Ticket #10905: 10905.diff

wp-includes/meta.php

@@ -30 +30 @@
 
         $meta_value = maybe_serialize( stripslashes_deep($meta_value) );
 
+        // prevent duplicates
+        if ( $wpdb->get_var( $wpdb->prepare(
+                "SELECT COUNT(*) FROM $table WHERE meta_key = %s AND meta_value = %s AND $column = %d",
+                $meta_key, $meta_value, $object_id ) ) )
+                return false;
+
         $wpdb->insert( $table, array(
                 $column => $object_id,
                 'meta_key' => $meta_key,