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<title>[34704] trunk: Improve lazyloading of term metadata in `WP_Query` loops.</title>
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<dt style="float: left; width: 6em; font-weight: bold">Revision</dt> <dd><a style="font-weight: bold" href="https://core.trac.wordpress.org/changeset/34704">34704</a><script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","description":"Review this Commit","action":{"@type":"ViewAction","url":"https://core.trac.wordpress.org/changeset/34704","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>boonebgorges</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2015-09-29 21:59:44 +0000 (Tue, 29 Sep 2015)</dd>
</dl>
<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>Improve lazyloading of term metadata in `WP_Query` loops.
<a href="https://core.trac.wordpress.org/changeset/34529">[34529]</a> 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 <a href="https://core.trac.wordpress.org/ticket/34047">#34047</a>.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunksrcwpincludesdefaultfiltersphp">trunk/src/wp-includes/default-filters.php</a></li>
<li><a href="#trunksrcwpincludesqueryphp">trunk/src/wp-includes/query.php</a></li>
<li><a href="#trunksrcwpincludestaxonomyfunctionsphp">trunk/src/wp-includes/taxonomy-functions.php</a></li>
<li><a href="#trunktestsphpunitteststermmetaphp">trunk/tests/phpunit/tests/term/meta.php</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunksrcwpincludesdefaultfiltersphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/default-filters.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/default-filters.php 2015-09-29 21:43:04 UTC (rev 34703)
+++ trunk/src/wp-includes/default-filters.php 2015-09-29 21:59:44 UTC (rev 34704)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -201,7 +201,6 @@
</span><span class="cx" style="display: block; padding: 0 10px"> add_filter( 'xmlrpc_pingback_error', 'xmlrpc_pingback_error' );
</span><span class="cx" style="display: block; padding: 0 10px"> add_filter( 'title_save_pre', 'trim' );
</span><span class="cx" style="display: block; padding: 0 10px"> add_filter( 'get_comment_metadata', 'wp_lazyload_comment_meta', 10, 2 );
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-add_filter( 'get_term_metadata', 'wp_lazyload_term_meta', 10, 2 );
</del><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> add_filter( 'http_request_host_is_external', 'allowed_http_request_hosts', 10, 2 );
</span><span class="cx" style="display: block; padding: 0 10px">
</span></span></pre></div>
<a id="trunksrcwpincludesqueryphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/query.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/query.php 2015-09-29 21:43:04 UTC (rev 34703)
+++ trunk/src/wp-includes/query.php 2015-09-29 21:59:44 UTC (rev 34704)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1303,6 +1303,15 @@
</span><span class="cx" style="display: block; padding: 0 10px"> public $thumbnails_cached = false;
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> /**
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ * 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;
+
+ /**
</ins><span class="cx" style="display: block; padding: 0 10px"> * Cached list of search stopwords.
</span><span class="cx" style="display: block; padding: 0 10px"> *
</span><span class="cx" style="display: block; padding: 0 10px"> * @since 3.7.0
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -3541,6 +3550,11 @@
</span><span class="cx" style="display: block; padding: 0 10px"> if ( $this->posts )
</span><span class="cx" style="display: block; padding: 0 10px"> $this->posts = array_map( 'get_post', $this->posts );
</span><span class="cx" style="display: block; padding: 0 10px">
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+
+ if ( $q['update_post_term_cache'] ) {
+ add_action( 'get_term_metadata', array( $this, 'lazyload_term_meta' ), 10, 2 );
+ }
+
</ins><span class="cx" style="display: block; padding: 0 10px"> if ( ! $q['suppress_filters'] ) {
</span><span class="cx" style="display: block; padding: 0 10px"> /**
</span><span class="cx" style="display: block; padding: 0 10px"> * Filter the raw post results array, prior to status checks.
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -4722,6 +4736,86 @@
</span><span class="cx" style="display: block; padding: 0 10px"> $this->setup_postdata( $this->post );
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+
+ /**
+ * 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;
+ }
</ins><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> /**
</span></span></pre></div>
<a id="trunksrcwpincludestaxonomyfunctionsphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/taxonomy-functions.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/taxonomy-functions.php 2015-09-29 21:43:04 UTC (rev 34703)
+++ trunk/src/wp-includes/taxonomy-functions.php 2015-09-29 21:59:44 UTC (rev 34704)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1589,63 +1589,6 @@
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> /**
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- * Lazy-loads termmeta when inside of a `WP_Query` loop.
- *
- * 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` loop, 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 function detects the fact, and then primes the metadata cache for
- * all terms attached to all posts in the loop, with a single database query.
