Ticket #33885: 33885.2.diff

src/wp-admin/includes/template-functions.php

@@ -577 +577 @@
         $post = get_post( $post );
 
         /**
-         * Filter the number of custom fields to retrieve for the drop-down
-         * in the Custom Fields meta box.
+         * Filter any pre-defined post meta keys for the Custom Fields meta box
+         * to short circuit a range query agaisnt postmeta.
          *
-         * @since 2.1.0
+     * @since 4.4.0
          *
-         * @param int $limit Number of custom fields to retrieve. Default 30.
-         */
-        $limit = apply_filters( 'postmeta_form_limit', 30 );
-        $sql = "SELECT DISTINCT meta_key
-                FROM $wpdb->postmeta
-                WHERE meta_key NOT BETWEEN '_' AND '_z'
-                HAVING meta_key NOT LIKE %s
-                ORDER BY meta_key
-                LIMIT %d";
-        $keys = $wpdb->get_col( $wpdb->prepare( $sql, $wpdb->esc_like( '_' ) . '%', $limit ) );
+         * @param array $keys Pre-defined meta keys to be used in place of a postmeta query. Default array().
+     */
+        $keys = apply_filters( 'postmeta_form_keys', array() );
+
+        if ( empty( $keys ) ) {
+                /**
+                 * Filter the number of custom fields to retrieve for the drop-down
+                 * in the Custom Fields meta box.
+                 *
+                 * @since 2.1.0
+                 *
+                 * @param int $limit Number of custom fields to retrieve. Default 30.
+                 */
+                $limit = apply_filters( 'postmeta_form_limit', 30 );
+                $sql = "SELECT DISTINCT meta_key
+                        FROM $wpdb->postmeta
+                        WHERE meta_key NOT BETWEEN '_' AND '_z'
+                        HAVING meta_key NOT LIKE %s
+                        ORDER BY meta_key
+                        LIMIT %d";
+                $keys = $wpdb->get_col( $wpdb->prepare( $sql, $wpdb->esc_like( '_' ) . '%', $limit ) );
+        }
+
         if ( $keys ) {
                 natcasesort( $keys );
                 $meta_key_input_id = 'metakeyselect';