Improve support for ordering WP_Query results by postmeta.

`WP_Meta_Query` clauses now support a 'name' parameter. When building a
`WP_Query` object, the value of 'orderby' can reference this 'name', so that
it's possible to order by any clause in a meta_query, not just the first one
(as when using 'orderby=meta_value'). This improvement also makes it possible
to order by multiple meta query clauses (or by any other eligible field plus
a meta query clause), using the array syntax for 'orderby' introduced in [29027].

Props Funkatronic, boonebgorges.
Fixes #31045.
Built from https://develop.svn.wordpress.org/trunk@31312


git-svn-id: http://core.svn.wordpress.org/trunk@31293 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/meta.php

@@ -933,10 +933,20 @@ class WP_Meta_Query {
 	 */
 	protected $table_aliases = array();
 
+	/**
+	 * A flat list of clauses, keyed by clause 'name'.
+	 *
+	 * @since 4.2.0
+	 * @var array
+	 */
+	protected $clauses = array();
+
 	/**
 	 * Constructor.
 	 *
 	 * @since 3.2.0
+	 * @since 4.2.0 Introduced the `$name` parameter, for improved `$orderby` support in the parent query.
+	 *
 	 * @access public
 	 *
 	 * @param array $meta_query {
@@ -957,6 +967,8 @@ class WP_Meta_Query {
 	 *                               comparisons. Accepts 'NUMERIC', 'BINARY', 'CHAR', 'DATE',
 	 *                               'DATETIME', 'DECIMAL', 'SIGNED', 'TIME', or 'UNSIGNED'.
 	 *                               Default is 'CHAR'.
+	 *         @type string $name    Optional. A unique identifier for the clause. If provided, `$name` can be
+	 *                               referenced in the `$orderby` parameter of the parent query.
 	 *     }
 	 * }
 	 */
@@ -1374,6 +1386,15 @@ class WP_Meta_Query {
 		// Save the alias to this clause, for future siblings to find.
 		$clause['alias'] = $alias;
 
+		// Determine the data type.
+		$_meta_type = isset( $clause['type'] ) ? $clause['type'] : '';
+		$meta_type  = $this->get_cast_for_type( $_meta_type );
+		$clause['cast'] = $meta_type;
+
+		// Store the clause in our flat array.
+		$clause_name = isset( $clause['name'] ) ? $clause['name'] : $clause['alias'];
+		$this->clauses[ $clause_name ] =& $clause;
+
 		// Next, build the WHERE clause.
 
 		// meta_key.
@@ -1388,7 +1409,6 @@ class WP_Meta_Query {
 		// meta_value.
 		if ( array_key_exists( 'value', $clause ) ) {
 			$meta_value = $clause['value'];
-			$meta_type = $this->get_cast_for_type( isset( $clause['type'] ) ? $clause['type'] : '' );
 
 			if ( in_array( $meta_compare, array( 'IN', 'NOT IN', 'BETWEEN', 'NOT BETWEEN' ) ) ) {
 				if ( ! is_array( $meta_value ) ) {
@@ -1450,6 +1470,21 @@ class WP_Meta_Query {
 		return $sql_chunks;
 	}
 
+	/**
+	 * Get a flattened list of sanitized meta clauses, indexed by clause 'name'.
+	 *
+	 * This array should be used for clause lookup, as when the table alias and CAST type must be determined for
+	 * a value of 'orderby' corresponding to a meta clause.
+	 *
+	 * @since 4.2.0
+	 * @access public
+	 *
+	 * @return array
+	 */
+	public function get_clauses() {
+		return $this->clauses;
+	}
+
 	/**
 	 * Identify an existing table alias that is compatible with the current
 	 * query clause.

