1 files changed, 6 insertions, 72 deletions
diff --git a/lib/arel/engines/sql/relations/relation.rb b/lib/arel/engines/sql/relations/relation.rb
index 78508595fd..15903412d5 100644
--- a/lib/arel/engines/sql/relations/relation.rb
+++ b/lib/arel/engines/sql/relations/relation.rb
@@ -1,86 +1,20 @@
 module Arel
   class Relation
-    def to_sql(formatter = Sql::SelectStatement.new(self))
-      formatter.select select_sql, self
-    end
-
-    def select_sql
-      if engine.adapter_name == "PostgreSQL" && !orders.blank? && using_distinct_on?
-        # PostgreSQL does not allow arbitrary ordering when using DISTINCT ON, so we work around this
-        # by wrapping the +sql+ string as a sub-select and ordering in that query.
-        order = order_clauses.join(', ').split(',').map { |s| s.strip }.reject(&:blank?)
-        order = order.zip((0...order.size).to_a).map { |s,i| "id_list.alias_#{i} #{'DESC' if s =~ /\bdesc$/i}" }.join(', ')
-
-        query = build_query \
-          "SELECT     #{select_clauses.kind_of?(::Array) ? select_clauses.join("") : select_clauses.to_s}",
-          "FROM       #{from_clauses}",
-          (joins(self)                                   unless joins(self).blank? ),
-          ("WHERE     #{where_clauses.join(" AND ")}"    unless wheres.blank?      ),
-          ("GROUP BY  #{group_clauses.join(', ')}"       unless groupings.blank?   ),
-          ("HAVING    #{having_clauses.join(', ')}"      unless havings.blank?   ),
-          ("#{locked}"                                   unless locked.blank?     )
 
-        build_query \
-          "SELECT * FROM (#{query}) AS id_list",
-          "ORDER BY #{order}",
-          ("LIMIT     #{taken}"                          unless taken.blank?       ),
-          ("OFFSET    #{skipped}"                        unless skipped.blank?     )
-
-      else
-        build_query \
-          "SELECT     #{select_clauses.join(', ')}",
-          "FROM       #{from_clauses}",
-          (joins(self)                                   unless joins(self).blank? ),
-          ("WHERE     #{where_clauses.join(" AND ")}"    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?     ),
-          ("#{locked}"                                   unless engine.adapter_name =~ /SQLite/ || locked.blank?)
-      end
+    def compiler
+      @compiler ||= "Arel::SqlCompiler::#{engine.adapter_name}Compiler".constantize.new(self)
     end
 
-    def inclusion_predicate_sql
-      "IN"
+    def to_sql(formatter = Sql::SelectStatement.new(self))
+      formatter.select compiler.select_sql, self
     end
 
     def christener
       @christener ||= Sql::Christener.new
     end
 
-  protected
-
-    def build_query(*parts)
-      parts.compact.join(" ")
-    end
-
-    def from_clauses
-      sources.blank? ? table_sql(Sql::TableReference.new(self)) : sources
-    end
-
-    def select_clauses
-      attributes.collect { |a| a.to_sql(Sql::SelectClause.new(self)) }
-    end
-
-    def where_clauses
-      wheres.collect { |w| w.to_sql(Sql::WhereClause.new(self)) }
-    end
-
-    def group_clauses
-      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
-
-    def using_distinct_on?
-      select_clauses.any? { |x| x =~ /DISTINCT ON/ }
+    def inclusion_predicate_sql
+      "IN"
     end
   end
 end