From 3d862034cdff3fde03c1bca90ce95a9505d6c04d Mon Sep 17 00:00:00 2001
From: Dane Springmeyer <dane@dbsgeo.com>
Date: Tue, 12 Jul 2011 01:48:36 +0000
Subject: [PATCH] allow '[field] is null' syntax to work with the understanding
 this may have unintended consequences and we should likely ultimately replace
 with proper 'is' equality support for nulls - track issue at
 http://trac.mapnik.org/ticket/794

---
 include/mapnik/value.hpp                     | 7 ++++++-
 plugins/input/postgis/postgis_featureset.cpp | 6 +++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/mapnik/value.hpp b/include/mapnik/value.hpp
index 9870581a7..95943a165 100644
--- a/include/mapnik/value.hpp
+++ b/include/mapnik/value.hpp
@@ -106,8 +106,10 @@ struct equals
 
     bool operator() (value_null, value_null) const
     {
-        return false;
+        // this changed from false to true - see http://trac.mapnik.org/ticket/794
+        return true;
     }
+
 };
       
 struct not_equals
@@ -143,18 +145,21 @@ struct not_equals
 
     bool operator() (value_null, value_null) const
     {
+        // TODO - needs review http://trac.mapnik.org/ticket/794
         return false;
     }
 
     template <typename T>
     bool operator() (value_null, const T &) const
     {
+        // TODO - needs review http://trac.mapnik.org/ticket/794
         return false;
     }
 
     template <typename T>
     bool operator() (const T &, value_null) const
     {
+        // TODO - needs review http://trac.mapnik.org/ticket/794
         return false;
     }
 };
diff --git a/plugins/input/postgis/postgis_featureset.cpp b/plugins/input/postgis/postgis_featureset.cpp
index de86ab9ae..78c085759 100644
--- a/plugins/input/postgis/postgis_featureset.cpp
+++ b/plugins/input/postgis/postgis_featureset.cpp
@@ -108,7 +108,11 @@ feature_ptr postgis_featureset::next()
         {
             std::string name = rs_->getFieldName(pos);
 
-            if (!rs_->isNull(pos))
+            if (rs_->isNull(pos))
+            {
+                boost::put(*feature,name,mapnik::value_null());
+            }
+            else
             {
                 const char* buf = rs_->getValue(pos);
                 int oid = rs_->getTypeOID(pos);