise create the new autosave as a special post revision
return _wp_put_post_revision( $_POST, true );

Through the comment I see it create a new revision from the $_POST array. I changed it to “return edit_post();” and tested in diffent conditions. I found it works well. Now the function wp_create_post_autosave looks like

function wp_create_post_autosave( $post_id ) {
	$translated = _wp_translate_postdata( true );
	if ( is_wp_error( $translated ) )
		return $translated;
 
	// Only store one autosave.  If there is already an autosave, overwrite it.
	if ( $old_autosave = wp_get_post_autosave( $post_id ) ) {
		$new_autosave = _wp_post_revision_fields( $_POST, true );
		$new_autosave['ID'] = $old_autosave->ID;
		return wp_update_post( $new_autosave );
	}
 
	// Otherwise create the new autosave as a special post revision
	// return _wp_put_post_revision( $_POST, true );
	return edit_post();
}

By now, WordPress doesn’t save the annoying revisions and autosave works well. I think the only disadvantage is that it hacks WordPress core code. Once you upgrade WordPress, you have to change the 2 lines.

Tags: WordPress

This entry was posted on Saturday, February 21st, 2009 at 5:09 pm and is filed under Blog. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.