Changeset 36566 for trunk/src/wp-includes/query.php

Timestamp:

02/17/2016 10:57:33 PM (11 years ago)

Author:

boonebgorges

Message:

More performance improvements to metadata lazyloading.

Comment and term meta lazyloading for WP_Query loops, introduced in 4.4,
depended on filter callback methods belonging to WP_Query objects. This meant
storing WP_Query objects in the $wp_filter global (via add_filter()),
requiring that PHP retain the objects in memory, even when the local variables
would typically be expunged during normal garbage collection. In cases where a
large number of WP_Query objects were instantiated on a single pageload,
and/or where the contents of the WP_Query objects were quite large, serious
performance issues could result.

We skirt this problem by moving metadata lazyloading out of WP_Query. The
new WP_Metadata_Lazyloader class acts as a lazyload queue. Query instances
register items whose metadata should be lazyloaded - such as post terms, or
comments - and a WP_Metadata_Lazyloader method will intercept comment and
term meta requests to perform the cache priming. Since WP_Metadata_Lazyloader
instances are far smaller than WP_Query (containing only object IDs), and
clean up after themselves far better than the previous WP_Query methods (bp
only running their callbacks a single time for a given set of queued objects),
the resource use is decreased dramatically.

See [36525] for an earlier step in this direction.

Props lpawlik, stevegrunwell, boonebgorges.
Fixes #35816.

File:

• trunk/src/wp-includes/query.php (modified) (4 diffs)

trunk/src/wp-includes/query.php

@@ -3606 +3606 @@
                         $this->posts = array_map( 'get_post', $this->posts );
 
-
-                if ( $q['update_post_term_cache'] ) {
-                        add_filter( 'get_term_metadata', array( $this, 'lazyload_term_meta' ), 10, 2 );
-                }
-
                 if ( ! $q['suppress_filters'] ) {
                         /**
@@ -3739 +3734 @@
                 // If comments have been fetched as part of the query, make sure comment meta lazy-loading is set up.
                 if ( ! empty( $this->comments ) ) {
-                        add_filter( 'get_comment_metadata', array( $this, 'lazyload_comment_meta' ), 10, 2 );
+                        wp_queue_comments_for_comment_meta_lazyload( $this->comments );
                 }
 
@@ -3769 +3764 @@
                         $this->post_count = 0;
                         $this->posts = array();
+                }
+
+                if ( $q['update_post_term_cache'] ) {
+                        wp_queue_posts_for_term_meta_lazyload( $this->posts );
                 }
 
