Delay building arel relation as long as possible for improved introspection

4 files changed, 137 insertions, 139 deletions

diff --git a/activerecord/lib/active_record/relation/calculation_methods.rb b/activerecord/lib/active_record/relation/calculation_methods.rb
index 5246c7bc5d..e6f62ee49a 100644
--- a/activerecord/lib/active_record/relation/calculation_methods.rb
+++ b/activerecord/lib/active_record/relation/calculation_methods.rb
@@ -25,7 +25,7 @@ module ActiveRecord
       operation = operation.to_s.downcase
 
       if operation == "count"
-        joins = @relation.joins(relation)
+        joins = arel.joins(arel)
         if joins.present? && joins =~ /LEFT OUTER/i
           distinct = true
           column_name = @klass.primary_key if column_name == :all
@@ -40,7 +40,7 @@ module ActiveRecord
       distinct = options[:distinct] || distinct
       column_name = :all if column_name.blank? && operation == "count"
 
-      if @relation.send(:groupings).any?
+      if arel.send(:groupings).any?
         return execute_grouped_calculation(operation, column_name)
       else
         return execute_simple_calculation(operation, column_name, distinct)
@@ -63,7 +63,7 @@ module ActiveRecord
     end
 
     def execute_grouped_calculation(operation, column_name) #:nodoc:
-      group_attr      = @relation.send(:groupings).first.value
+      group_attr      = arel.send(:groupings).first.value
       association     = @klass.reflect_on_association(group_attr.to_sym)
       associated      = association && association.macro == :belongs_to # only count belongs_to associations
       group_field     = associated ? association.primary_key_name : group_attr
@@ -165,12 +165,8 @@ module ActiveRecord
       column ? column.type_cast(value) : value
     end
 
-    def get_projection_name_from_chained_relations(relation = @relation)
-      if relation.respond_to?(:projections) && relation.projections.present?
-        relation.send(:select_clauses).join(', ')
-      elsif relation.respond_to?(:relation)
-        get_projection_name_from_chained_relations(relation.relation)
-      end
+    def get_projection_name_from_chained_relations
+      @select_values.join(", ") if @select_values.present?
     end
 
   end
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index c3e5f27838..3668b0997f 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -93,15 +93,15 @@ module ActiveRecord
       result = where(primary_key.in(ids)).all
 
       expected_size =
-        if @relation.taken && ids.size > @relation.taken
-          @relation.taken
+        if arel.taken && ids.size > arel.taken
+          arel.taken
         else
           ids.size
         end
 
       # 11 ids with limit 3, offset 9 should give 2 results.
-      if @relation.skipped && (ids.size - @relation.skipped < expected_size)
-        expected_size = ids.size - @relation.skipped
+      if arel.skipped && (ids.size - arel.skipped < expected_size)
+        expected_size = ids.size - arel.skipped
       end
 
       if result.size == expected_size
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index 5d7bf0b7bc..c07eca44e3 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -1,68 +1,42 @@
 module ActiveRecord
   module QueryMethods
-
-    def preload(*associations)
-      spawn.tap {|r| r.preload_associations += Array.wrap(associations) }
-    end
-
-    def includes(*associations)
-      spawn.tap {|r| r.includes_associations += Array.wrap(associations) }
-    end
-
-    def eager_load(*associations)
-      spawn.tap {|r| r.eager_load_associations += Array.wrap(associations) }
-    end
-
-    def readonly(status = true)
-      spawn.tap {|r| r.readonly = status }
-    end
-
-    def create_with(attributes = {})
-      spawn.tap {|r| r.create_with_attributes = attributes }
-    end
-
-    def select(selects)
-      if selects.present?
-        relation = spawn(@relation.project(selects))
-        relation.readonly = @relation.joins(relation).present? ? false : @readonly
-        relation
-      else
-        spawn
+    extend ActiveSupport::Concern
+
+    included do
+      (ActiveRecord::Relation::ASSOCIATION_METHODS + ActiveRecord::Relation::MULTI_VALUE_METHODS).each do |query_method|
+        attr_accessor :"#{query_method}_values"
+
+        class_eval <<-CEVAL
+          def #{query_method}(*args)
+            spawn.tap do |new_relation|
+              new_relation.#{query_method}_values ||= []
+              value = args.size > 1 ? [args] : Array.wrap(args)
+              new_relation.#{query_method}_values += value
+            end
+          end
+        CEVAL
       end
-    end
-
-    def from(from)
-      from.present? ? spawn(@relation.from(from)) : spawn
-    end
 
-    def having(*args)
-      return spawn if args.blank?
+      ActiveRecord::Relation::SINGLE_VALUE_METHODS.each do |query_method|
+        attr_accessor :"#{query_method}_value"
 
