Ticket #28146: 28146.7

diff --git a/src/wp-admin/includes/export.php b/src/wp-admin/includes/export.php
index 6d01a2c..b200c0d 100644
--- a/src/wp-admin/includes/export.php
+++ b/src/wp-admin/includes/export.php
@@ -42,6 +42,7 @@ function export_wp( $args = array() ) {
         */
        do_action( 'export_wp', $args );
 
+       // Set export file name
        $sitename = sanitize_key( get_bloginfo( 'name' ) );
        if ( ! empty( $sitename ) ) {
                $sitename .= '.';
@@ -59,48 +60,98 @@ function export_wp( $args = array() ) {
         */
        $filename = apply_filters( 'export_wp_filename', $wp_filename, $sitename, $date );
 
+       // Set content headers
        header( 'Content-Description: File Transfer' );
        header( 'Content-Disposition: attachment; filename=' . $filename );
        header( 'Content-Type: text/xml; charset=' . get_option( 'blog_charset' ), true );
 
-       if ( 'all' != $args['content'] && post_type_exists( $args['content'] ) ) {
-               $ptype = get_post_type_object( $args['content'] );
-               if ( ! $ptype->can_export )
-                       $args['content'] = 'post';
+       $query_args = array(
+               'post_status' => 'any',
+               'posts_per_page' => -1
+       );
 
-               $where = $wpdb->prepare( "{$wpdb->posts}.post_type = %s", $args['content'] );
+       if ( 'all' != $args['content'] ) {
+               $post_types = (array) $args['content'];
+
+               $query_args['post_type'] = array();
+
+               foreach( $post_types as $post_type ) {
+                       $post_type_object = get_post_type_object( $post_type );
+
+                       if ( $post_type_object && $post_type_object->can_export ) {
+                               $query_args['post_type'][] = $post_type;
+                       }
+               }
+
+               if ( empty( $query_args['post_type'] ) ) {
+                       $query_args['post_type'] = 'post';
+               }
        } else {
-               $post_types = get_post_types( array( 'can_export' => true ) );
-               $esses = array_fill( 0, count($post_types), '%s' );
-               $where = $wpdb->prepare( "{$wpdb->posts}.post_type IN (" . implode( ',', $esses ) . ')', $post_types );
+               $query_args['post_type'] = array_values( get_post_types( array( 'can_export' => true ) ) );
        }
 
-       if ( $args['status'] && ( 'post' == $args['content'] || 'page' == $args['content'] ) )
-               $where .= $wpdb->prepare( " AND {$wpdb->posts}.post_status = %s", $args['status'] );
-       else
-               $where .= " AND {$wpdb->posts}.post_status != 'auto-draft'";
+       if ( $args['status'] && ( 'post' == $args['content'] || 'page' == $args['content'] ) ) {
+               $query_args['post_status'] = $args['status'];
+       }
 
-       $join = '';
        if ( $args['category'] && 'post' == $args['content'] ) {
                if ( $term = term_exists( $args['category'], 'category' ) ) {
-                       $join = "INNER JOIN {$wpdb->term_relationships} ON ({$wpdb->posts}.ID = {$wpdb->term_relationships}.object_id)";
-                       $where .= $wpdb->prepare( " AND {$wpdb->term_relationships}.term_taxonomy_id = %d", $term['term_taxonomy_id'] );
+                       $query_args['tax_query'] = array(
+                               array(
+                                       'taxonomy' => 'category',
+                                       'terms' => $term->term_id,
+                                       'include_children' => false
+                               )
+                       );
                }
        }
 
-       if ( 'post' == $args['content'] || 'page' == $args['content'] || 'attachment' == $args['content'] ) {
+       if ( 'post' == $args['content'] || 'page' == $args['content'] ) {
                if ( $args['author'] )
-                       $where .= $wpdb->prepare( " AND {$wpdb->posts}.post_author = %d", $args['author'] );
+                       $query_args['author'] = (int) $args['author'];
+
+               $date_query = array();
+
 
                if ( $args['start_date'] )
-                       $where .= $wpdb->prepare( " AND {$wpdb->posts}.post_date >= %s", date( 'Y-m-d', strtotime($args['start_date']) ) );
+                       $date_query[]['after'] = $args['start_date'];
 
-               if ( $args['end_date'] )
-                       $where .= $wpdb->prepare( " AND {$wpdb->posts}.post_date < %s", date( 'Y-m-d', strtotime('+1 month', strtotime($args['end_date'])) ) );
+               if ( $args['end_date'] ) {
+                       $date_query[]['before'] =  '@' . strtotime( '+1 month', strtotime( $args['end_date'] ) );
+               }
+
+
+               if ( ! empty( $date_query ) ) {
+                       $query_args['date_query'] = $date_query;
+               }
        }
 
