Add support for aggregates in row views

Add a few aggregates implementations (min, max, distinct)
Use distinct to get the GB homepage in a single DB trip
Fix lessthan operation on variable types to be the right way round as it now matters

3 files changed, 87 insertions, 0 deletions

diff --git a/project2/common/aggregates/distinct.cpp b/project2/common/aggregates/distinct.cpp
new file mode 100644
index 0000000..85e69c2
--- /dev/null
+++ b/project2/common/aggregates/distinct.cpp
@@ -0,0 +1,28 @@
+#include "../aggregate.h"
+#include <boost/foreach.hpp>
+
+class Distinct : public SetAggregate {
+	public:
+		Distinct(ScriptNodePtr s) :
+			SetAggregate(s)
+		{
+		}
+		void reset() const
+		{
+			result.clear();
+		}
+		void pushValue(const VariableType & v) const
+		{
+			result.insert(v);
+		}
+		void onResultValues(const SetAggregate::UseAgg & u) const
+		{
+			BOOST_FOREACH(const VariableType & v, result) {
+				u(v);
+			}
+		}
+	private:
+		mutable std::set<VariableType> result;
+};
+
+DECLARE_LOADER("distinct", Distinct);
diff --git a/project2/common/aggregates/max.cpp b/project2/common/aggregates/max.cpp
new file mode 100644
index 0000000..a6e528a
--- /dev/null
+++ b/project2/common/aggregates/max.cpp
@@ -0,0 +1,27 @@
+#include "../aggregate.h"
+
+class Max : public ValueAggregate {
+	public:
+		Max(ScriptNodePtr s) : ValueAggregate(s) { }
+
+		void reset() const
+		{
+			result = VariableType();
+		}
+		void pushValue(const VariableType & v) const
+		{
+			if (result < v) {
+				result = v;
+			}
+		}
+		VariableType resultValue() const
+		{
+			return result;
+		}
+	private:
+		mutable VariableType result;
+};
+
+DECLARE_LOADER("max", Max);
+
+
diff --git a/project2/common/aggregates/min.cpp b/project2/common/aggregates/min.cpp
new file mode 100644
index 0000000..14c63ae
--- /dev/null
+++ b/project2/common/aggregates/min.cpp
@@ -0,0 +1,32 @@
+#include "../aggregate.h"
+
+class Min : public ValueAggregate {
+	public:
+		Min(ScriptNodePtr s) :
+			ValueAggregate(s),
+			first(true)
+		{
+		}
+		void reset() const
+		{
+			result = VariableType();
+			first = true;
+		}
+		void pushValue(const VariableType & v) const
+		{
+			if (first || v < result) {
+				result = v;
+			}
+			first = false;
+		}
+		VariableType resultValue() const
+		{
+			return result;
+		}
+	private:
+		mutable VariableType result;
+		mutable bool first;
+};
+
+DECLARE_LOADER("min", Min);
+