@@ -4835 +4834 @@
 
         /**
-         * Lazy-loads termmeta for located posts.
-         *
-         * As a rule, term queries (`get_terms()` and `wp_get_object_terms()`) prime the metadata cache for matched
-         * terms by default. However, this can cause a slight performance penalty, especially when that metadata is
-         * not actually used. In the context of a `WP_Query` instance, we're able to avoid this potential penalty.
-         * `update_object_term_cache()`, called from `update_post_caches()`, does not 'update_term_meta_cache'.
-         * Instead, the first time `get_term_meta()` is called from within a `WP_Query` loop, the current method
-         * detects the fact, and then primes the metadata cache for all terms attached to all posts in the loop,
-         * with a single database query.
-         *
-         * This method is public so that it can be used as a filter callback. As a rule, there is no need to invoke it
-         * directly, from either inside or outside the `WP_Query` object.
+         * Lazyload term meta for posts in the loop.
          *
          * @since 4.4.0
-         * @access public
-         *
-         * @param mixed $check  The `$check` param passed from the 'get_term_metadata' hook.
-         * @param int  $term_id ID of the term whose metadata is being cached.
-         * @return mixed In order not to short-circuit `get_metadata()`. Generally, this is `null`, but it could be
-         *               another value if filtered by a plugin.
+         * @deprecated 4.5.0 See wp_queue_posts_for_term_meta_lazyload().
+         *
+         * @param mixed $check
+         * @param int   $term_id
+         * @return mixed
          */
         public function lazyload_term_meta( $check, $term_id ) {
-                // We can only lazyload if the entire post object is present.
-                $posts = array();
-                foreach ( $this->posts as $post ) {
-                        if ( $post instanceof WP_Post ) {
-                                $posts[] = $post;
-                        }
-                }
-
-                if ( ! empty( $posts ) ) {
-                        // Fetch cached term_ids for each post. Keyed by term_id for faster lookup.
-                        $term_ids = array();
-                        foreach ( $posts as $post ) {
-                                $taxonomies = get_object_taxonomies( $post->post_type );
-                                foreach ( $taxonomies as $taxonomy ) {
-                                        // Term cache should already be primed by 'update_post_term_cache'.
-                                        $terms = get_object_term_cache( $post->ID, $taxonomy );
-                                        if ( false !== $terms ) {
-                                                foreach ( $terms as $term ) {
-                                                        if ( ! isset( $term_ids[ $term->term_id ] ) ) {
-                                                                $term_ids[ $term->term_id ] = 1;
-                                                        }
-                                                }
-                                        }
-                                }
-                        }
-
-                        /*
-                         * Only update the metadata cache for terms belonging to these posts if the term_id passed
-                         * to `get_term_meta()` matches one of those terms. This prevents a single call to
-                         * `get_term_meta()` from priming metadata for all `WP_Query` objects.
-                         */
-                        if ( isset( $term_ids[ $term_id ] ) ) {
-                                update_termmeta_cache( array_keys( $term_ids ) );
-                                remove_filter( 'get_term_metadata', array( $this, 'lazyload_term_meta' ), 10, 2 );
-                        }
-                }
-
-                // If no terms were found, there's no need to run this again.
-                if ( empty( $term_ids ) ) {
-                        remove_filter( 'get_term_metadata', array( $this, 'lazyload_term_meta' ), 10, 2 );
-                }
-
+                _deprecated_function( __METHOD__, '4.5.0' );
                 return $check;
         }
 
         /**
-         * Lazy-load comment meta when inside of a `WP_Query` loop.
-         *
-         * This method is public so that it can be used as a filter callback. As a rule, there is no need to invoke it
-         * directly, from either inside or outside the `WP_Query` object.
+         * Lazyload comment meta for comments in the loop.
          *
          * @since 4.4.0
-         *
-         * @param mixed $check     The `$check` param passed from the 'get_comment_metadata' hook.
-         * @param int  $comment_id ID of the comment whose metadata is being cached.
-         * @return mixed The original value of `$check`, to not affect 'get_comment_metadata'.
+         * @deprecated 4.5.0 See wp_queue_comments_for_comment_meta_lazyload().
+         *
+         * @param mixed $check
+         * @param int   $comment_id
+         * @return mixed
          */
         public function lazyload_comment_meta( $check, $comment_id ) {
-                // Don't use `wp_list_pluck()` to avoid by-reference manipulation.
-                $comment_ids = array();
-                if ( is_array( $this->comments ) ) {
-                        foreach ( $this->comments as $comment ) {
-                                $comment_ids[] = $comment->comment_ID;
-                        }
-                }
-
-                /*
-                 * Only update the metadata cache for comments belonging to these posts if the comment_id passed
-                 * to `get_comment_meta()` matches one of those comments. This prevents a single call to
-                 * `get_comment_meta()` from priming metadata for all `WP_Query` objects.
-                 */
-                if ( in_array( $comment_id, $comment_ids ) ) {
-                        update_meta_cache( 'comment', $comment_ids );
-                        remove_filter( 'get_comment_metadata', array( $this, 'lazyload_comment_meta' ), 10, 2 );
-                } elseif ( empty( $comment_ids ) ) {
-                        remove_filter( 'get_comment_metadata', array( $this, 'lazyload_comment_meta' ), 10, 2 );
-                }
-
+                _deprecated_function( __METHOD__, '4.5.0' );
                 return $check;
         }