From 3864fada7202c2a37bb31d47a489c297f6c5dbf5 Mon Sep 17 00:00:00 2001
From: Dane Springmeyer <dane@dbsgeo.com>
Date: Fri, 19 Jul 2013 15:46:01 -0400
Subject: [PATCH] pass string by const ref

---
 include/mapnik/layer.hpp | 2 +-
 src/layer.cpp            | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/mapnik/layer.hpp b/include/mapnik/layer.hpp
index a259b9741..985de5ce9 100644
--- a/include/mapnik/layer.hpp
+++ b/include/mapnik/layer.hpp
@@ -167,7 +167,7 @@ public:
     /*!
      * @param column Set the field rendering of this layer is grouped by.
      */
-    void set_group_by(std::string column);
+    void set_group_by(std::string const& column);
 
     /*!
      * @return The field rendering of this layer is grouped by.
diff --git a/src/layer.cpp b/src/layer.cpp
index a2352cc2e..95c2513f5 100644
--- a/src/layer.cpp
+++ b/src/layer.cpp
@@ -236,7 +236,7 @@ bool layer::cache_features() const
     return cache_features_;
 }
 
-void layer::set_group_by(std::string column)
+void layer::set_group_by(std::string const& column)
 {
     group_by_ = column;
 }