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<title>[37692] trunk: Query: Allow plugins to supply post results instead of having `WP_Query` fetch them from the database.</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/37692">37692</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/37692","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>2016-06-14 01:59:25 +0000 (Tue, 14 Jun 2016)</dd>
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<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>Query: Allow plugins to supply post results instead of having `WP_Query` fetch them from the database.

Returning a non-null value from the new `posts_pre_query` filter will cause
`WP_Query` to skip its database query, so that posts data can be provided from
elsewhere. This is useful in cases where post data may be mirrored in a
separate location, such as an external search application.

Developers should note that the `WP_Query` properties generally used to
calculate pagination - specifically, `found_posts` and `max_num_pages`, which
are determined by default in `set_found_posts()` - must be provided explicitly
when using the `posts_pre_query` filter; since `WP_Query` will not be
contacting the database, it will have no access to `SELECT FOUND_ROWS()`.
The `WP_Query` instance is passed to `posts_pre_query` by reference, so that
these properties can be set manually if needed.

Props jpdavoutian, tlovett1.
Fixes <a href="https://core.trac.wordpress.org/ticket/36687">#36687</a>.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunksrcwpincludesqueryphp">trunk/src/wp-includes/query.php</a></li>
<li><a href="#trunktestsphpunittestspostqueryphp">trunk/tests/phpunit/tests/post/query.php</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<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   2016-06-14 01:36:59 UTC (rev 37691)
+++ trunk/src/wp-includes/query.php     2016-06-14 01:59:25 UTC (rev 37692)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -3556,8 +3556,29 @@
</span><span class="cx" style="display: block; padding: 0 10px">                        $this->request = apply_filters_ref_array( 'posts_request', array( $this->request, &$this ) );
</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">+                /**
+                * Filters the posts array before the query takes place.
+                *
+                * Return a non-null value to bypass WordPress's default post queries.
+                *
+                * Filtering functions that require pagination information are encouraged to set
+                * the `found_posts` and `max_num_pages` properties of the WP_Query object,
+                * passed to the filter by reference. If WP_Query does not perform a database
+                * query, it will not have enough information to generate these values itself.
+                *
+                * @since 4.6.0
+                *
+                * @param array|null $posts Return an array of post data to short-circuit WP's query,
+                *                          or null to allow WP to run its normal queries.
+                * @param WP_Query   $this  The WP_Query instance, passed by reference.
+                */
+               $this->posts = apply_filters_ref_array( 'posts_pre_query', array( null, &$this ) );
+
</ins><span class="cx" style="display: block; padding: 0 10px">                 if ( 'ids' == $q['fields'] ) {
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                        $this->posts = $wpdb->get_col( $this->request );
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                 if ( null === $this->posts ) {
+                               $this->posts = $wpdb->get_col( $this->request );
+                       }
+
</ins><span class="cx" style="display: block; padding: 0 10px">                         $this->posts = array_map( 'intval', $this->posts );
</span><span class="cx" style="display: block; padding: 0 10px">                        $this->post_count = count( $this->posts );
</span><span class="cx" style="display: block; padding: 0 10px">                        $this->set_found_posts( $q, $limits );
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -3566,7 +3587,10 @@
</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">                if ( 'id=>parent' == $q['fields'] ) {
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                        $this->posts = $wpdb->get_results( $this->request );
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                 if ( null === $this->posts ) {
+                               $this->posts = $wpdb->get_results( $this->request );
+                       }
+
</ins><span class="cx" style="display: block; padding: 0 10px">                         $this->post_count = count( $this->posts );
</span><span class="cx" style="display: block; padding: 0 10px">                        $this->set_found_posts( $q, $limits );
</span><span class="cx" style="display: block; padding: 0 10px"> 
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -3581,54 +3605,56 @@
</span><span class="cx" style="display: block; padding: 0 10px">                        return $r;
</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">-                $split_the_query = ( $old_request == $this->request && "$wpdb->posts.*" == $fields && !empty( $limits ) && $q['posts_per_page'] < 500 );
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+         if ( null === $this->posts ) {
+                       $split_the_query = ( $old_request == $this->request && "$wpdb->posts.*" == $fields && !empty( $limits ) && $q['posts_per_page'] < 500 );
</ins><span class="cx" style="display: block; padding: 0 10px"> 
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                /**
-                * Filters whether to split the query.
-                *
-                * Splitting the query will cause it to fetch just the IDs of the found posts
-                * (and then individually fetch each post by ID), rather than fetching every
-                * complete row at once. One massive result vs. many small results.
-                *
-                * @since 3.4.0
-                *
-                * @param bool     $split_the_query Whether or not to split the query.
-                * @param WP_Query $this            The WP_Query instance.
-                */
-               $split_the_query = apply_filters( 'split_the_query', $split_the_query, $this );
-
-               if ( $split_the_query ) {
-                       // First get the IDs and then fill in the objects
-
-                       $this->request = "SELECT $found_rows $distinct $wpdb->posts.ID FROM $wpdb->posts $join WHERE 1=1 $where $groupby $orderby $limits";
-