- *
- * @since 4.4.0
- *
- * @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 null In order not to short-circuit `get_metadata()`.
- */
-function wp_lazyload_term_meta( $check, $term_id ) {
- global $wp_query;
-
- if ( $wp_query instanceof WP_Query && ! empty( $wp_query->posts ) && $wp_query->get( 'update_post_term_cache' ) ) {
- // We can only lazyload if the entire post object is present.
- $posts = array();
- foreach ( $wp_query->posts as $post ) {
- if ( $post instanceof WP_Post ) {
- $posts[] = $post;
- }
- }
-
- if ( empty( $posts ) ) {
- return;
- }
-
- // 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 ) {
- // No extra queries. 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;
- }
- }
- }
- }
- }
-
- if ( $term_ids ) {
- update_termmeta_cache( array_keys( $term_ids ) );
- }
- }
-
- return $check;
-}
-
-/**
</del><span class="cx" style="display: block; padding: 0 10px"> * Check if Term exists.
</span><span class="cx" style="display: block; padding: 0 10px"> *
</span><span class="cx" style="display: block; padding: 0 10px"> * Formerly is_term(), introduced in 2.3.0.
</span></span></pre></div>
<a id="trunktestsphpunitteststermmetaphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/tests/phpunit/tests/term/meta.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/tests/phpunit/tests/term/meta.php 2015-09-29 21:43:04 UTC (rev 34703)
+++ trunk/tests/phpunit/tests/term/meta.php 2015-09-29 21:59:44 UTC (rev 34704)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -145,6 +145,58 @@
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ /**
+ * @ticket 34073
+ */
+ public function test_term_meta_should_be_lazy_loaded_only_for_the_queries_in_which_the_term_has_posts() {
+ global $wpdb;
+
+ $posts = $this->factory->post->create_many( 3, array( 'post_status' => 'publish' ) );
+ register_taxonomy( 'wptests_tax', 'post' );
+ $terms = $this->factory->term->create_many( 6, array( 'taxonomy' => 'wptests_tax' ) );
+
+ wp_set_object_terms( $posts[0], array( $terms[0], $terms[1] ), 'wptests_tax' );
+ wp_set_object_terms( $posts[1], array( $terms[2], $terms[3] ), 'wptests_tax' );
+ wp_set_object_terms( $posts[2], array( $terms[0], $terms[4], $terms[5] ), 'wptests_tax' );
+
+ foreach ( $terms as $t ) {
+ add_term_meta( $t, 'foo', 'bar' );
+ }
+
+ $q0 = new WP_Query( array( 'p' => $posts[0] ) );
+ $q1 = new WP_Query( array( 'p' => $posts[1] ) );
+ $q2 = new WP_Query( array( 'p' => $posts[2] ) );
+
+ /*
+ * $terms[0] belongs to both $posts[0] and $posts[2], so `get_term_meta( $terms[0] )` should prime
+ * the cache for term matched by $q0 and $q2.
+ */
+
+ // First request will hit the database.
+ $num_queries = $wpdb->num_queries;
+
+ // Prime caches.
+ $this->assertSame( 'bar', get_term_meta( $terms[0], 'foo', true ) );
+
+ // Two queries: one for $q0 and one for $q2.
+ $num_queries += 2;
+ $this->assertSame( $num_queries, $wpdb->num_queries );
+
+ // Next requests should be in cache.
+ $this->assertSame( 'bar', get_term_meta( $terms[1], 'foo', true ) );
+ $this->assertSame( 'bar', get_term_meta( $terms[4], 'foo', true ) );
+ $this->assertSame( 'bar', get_term_meta( $terms[5], 'foo', true ) );
+ $this->assertSame( $num_queries, $wpdb->num_queries );
+
+ // Querying for $terms[2] will prime $terms[3] as well.
+ $this->assertSame( 'bar', get_term_meta( $terms[2], 'foo', true ) );
+ $num_queries++;
+ $this->assertSame( $num_queries, $wpdb->num_queries );
+
+ $this->assertSame( 'bar', get_term_meta( $terms[3], 'foo', true ) );
+ $this->assertSame( $num_queries, $wpdb->num_queries );
+ }
+
</ins><span class="cx" style="display: block; padding: 0 10px"> public function test_adding_term_meta_should_bust_get_terms_cache() {
</span><span class="cx" style="display: block; padding: 0 10px"> $terms = $this->factory->term->create_many( 2, array( 'taxonomy' => 'wptests_tax' ) );
</span><span class="cx" style="display: block; padding: 0 10px">
</span></span></pre>
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