-      if [String, Hash, Array].include?(args.first.class)
-        havings = @klass.send(:merge_conditions, args.size > 1 ? Array.wrap(args) : args.first)
-      else
-        havings = args.first
+        class_eval <<-CEVAL
+          def #{query_method}(value = true)
+            spawn.tap do |new_relation|
+              new_relation.#{query_method}_value = value
+            end
+          end
+        CEVAL
       end
-
-      spawn(@relation.having(havings))
-    end
-
-    def group(groups)
-      groups.present? ? spawn(@relation.group(groups)) : spawn
-    end
-
-    def order(orders)
-      orders.present? ? spawn(@relation.order(orders)) : spawn
     end
 
     def lock(locks = true)
+      relation = spawn
       case locks
-      when String
-        spawn(@relation.lock(locks))
-      when TrueClass, NilClass
-        spawn(@relation.lock)
+      when String, TrueClass, NilClass
+        spawn.tap {|new_relation| new_relation.lock_value = locks || true }
       else
-        spawn
+        spawn.tap {|new_relation| new_relation.lock_value = false }
       end
     end
 
@@ -70,7 +44,7 @@ module ActiveRecord
       relation = spawn
       relation.instance_variable_set(:@orders, nil)
 
-      order_clause = @relation.send(:order_clauses).join(', ')
+      order_clause = arel.send(:order_clauses).join(', ')
       if order_clause.present?
         relation.order(reverse_sql_order(order_clause))
       else
@@ -78,39 +52,74 @@ module ActiveRecord
       end
     end
 
-    def limit(limits)
-      limits.present? ? spawn(@relation.take(limits)) : spawn
+    def arel
+      @arel ||= build_arel
     end
 
-    def offset(offsets)
-      offsets.present? ? spawn(@relation.skip(offsets)) : spawn
-    end
+    def build_arel
+      arel = table
 
-    def on(join)
-      spawn(@relation.on(join))
-    end
+      @joins_values.each do |j|
+        next if j.blank?
 
-    def joins(join, join_type = nil)
-      return spawn if join.blank?
+        @implicit_readonly = true
 
-      join_relation = case join
-      when String
-        @relation.join(join)
-      when Hash, Array, Symbol
-        if @klass.send(:array_of_strings?, join)
-          @relation.join(join.join(' '))
+        case j
+        when Relation::JoinOperation
+          arel = arel.join(j.relation, j.join_class).on(j.on)
+        when Hash, Array, Symbol
+          if @klass.send(:array_of_strings?, j)
+            arel = arel.join(j.join(' '))
+          else
+            arel = arel.join(@klass.send(:build_association_joins, j))
+          end
         else
-          @relation.join(@klass.send(:build_association_joins, join))
+          arel = arel.join(j)
         end
-      else
-        @relation.join(join, join_type)
       end
 
-      spawn(join_relation).tap { |r| r.readonly = true }
+      @where_values.each do |where|
+        if conditions = build_where(where)
+          arel = conditions.is_a?(String) ? arel.where(conditions) : arel.where(*conditions)
+        end
+      end
+
+      @having_values.each do |where|
+        if conditions = build_where(where)
+          arel = conditions.is_a?(String) ? arel.having(conditions) : arel.having(*conditions)
+        end
+      end
+
+      arel = arel.take(@limit_value) if @limit_value.present?
+      arel = arel.skip(@offset_value) if @offset_value.present?
+
+      @group_values.each do |g|
+        arel = arel.group(g) if g.present?
+      end
+
+      @order_values.each do |o|
+        arel = arel.order(o) if o.present?
+      end
+
+      @select_values.each do |s|
+        @implicit_readonly = false
+        arel = arel.project(s) if s.present?
+      end
+
+      arel = arel.from(@from_value) if @from_value.present?
+
+      case @lock_value
+      when TrueClass
+        arel = arel.lock
+      when String
+        arel = arel.lock(@lock_value)
+      end
+
+      arel
     end
 
-    def where(*args)
-      return spawn if args.blank?
+    def build_where(*args)
+      return if args.blank?
 
       builder = PredicateBuilder.new(Arel::Sql::Engine.new(@klass))
 
@@ -124,7 +133,7 @@ module ActiveRecord
         args.first
       end
 
-      conditions.is_a?(String) ? spawn(@relation.where(conditions)) : spawn(@relation.where(*conditions))
+      conditions
     end
 
     private
diff --git a/activerecord/lib/active_record/relation/spawn_methods.rb b/activerecord/lib/active_record/relation/spawn_methods.rb
index 4ecee8c634..66eae69d92 100644
--- a/activerecord/lib/active_record/relation/spawn_methods.rb
+++ b/activerecord/lib/active_record/relation/spawn_methods.rb
@@ -1,49 +1,51 @@
 module ActiveRecord
   module SpawnMethods
-    def spawn(relation = @relation)
-      relation = Relation.new(@klass, relation)
-      relation.readonly = @readonly
-      relation.preload_associations = @preload_associations
-      relation.eager_load_associations = @eager_load_associations
-      relation.includes_associations = @includes_associations
-      relation.create_with_attributes = @create_with_attributes
-      relation.table = table
+    def spawn(arel_table = self.table)
+      relation = Relation.new(@klass, arel_table)
+
+      (Relation::ASSOCIATION_METHODS + Relation::MULTI_VALUE_METHODS).each do |query_method|
+        relation.send(:"#{query_method}_values=", send(:"#{query_method}_values"))
+      end
+
+      Relation::SINGLE_VALUE_METHODS.each do |query_method|
+        relation.send(:"#{query_method}_value=", send(:"#{query_method}_value"))
+      end
+
       relation
     end
 
     def merge(r)
       raise ArgumentError, "Cannot merge a #{r.klass.name} relation with #{@klass.name} relation" if r.klass != @klass
 