wp-includes/query.php

@@ -2233,8 +2233,9 @@ class WP_Query {
 
 		$primary_meta_key = '';
 		$primary_meta_query = false;
-		if ( ! empty( $this->meta_query->queries ) ) {
+		$meta_clauses = $this->meta_query->get_clauses();
-			$primary_meta_query = reset( $this->meta_query->queries );
+		if ( ! empty( $meta_clauses ) ) {
+			$primary_meta_query = reset( $meta_clauses );
 
 			if ( ! empty( $primary_meta_query['key'] ) ) {
 				$primary_meta_key = $primary_meta_query['key'];
@@ -2243,6 +2244,7 @@ class WP_Query {
 
 			$allowed_keys[] = 'meta_value';
 			$allowed_keys[] = 'meta_value_num';
+			$allowed_keys   = array_merge( $allowed_keys, array_keys( $meta_clauses ) );
 		}
 
 		if ( ! in_array( $orderby, $allowed_keys ) ) {
@@ -2260,29 +2262,36 @@ class WP_Query {
 			case 'ID':
 			case 'menu_order':
 			case 'comment_count':
-				$orderby = "$wpdb->posts.{$orderby}";
+				$orderby_clause = "$wpdb->posts.{$orderby}";
 				break;
 			case 'rand':
-				$orderby = 'RAND()';
+				$orderby_clause = 'RAND()';
 				break;
 			case $primary_meta_key:
 			case 'meta_value':
 				if ( ! empty( $primary_meta_query['type'] ) ) {
-					$sql_type = $this->meta_query->get_cast_for_type( $primary_meta_query['type'] );
+					$orderby_clause = "CAST({$primary_meta_query['alias']}.meta_value AS {$primary_meta_query['cast']})";
-					$orderby = "CAST($wpdb->postmeta.meta_value AS {$sql_type})";
 				} else {
-					$orderby = "$wpdb->postmeta.meta_value";
+					$orderby_clause = "{$primary_meta_query['alias']}.meta_value";
 				}
 				break;
 			case 'meta_value_num':
-				$orderby = "$wpdb->postmeta.meta_value+0";
+				$orderby_clause = "{$primary_meta_query['alias']}.meta_value+0";
 				break;
 			default:
-				$orderby = "$wpdb->posts.post_" . $orderby;
+				if ( array_key_exists( $orderby, $meta_clauses ) ) {
+					// $orderby corresponds to a meta_query clause.
+					$meta_clause = $meta_clauses[ $orderby ];
+					$orderby_clause = "CAST({$meta_clause['alias']}.meta_value AS {$meta_clause['cast']})";
+				} else {
+					// Default: order by post field.
+					$orderby_clause = "$wpdb->posts.post_" . sanitize_key( $orderby );
+				}
+
 				break;
 		}
 
-		return $orderby;
+		return $orderby_clause;
 	}
 
 	/**
@@ -2813,6 +2822,12 @@ class WP_Query {
 
 		$where .= $search . $whichauthor . $whichmimetype;
 
+		if ( ! empty( $this->meta_query->queries ) ) {
+			$clauses = $this->meta_query->get_sql( 'post', $wpdb->posts, 'ID', $this );
+			$join   .= $clauses['join'];
+			$where  .= $clauses['where'];
+		}
+
 		$rand = ( isset( $q['orderby'] ) && 'rand' === $q['orderby'] );
 		if ( ! isset( $q['order'] ) ) {
 			$q['order'] = $rand ? '' : 'DESC';
@@ -3030,12 +3045,6 @@ class WP_Query {
 			$where .= ')';
 		}
 
-		if ( !empty( $this->meta_query->queries ) ) {
-			$clauses = $this->meta_query->get_sql( 'post', $wpdb->posts, 'ID', $this );
-			$join .= $clauses['join'];
-			$where .= $clauses['where'];
-		}
-
 		/*
 		 * Apply filters on where and join prior to paging so that any
 		 * manipulations to them are reflected in the paging by day queries.

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.2-alpha-31311';
+$wp_version = '4.2-alpha-31312';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.