Added having to use in combination with group to filter records.

6 files changed, 29 insertions, 2 deletions

diff --git a/lib/arel/algebra/relations.rb b/lib/arel/algebra/relations.rb
index 951b69d970..9481554667 100644
--- a/lib/arel/algebra/relations.rb
+++ b/lib/arel/algebra/relations.rb
@@ -7,6 +7,7 @@ require 'arel/algebra/relations/writes'
 require 'arel/algebra/relations/operations/alias'
 require 'arel/algebra/relations/operations/from'
 require 'arel/algebra/relations/operations/group'
+require 'arel/algebra/relations/operations/having'
 require 'arel/algebra/relations/operations/join'
 require 'arel/algebra/relations/operations/order'
 require 'arel/algebra/relations/operations/project'
diff --git a/lib/arel/algebra/relations/operations/having.rb b/lib/arel/algebra/relations/operations/having.rb
new file mode 100644
index 0000000000..cd16535609
--- /dev/null
+++ b/lib/arel/algebra/relations/operations/having.rb
@@ -0,0 +1,13 @@
+module Arel
+  class Having < Compound
+    attributes :relation, :havings
+    deriving :==
+
+    def initialize(relation, *havings, &block)
+      @relation = relation
+      @havings = (havings + arguments_from_block(relation, &block)) \
+        .collect { |g| g.bind(relation) }
+    end
+  end
+end
+
diff --git a/lib/arel/algebra/relations/relation.rb b/lib/arel/algebra/relations/relation.rb
index b24e7c24d0..e848c8aa1c 100644
--- a/lib/arel/algebra/relations/relation.rb
+++ b/lib/arel/algebra/relations/relation.rb
@@ -43,7 +43,7 @@ module Arel
         join(other_relation, OuterJoin)
       end
 
-      [:where, :project, :order, :take, :skip, :group, :from].each do |operation_name|
+      [:where, :project, :order, :take, :skip, :group, :from, :having].each do |operation_name|
         class_eval <<-OPERATION, __FILE__, __LINE__
           def #{operation_name}(*arguments, &block)
             arguments.all?(&:blank?) && !block_given?? self : #{operation_name.to_s.classify}.new(self, *arguments, &block)
@@ -131,6 +131,7 @@ module Arel
       def orders;                 []  end
       def inserts;                []  end
       def groupings;              []  end
+      def havings;                []  end
       def joins(formatter = nil); nil end # FIXME
       def taken;                  nil end
       def skipped;                nil end
diff --git a/lib/arel/algebra/relations/utilities/compound.rb b/lib/arel/algebra/relations/utilities/compound.rb
index 9967472d88..1acf92fef8 100644
--- a/lib/arel/algebra/relations/utilities/compound.rb
+++ b/lib/arel/algebra/relations/utilities/compound.rb
@@ -5,7 +5,7 @@ module Arel
              :column_for, :engine, :sources, :locked,
              :to => :relation
 
-    [:attributes, :wheres, :groupings, :orders].each do |operation_name|
+    [:attributes, :wheres, :groupings, :orders, :havings].each do |operation_name|
       class_eval <<-OPERATION, __FILE__, __LINE__
         def #{operation_name}
           @#{operation_name} ||= relation.#{operation_name}.collect { |o| o.bind(self) }
diff --git a/lib/arel/engines/sql/formatters.rb b/lib/arel/engines/sql/formatters.rb
index 626803a887..e05dc3eb93 100644
--- a/lib/arel/engines/sql/formatters.rb
+++ b/lib/arel/engines/sql/formatters.rb
@@ -57,6 +57,12 @@ module Arel
       end
     end
 
+    class HavingClause < PassThrough
+      def attribute(attribute)
+        attribute
+      end
+    end
+
     class WhereCondition < Formatter
       def attribute(attribute)
         "#{quote_table_name(name_for(attribute.original_relation))}.#{quote_column_name(attribute.name)}"
diff --git a/lib/arel/engines/sql/relations/relation.rb b/lib/arel/engines/sql/relations/relation.rb
index 12b328151f..940f985358 100644
--- a/lib/arel/engines/sql/relations/relation.rb
+++ b/lib/arel/engines/sql/relations/relation.rb
@@ -17,6 +17,7 @@ module Arel
           (joins(self)                                   unless joins(self).blank? ),
           ("WHERE     #{where_clauses.join("\n\tAND ")}" unless wheres.blank?      ),
           ("GROUP BY  #{group_clauses.join(', ')}"       unless groupings.blank?   ),
+          ("HAVING    #{having_clauses.join(', ')}"      unless havings.blank?   ),
           ("#{locked}"                                   unless locked.blank?     )
 
         build_query \
@@ -32,6 +33,7 @@ module Arel
           (joins(self)                                   unless joins(self).blank? ),
           ("WHERE     #{where_clauses.join("\n\tAND ")}" unless wheres.blank?      ),
           ("GROUP BY  #{group_clauses.join(', ')}"       unless groupings.blank?   ),
+          ("HAVING    #{having_clauses.join(', ')}"      unless havings.blank?     ),
           ("ORDER BY  #{order_clauses.join(', ')}"       unless orders.blank?      ),
           ("LIMIT     #{taken}"                          unless taken.blank?       ),
           ("OFFSET    #{skipped}"                        unless skipped.blank?     ),
@@ -69,6 +71,10 @@ module Arel
       groupings.collect { |g| g.to_sql(Sql::GroupClause.new(self)) }
     end
 
+    def having_clauses
+      havings.collect { |g| g.to_sql(Sql::HavingClause.new(self)) }
+    end
+
     def order_clauses
       orders.collect { |o| o.to_sql(Sql::OrderClause.new(self)) }
     end