-      merged_relation = spawn(table).eager_load(r.eager_load_associations).preload(r.preload_associations).includes(r.includes_associations)
-      merged_relation.readonly = r.readonly
-
-      [self.relation, r.relation].each do |arel|
-        merged_relation = merged_relation.
-          joins(arel.joins(arel)).
-          group(arel.groupings).
-          limit(arel.taken).
-          offset(arel.skipped).
-          select(arel.send(:select_clauses)).
-          from(arel.sources).
-          having(arel.havings).
-          lock(arel.locked)
-      end
+      merged_relation = spawn.eager_load(r.eager_load_values).preload(r.preload_values).includes(r.includes_values)
+
+      merged_relation.readonly_value = r.readonly_value unless merged_relation.readonly_value
+      merged_relation.limit_value = r.limit_value unless merged_relation.limit_value
+      merged_relation.lock_value = r.lock_value unless merged_relation.lock_value
+
+      merged_relation = merged_relation.
+        joins(r.joins_values).
+        group(r.group_values).
+        offset(r.offset_value).
+        select(r.select_values).
+        from(r.from_value).
+        having(r.having_values)
 
-      relation_order = r.send(:order_clause)
-      merged_order = relation_order.present? ? relation_order : order_clause
-      merged_relation = merged_relation.order(merged_order)
+      relation_order = r.order_values
+      merged_order = relation_order.present? ? relation_order : order_values
+      merged_relation.order_values = merged_order
 
-      merged_relation.create_with_attributes = @create_with_attributes
+      merged_relation.create_with_value = @create_with_value
 
-      if @create_with_attributes && r.create_with_attributes
-        merged_relation.create_with_attributes = @create_with_attributes.merge(r.create_with_attributes)
+      if @create_with_value && r.create_with_value
+        merged_relation.create_with_value = @create_with_value.merge(r.create_with_value)
       else
-        merged_relation.create_with_attributes = r.create_with_attributes || @create_with_attributes
+        merged_relation.create_with_value = r.create_with_value || @create_with_value
       end
 
-      merged_wheres = @relation.wheres
+      merged_wheres = @where_values
 
-      r.wheres.each do |w|
+      r.where_values.each do |w|
         if w.is_a?(Arel::Predicates::Equality)
           merged_wheres = merged_wheres.reject {|p| p.is_a?(Arel::Predicates::Equality) && p.operand1.name == w.operand1.name }
         end
@@ -51,32 +53,23 @@ module ActiveRecord
         merged_wheres << w
       end
 
-      merged_relation.where(*merged_wheres)
+      merged_relation.where_values = merged_wheres
+
+      merged_relation
     end
 
     alias :& :merge
 
     def except(*skips)
       result = Relation.new(@klass, table)
-      result.table = table
 
-      [:eager_load, :preload, :includes].each do |load_method|
-        result = result.send(load_method, send(:"#{load_method}_associations"))
+      (Relation::ASSOCIATION_METHODS + Relation::MULTI_VALUE_METHODS).each do |method|
+        result.send(:"#{method}_values=", send(:"#{method}_values")) unless skips.include?(method)
       end
 
-      result.readonly = self.readonly unless skips.include?(:readonly)
-      result.create_with_attributes = @create_with_attributes unless skips.include?(:create_with)
-
-      result = result.joins(@relation.joins(@relation)) unless skips.include?(:joins)
-      result = result.group(@relation.groupings) unless skips.include?(:group)
-      result = result.limit(@relation.taken) unless skips.include?(:limit)
-      result = result.offset(@relation.skipped) unless skips.include?(:offset)
-      result = result.select(@relation.send(:select_clauses)) unless skips.include?(:select)
-      result = result.from(@relation.sources) unless skips.include?(:from)
-      result = result.order(order_clause) unless skips.include?(:order)
-      result = result.where(*@relation.wheres) unless skips.include?(:where)
-      result = result.having(*@relation.havings) unless skips.include?(:having)
-      result = result.lock(@relation.locked) unless skips.include?(:lock)
+      Relation::SINGLE_VALUE_METHODS.each do |method|
+        result.send(:"#{method}_value=", send(:"#{method}_value")) unless skips.include?(method)
+      end
 
       result
     end