Ticket #18536: advanced-post-cache.php

<?php

/*
Plugin Name: Advanced Post Caching
Description: Cache post queries.
Version: 0.2
Author: Automattic
Author URI: http://automattic.com/
*/

class Advanced_Post_Cache {
        var $CACHE_GROUP_PREFIX = 'advanced_post_cache_';

        // Flag for temp (within one page load) turning invalidations on and off
        // @see dont_clear_advanced_post_cache()
        // @see do_clear_advanced_post_cache()
        // Used to prevent invalidation during new comment
        var $do_flush_cache = true;

        // Flag for preventing multiple invalidations in a row: clean_post_cache() calls itself recursively for post children.
        var $need_to_flush_cache = true; // Currently disabled

/* Per cache-clear data */
        var $cache_incr = 0; // Increments the cache group (advanced_post_cache_0, advanced_post_cache_1, ...)
        var $cache_group = ''; // CACHE_GROUP_PREFIX . $cache_incr

/* Per query data */
        var $cache_key = ''; // md5 of current SQL query
        var $all_post_ids = false; // IDs of all posts current SQL query returns
        var $cached_post_ids = array(); // subset of $all_post_ids whose posts are currently in cache
        var $cached_posts = array();
        var $found_posts = false; // The result of the FOUND_ROWS() query
        var $cache_func = 'wp_cache_add'; // Turns to set if there seems to be inconsistencies

        function __construct() {
                wp_cache_add_group_prefix_map( $this->CACHE_GROUP_PREFIX, 'advanced_post_cache' );

                $this->cache_incr = wp_cache_get( 'advanced_post_cache', 'cache_incrementors' ); // Get and construct current cache group name
                if ( !is_numeric( $this->cache_incr ) ) {
                        $now = time();
                        wp_cache_set( 'advanced_post_cache', $now, 'cache_incrementors' );
                        $this->cache_incr = $now;
                }
                $this->cache_group = $this->CACHE_GROUP_PREFIX . $this->cache_incr;

                add_filter( 'posts_request', array( &$this, 'posts_request' ) ); // Short circuits if cached
                add_filter( 'posts_results', array( &$this, 'posts_results' ) ); // Collates if cached, primes cache if not

                add_filter( 'post_limits_request', array( &$this, 'post_limits_request' ), 999, 2 ); // Checks to see if we need to worry about found_posts

                add_filter( 'found_posts_query', array( &$this, 'found_posts_query' ) ); // Short circuits if cached
                add_filter( 'found_posts', array( &$this, 'found_posts' ) ); // Reads from cache if cached, primes cache if not
        }

/* Advanced Post Cache API */

        /**
         * Flushes the cache by incrementing the cache group
         */
        function flush_cache() {
                // Cache flushes have been disabled
                if ( !$this->do_flush_cache )
                        return;

                // Bail on post preview
                if ( is_admin() && isset( $_POST['wp-preview'] ) && 'dopreview' == $_POST['wp-preview'] )
                        return;

                // Bail on autosave
                if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
                        return;

                // We already flushed once this page load, and have not put anything into the cache since.
                // OTHER processes may have put something into the cache!  In theory, this could cause stale caches.
                // We do this since clean_post_cache() (which fires the action this method attaches to) is called RECURSIVELY for all descendants.
//              if ( !$this->need_to_flush_cache )
//                      return;

                $this->cache_incr = wp_cache_incr( 'advanced_post_cache', 1, 'cache_incrementors' );
                if ( 10 < strlen( $this->cache_incr ) ) {
                        wp_cache_set( 'advanced_post_cache', 0, 'cache_incrementors' );
                        $this->cache_incr = 0;
                }
                $this->cache_group = $this->CACHE_GROUP_PREFIX . $this->cache_incr;
                $this->need_to_flush_cache = false;
        }


/* Cache Reading/Priming Functions */

        /** 
         * Determines (by hash of SQL) if query is cached.
         * If cached: Return query of needed post IDs.
         * Otherwise: Returns query unchanged.
         */
        function posts_request( $sql ) {
                global $wpdb;

                $this->cache_key = md5( $sql ); // init
                $this->all_post_ids = wp_cache_get( $this->cache_key, $this->cache_group );
                if ( 'NA' !== $this->found_posts )
                        $this->found_posts = wp_cache_get( "{$this->cache_key}_found", $this->cache_group );

                if ( $this->all_post_ids xor $this->found_posts )
                        $this->cache_func = 'wp_cache_set';
                else
                        $this->cache_func = 'wp_cache_add';