</del><span class="cx" style="display: block; padding: 0 10px">                         /**
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                         * Filters the Post IDs SQL request before sending.
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                  * Filters whether to split the query.
</ins><span class="cx" style="display: block; padding: 0 10px">                          *
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                         * Splitting the query will cause it to fetch just the IDs of the found posts
+                        * (and then individually fetch each post by ID), rather than fetching every
+                        * complete row at once. One massive result vs. many small results.
+                        *
</ins><span class="cx" style="display: block; padding: 0 10px">                          * @since 3.4.0
</span><span class="cx" style="display: block; padding: 0 10px">                         *
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                         * @param string   $request The post ID request.
-                        * @param WP_Query $this    The WP_Query instance.
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                  * @param bool     $split_the_query Whether or not to split the query.
+                        * @param WP_Query $this            The WP_Query instance.
</ins><span class="cx" style="display: block; padding: 0 10px">                          */
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                        $this->request = apply_filters( 'posts_request_ids', $this->request, $this );
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                 $split_the_query = apply_filters( 'split_the_query', $split_the_query, $this );
</ins><span class="cx" style="display: block; padding: 0 10px"> 
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                        $ids = $wpdb->get_col( $this->request );
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                 if ( $split_the_query ) {
+                               // First get the IDs and then fill in the objects
</ins><span class="cx" style="display: block; padding: 0 10px"> 
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                        if ( $ids ) {
-                               $this->posts = $ids;
-                               $this->set_found_posts( $q, $limits );
-                               _prime_post_caches( $ids, $q['update_post_term_cache'], $q['update_post_meta_cache'] );
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                         $this->request = "SELECT $found_rows $distinct $wpdb->posts.ID FROM $wpdb->posts $join WHERE 1=1 $where $groupby $orderby $limits";
+
+                               /**
+                                * Filters the Post IDs SQL request before sending.
+                                *
+                                * @since 3.4.0
+                                *
+                                * @param string   $request The post ID request.
+                                * @param WP_Query $this    The WP_Query instance.
+                                */
+                               $this->request = apply_filters( 'posts_request_ids', $this->request, $this );
+
+                               $ids = $wpdb->get_col( $this->request );
+
+                               if ( $ids ) {
+                                       $this->posts = $ids;
+                                       _prime_post_caches( $ids, $q['update_post_term_cache'], $q['update_post_meta_cache'] );
+                               } else {
+                                       $this->posts = array();
+                               }
</ins><span class="cx" style="display: block; padding: 0 10px">                         } else {
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                                $this->posts = array();
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                         $this->posts = $wpdb->get_results( $this->request );
</ins><span class="cx" style="display: block; padding: 0 10px">                         }
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                } else {
-                       $this->posts = $wpdb->get_results( $this->request );
-                       $this->set_found_posts( $q, $limits );
</del><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">-                // Convert to WP_Post objects
-               if ( $this->posts )
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+         // Convert to WP_Post objects and set the found-post totals.
+               if ( $this->posts ) {
</ins><span class="cx" style="display: block; padding: 0 10px">                         $this->posts = array_map( 'get_post', $this->posts );
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                        $this->set_found_posts( $q, $limits );
+               }
</ins><span class="cx" style="display: block; padding: 0 10px"> 
</span><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></pre></div>
<a id="trunktestsphpunittestspostqueryphp"></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/post/query.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/tests/phpunit/tests/post/query.php  2016-06-14 01:36:59 UTC (rev 37691)
+++ trunk/tests/phpunit/tests/post/query.php    2016-06-14 01:59:25 UTC (rev 37692)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -388,4 +388,28 @@
</span><span class="cx" style="display: block; padding: 0 10px">                $actual_posts = $q->get_posts();
</span><span class="cx" style="display: block; padding: 0 10px">                $this->assertEqualSets( $requested, $actual_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">+
+       /**
+        * @ticket 36687
+        */
+       public function test_posts_pre_query_filter_should_bypass_database_query() {
+               global $wpdb;
+
+               add_filter( 'posts_pre_query', array( __CLASS__, 'filter_posts_pre_query' ) );
+
+               $num_queries = $wpdb->num_queries;
+               $q = new WP_Query( array(
+                       'fields' => 'ids',
+                       'no_found_rows' => true,
+               ) );
+
+               remove_filter( 'posts_pre_query', array( __CLASS__, 'filter_posts_pre_query' ) );
+
+               $this->assertSame( $num_queries, $wpdb->num_queries );
+               $this->assertSame( array( 12345 ), $q->posts );
+       }
+
+       public static function filter_posts_pre_query( $posts ) {
+               return array( 12345 );
+       }
</ins><span class="cx" style="display: block; padding: 0 10px"> }
</span></span></pre>
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