Delete post revisions on post publish

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Is it possible to delete post/page revisions from the database when a post/page is published?

11/05/12 Answer: See the plugin below by bueltge

I want to do this on a site with 5,000 posts and 125,000 comments; it’s on a VPS and can handle the wp_posts table size – before I deleted all revisions, the table was 1.5 gigs – but I still want to keep the overall database size to a minimum by preventing revisions.

But, the client tells me he lost a big post due to a browser freeze, so: is it possible to delete post/page revisions from the database for each post/page when it is published?

What hook would be used? Is save_post the correct one? http://codex.wordpress.org/Plugin_API/Action_Reference/save_post

I have the autosave parameter set in wp-config.php, but according to the docs, that autosaves the post/page as it is being worked on, and overwrites each autosave.

What I want to do is have revisions accumulate for drafts – however many, depending on how many times “Save” and “Update” are used by the author – but once the draft is published, delete all revisions. There will only be revisions for the one post, but rather than try and parse the post_ID, the SQL query can run through all posts.

This is what I’m trying in functions.php, but I get a Call to a member function query() on a non-object error.

function delete_revisions_on_publish( $post_id ) {

    if ( !wp_is_post_revision( $post_id ) ) {

remove_action('save_post', 'delete_revisions_on_publish');

    $wpdb->query( 
    $wpdb->prepare( 
    "DELETE a,b,c
    FROM wp_posts a
    LEFT JOIN wp_term_relationships b ON (a.ID = b.object_id)
    LEFT JOIN wp_postmeta c ON (a.ID = c.post_id)
    WHERE a.post_type="revision" "
        )
);
        }
}
add_action( 'save_post', 'delete_revisions_on_publish' );

3 Answers
3

I think a small plugin with the hook ‘publish_posts’ is enough. But I dont know about a core function to delete revisions and I use a query with WP functions. The source is untested, written only for this post.

<?php
/**
 * Plugin Name: WPSE71248 Delete Revisions on Publish Posts
 * Plugin URI:  http://wordpress.stackexchange.com/questions/71248/
 * Description: 
 * Version:     1.0.0
 * Author:      Frank Bültge
 * Author URI:  http://bueltge.de
 * License:     GPLv3
 */

! defined( 'ABSPATH' ) and exit;

add_action( 'publish_post', 'fb_remove_revisions' );

function fb_remove_revisions( $post_id = FALSE ) {

    $post_id = (int) $post_id;

    $revisions="";
    // Get the revisions
    $revisions = new WP_Query( array(
        'post_status'    => 'inherit',
        'post_type'      => 'revision',
        'showposts'      => -1,
        'posts_per_page' => -1,
        'post_parent'    => $post_id
    ) );

    if ( empty( $revisions ) )
        return $post_id;

    // Remove the revisions the non-core-way
    global $wpdb;
    foreach ( $revisions->posts as $revision ) {
        $query = $wpdb->prepare(
            "
            DELETE FROM $wpdb->posts 
            WHERE ID = %d
            AND post_parent = %d
            ",
            $revision->ID, 
            $post_id
        );
        $wpdb->query( $query );
    }

    return $post_id;
}

Alternative use the download from Gist 4017151

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