                $this->cached_post_ids = array(); // re-init
                $this->cached_posts = array(); // re-init

                // Query is cached
                if ( $this->found_posts && is_array( $this->all_post_ids ) ) {
                        $this->cached_posts = array_filter( wp_cache_get_multi( array( 'posts' => $this->all_post_ids ) ) );
                        foreach ( $this->cached_posts as $post ) { 
                                if ( !empty( $post ) )
                                        $this->cached_post_ids[] = $post->ID;
                        } 
                        $uncached_post_ids = array_diff( $this->all_post_ids, $this->cached_post_ids );

                        if ( $uncached_post_ids )
                                return "SELECT * FROM $wpdb->posts WHERE ID IN(" . join( ',', array_map( 'absint', $uncached_post_ids ) ) . ")";
                        return '';
                }

                return $sql;
        }

        /** 
         * If cached: Collates posts returned by SQL query with posts that are already cached.  Orders correctly.
         * Otherwise: Primes cache with data for current posts WP_Query.
         */
        function posts_results( $posts ) {
                if ( $this->found_posts && is_array( $this->all_post_ids ) ) { // is cached
                        $collated_posts = array();
                        foreach ( $this->cached_posts as $post )
                                $posts[] = $post;
        
                        foreach ( $posts as $post ) {
                                $loc = array_search( $post->ID, $this->all_post_ids );
                                if ( is_numeric( $loc ) && -1 < $loc )
                                        $collated_posts[$loc] = $post;
                        }
                        ksort( $collated_posts );
                        return array_values( $collated_posts );
                }

                $post_ids = array();
                foreach ( $posts as $post )
                        $post_ids[] = $post->ID;

                if ( !$post_ids )
                        return array();

                call_user_func( $this->cache_func, $this->cache_key, $post_ids, $this->cache_group );
                $this->need_to_flush_cache = true;

                return $posts;
        }

        /**
         * If $limits is empty, WP_Query never calls the found_rows stuff, so we set $this->found_rows to 'NA'
         */
        function post_limits_request( $limits, &$query ) {
                if ( empty( $limits ) || ( isset( $query->query_vars['no_found_rows'] ) && $query->query_vars['no_found_rows'] ) )
                        $this->found_posts = 'NA';
                else
                        $this->found_posts = false; // re-init
                return $limits;
        }

        /**
         * If cached: Blanks SELECT FOUND_ROWS() query.  This data is already stored in cache.
         * Otherwise: Returns query unchanged.
         */
        function found_posts_query( $sql ) {
                if ( $this->found_posts && is_array( $this->all_post_ids ) ) // is cached
                        return '';
                return $sql;
        }

        /**
         * If cached: Returns cached result of FOUND_ROWS() query.
         * Otherwise: Returs result unchanged
         */
        function found_posts( $found_posts ) {
                if ( $this->found_posts && is_array( $this->all_post_ids ) ) // is cached
                        return (int) $this->found_posts;

                call_user_func( $this->cache_func, "{$this->cache_key}_found", (int) $found_posts, $this->cache_group );
                $this->need_to_flush_cache = true;

                return $found_posts;
        }
}

global $advanced_post_cache_object;
$advanced_post_cache_object = new Advanced_Post_Cache;

function clear_advanced_post_cache() {
        global $advanced_post_cache_object;
        $advanced_post_cache_object->flush_cache();
}

function do_clear_advanced_post_cache() {
        $GLOBALS['advanced_post_cache_object']->do_flush_cache = true;
}

function dont_clear_advanced_post_cache() {
        $GLOBALS['advanced_post_cache_object']->do_flush_cache = false;
}

add_action( 'clean_term_cache', 'clear_advanced_post_cache' );
add_action( 'clean_post_cache', 'clear_advanced_post_cache' );

// Don't clear Advanced Post Cache for a new comment - temp core hack
// http://core.trac.wordpress.org/ticket/15565
add_action( 'wp_updating_comment_count', 'dont_clear_advanced_post_cache' );
add_action( 'wp_update_comment_count'  , 'do_clear_advanced_post_cache'   );