-       // Grab a snapshot of post IDs, just in case it changes during the export.
-       $post_ids = $wpdb->get_col( "SELECT ID FROM {$wpdb->posts} $join WHERE $where" );
+       /**
+        * Filter WP_Query arguments for which posts to export.
+        *
+        * @todo Update since
+        * @since 4.X
+        *
+        * @param array $query_args An array of WP_Query arguments.
+        * @param array $args An array of export arguments.
+        */
+       $query_args = apply_filters( 'export_wp_query_args', $query_args, $args );
+
+       $query_args['fields'] = 'ids';
+
+       $post_ids = get_posts( $query_args );
+
+       /**
+        * Filter Post IDs to be exported.
+        *
+        * @todo Update since
+        * @since 4.X
+        *
+        * @param array $post_ids An array of Post IDs to export.
+        * @param array $query_args An array of WP_Query arguments.
+        * @param array $args An array of export arguments.
+        */
+       $post_ids = apply_filters( 'export_wp_post_ids', $post_ids, $query_args, $args );
 
        /*
         * Get the requested terms ready, empty unless posts filtered by category
@@ -111,29 +162,36 @@ function export_wp( $args = array() ) {
                $cat = get_term( $term['term_id'], 'category' );
                $cats = array( $cat->term_id => $cat );
                unset( $term, $cat );
-       } elseif ( 'all' == $args['content'] ) {
+       } else if ( 'all' == $args['content'] ) {
                $categories = (array) get_categories( array( 'get' => 'all' ) );
                $tags = (array) get_tags( array( 'get' => 'all' ) );
 
                $custom_taxonomies = get_taxonomies( array( '_builtin' => false ) );
                $custom_terms = (array) get_terms( $custom_taxonomies, array( 'get' => 'all' ) );
 
-               // Put categories in order with no child going before its parent.
-               while ( $cat = array_shift( $categories ) ) {
-                       if ( $cat->parent == 0 || isset( $cats[$cat->parent] ) )
-                               $cats[$cat->term_id] = $cat;
-                       else
-                               $categories[] = $cat;
+               // Put categories in order with no child going before its parent
+               if( $categories ) {
+                       while ( $cat = array_shift( $categories ) ) {
+                               if ( $cat->parent == 0 || isset( $cats[$cat->parent] ) ) {
+                                       $cats[$cat->term_id] = $cat;
+                               } else {
+                                       $categories[] = $cat;
+                               }
+                       }
                }
 
-               // Put terms in order with no child going before its parent.
-               while ( $t = array_shift( $custom_terms ) ) {
-                       if ( $t->parent == 0 || isset( $terms[$t->parent] ) )
-                               $terms[$t->term_id] = $t;
-                       else
-                               $custom_terms[] = $t;
+               // Put terms in order with no child going before its parent
+               if( $custom_terms ) {
+                       while ( $t = array_shift( $custom_terms ) ) {
+                               if ( $t->parent == 0 || isset( $terms[$t->parent] ) ) {
+                                       $terms[$t->term_id] = $t;
+                               } else {
+                                       $custom_terms[] = $t;
+                               }
+                       }
                }
 
+               // Clean up
                unset( $categories, $custom_taxonomies, $custom_terms );
        }
 
@@ -401,24 +459,27 @@ function export_wp( $args = array() ) {
        do_action( 'rss2_head' );
        ?>
 
-<?php if ( $post_ids ) {
-       /**
-        * @global WP_Query $wp_query
-        */
-       global $wp_query;
-
-       // Fake being in the loop.
-       $wp_query->in_the_loop = true;
-
-       // Fetch 20 posts at a time rather than loading the entire table into memory.
-       while ( $next_posts = array_splice( $post_ids, 0, 20 ) ) {
-       $where = 'WHERE ID IN (' . join( ',', $next_posts ) . ')';
-       $posts = $wpdb->get_results( "SELECT * FROM {$wpdb->posts} $where" );
-
-       // Begin Loop.
-       foreach ( $posts as $post ) {
-               setup_postdata( $post );
-               $is_sticky = is_sticky( $post->ID ) ? 1 : 0;
+       <?php
+       if ( $post_ids ) {
+               $posts_per_page = 20;
+
+               $wp_query_args = array(
+                       'post_type'      => 'any',
+                       'post_status'    => 'any',
+                       'posts_per_page' => $posts_per_page,
+                       'post__in'       => array_slice( $post_ids, 0, $posts_per_page )
+               );
+
+               $query = new WP_Query( $wp_query_args );
+
+               $page = 0;
+
+               // Paginate posts 20 at a time
+               while ( $query->have_posts() ) {
+                       // Begin Loop.
+                       while ( $query->have_posts() ) {
+                               $query->the_post();
+                                       $is_sticky = is_sticky( $post->ID ) ? 1 : 0;
 ?>
        <item>
                <title><?php
@@ -532,9 +593,17 @@ function export_wp( $args = array() ) {
 <?php  endforeach; ?>
        </item>
 <?php
+                       }
+
+                       // Fetch next set of posts
+                       $wp_query_args['post__in'] = array_slice( $post_ids, ( $page * $posts_per_page ), $posts_per_page );
+
+                       $query->query( $wp_query_args );
+
+                       $page++;
+               }
        }
-       }
-} ?>
+?>
 </channel>
 </rss>
 <?php