Changeset 34704 for trunk/src/wp-includes/query.php

Timestamp:

09/29/2015 09:59:44 PM (9 years ago)

Author:

boonebgorges

Message:

Improve lazyloading of term metadata in WP_Query loops.

[34529] introduced lazyloading for the metadata belonging to terms matching
posts in the main WP_Query. The current changeset improves this technique
in the following ways:

• Term meta lazyloading is now performed on the results of all WP_Query queries, not just the main query.
• Fewer global variable touches and greater encapsulation.
• The logic for looping through posts to identify terms is now only performed once per WP_Query.

Props dlh, boonebgorges.
See #34047.

File:

• trunk/src/wp-includes/query.php (modified) (3 diffs)

trunk/src/wp-includes/query.php

@@ -1302 +1302 @@
      */
      public $thumbnails_cached = false;
+
+    /**
+     * Whether the term meta cache for matched posts has been primed.
+     *
+     * @since 4.4.0
+     * @access protected
+     * @var bool
+     */
+    public $updated_term_meta_cache = false;
 
     /**
@@ -3542 +3551 @@
             $this->posts = array_map( 'get_post', $this->posts );
 
+
+        if ( $q['update_post_term_cache'] ) {
+            add_action( 'get_term_metadata', array( $this, 'lazyload_term_meta' ), 10, 2 );
+        }
+
         if ( ! $q['suppress_filters'] ) {
             /**
@@ -4723 +4737 @@
         }
     }
+
+    /**
+     * 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.
+     *
+     * @since 4.4.0
+     * @access public
+     *
+     * @param null $check   The `$check` param passed from the 'pre_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.
+     */
+    public function lazyload_term_meta( $check, $term_id ) {
+        /*
+         * We only do this once per `WP_Query` instance.
+         * Can't use `remove_action()` because of non-unique object hashes.
+         */
+        if ( $this->updated_term_meta_cache ) {
+            return $check;
+        }
+
+        // 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;
+            }
+        }
+        $_p = array();
+        foreach ( $posts as $post ) {
+            $_p[] = $post->ID;
+        }
+
+        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 ) );
+                $this->updated_term_meta_cache = true;
+            }
+        }
+
+        // If no terms were found, there's no need to run this again.
+        if ( empty( $term_ids ) ) {
+            $this->updated_term_meta_cache = true;
+        }
+
+        return $check;
+    }
 }