Make union/except/intersect chainable

arel.gemspec

@@ -17,7 +17,7 @@ Gem::Specification.new do |s|
   s.rdoc_options = ["--main", "README.md"]
   s.extra_rdoc_files = ["History.txt", "MIT-LICENSE.txt", "README.md"]
 
-  s.files         = ["History.txt","MIT-LICENSE.txt","README.md","lib/arel.rb","lib/arel/alias_predication.rb","lib/arel/attributes.rb","lib/arel/attributes/attribute.rb","lib/arel/collectors/bind.rb","lib/arel/collectors/composite.rb","lib/arel/collectors/plain_string.rb","lib/arel/collectors/sql_string.rb","lib/arel/collectors/substitute_binds.rb","lib/arel/compatibility/wheres.rb","lib/arel/crud.rb","lib/arel/delete_manager.rb","lib/arel/errors.rb","lib/arel/expressions.rb","lib/arel/factory_methods.rb","lib/arel/insert_manager.rb","lib/arel/math.rb","lib/arel/nodes.rb","lib/arel/nodes/and.rb","lib/arel/nodes/ascending.rb","lib/arel/nodes/binary.rb","lib/arel/nodes/bind_param.rb","lib/arel/nodes/case.rb","lib/arel/nodes/casted.rb","lib/arel/nodes/count.rb","lib/arel/nodes/delete_statement.rb","lib/arel/nodes/descending.rb","lib/arel/nodes/equality.rb","lib/arel/nodes/extract.rb","lib/arel/nodes/false.rb","lib/arel/nodes/full_outer_join.rb","lib/arel/nodes/function.rb","lib/arel/nodes/grouping.rb","lib/arel/nodes/in.rb","lib/arel/nodes/infix_operation.rb","lib/arel/nodes/inner_join.rb","lib/arel/nodes/insert_statement.rb","lib/arel/nodes/join_source.rb","lib/arel/nodes/matches.rb","lib/arel/nodes/named_function.rb","lib/arel/nodes/node.rb","lib/arel/nodes/outer_join.rb","lib/arel/nodes/over.rb","lib/arel/nodes/regexp.rb","lib/arel/nodes/right_outer_join.rb","lib/arel/nodes/select_core.rb","lib/arel/nodes/select_statement.rb","lib/arel/nodes/sql_literal.rb","lib/arel/nodes/string_join.rb","lib/arel/nodes/table_alias.rb","lib/arel/nodes/terminal.rb","lib/arel/nodes/true.rb","lib/arel/nodes/unary.rb","lib/arel/nodes/unary_operation.rb","lib/arel/nodes/unqualified_column.rb","lib/arel/nodes/update_statement.rb","lib/arel/nodes/values.rb","lib/arel/nodes/values_list.rb","lib/arel/nodes/window.rb","lib/arel/nodes/with.rb","lib/arel/order_predications.rb","lib/arel/predications.rb","lib/arel/select_manager.rb","lib/arel/table.rb","lib/arel/tree_manager.rb","lib/arel/update_manager.rb","lib/arel/visitors.rb","lib/arel/visitors/depth_first.rb","lib/arel/visitors/dot.rb","lib/arel/visitors/ibm_db.rb","lib/arel/visitors/informix.rb","lib/arel/visitors/mssql.rb","lib/arel/visitors/mysql.rb","lib/arel/visitors/oracle.rb","lib/arel/visitors/oracle12.rb","lib/arel/visitors/postgresql.rb","lib/arel/visitors/sqlite.rb","lib/arel/visitors/to_sql.rb","lib/arel/visitors/visitor.rb","lib/arel/visitors/where_sql.rb","lib/arel/window_predications.rb"]
+  s.files = Dir["History.txt", "MIT-LICENSE.txt", "README.md", "lib/**/*"]
   s.require_paths = ["lib"]
 
   s.add_development_dependency('minitest', '~> 5.4')

lib/arel/nodes.rb

@@ -36,7 +36,8 @@
 require 'arel/nodes/regexp'
 
 # nary
-require 'arel/nodes/and'
+require 'arel/nodes/nary'
+require 'arel/nodes/set_operation'
 
 # function
 # FIXME: Function + Alias can be rewritten as a Function and Alias node.

lib/arel/nodes/binary.rb

@@ -39,11 +39,6 @@ def eql? other
       LessThanOrEqual
       NotEqual
       NotIn
-      Or
-      Union
-      UnionAll
-      Intersect
-      Except
     }.each do |name|
       const_set name, Class.new(Binary)
     end

lib/arel/nodes/and.rb → lib/arel/nodes/nary.rb

@@ -1,20 +1,17 @@
 # frozen_string_literal: true
 module Arel
   module Nodes
-    class And < Arel::Nodes::Node
+    class Nary < Arel::Nodes::Node
       attr_reader :children
 
       def initialize children
         super()
         @children = children
       end
 
-      def left
-        children.first
-      end
-
-      def right
-        children[1]
+      def initialize_copy other
+        super
+        @children = @children.map { |child| child.clone }
       end
 
       def hash
@@ -27,5 +24,12 @@ def eql? other
       end
       alias :== :eql?
     end
+
+    %w{
+      And
+      Or
+    }.each do |name|
+      const_set name, Class.new(Nary)
+    end
   end
 end

lib/arel/nodes/node.rb

@@ -28,7 +28,7 @@ def not
       # Factory method to create a Nodes::Grouping node that has an Nodes::Or
       # node as a child.
       def or right
-        Nodes::Grouping.new Nodes::Or.new(self, right)
+        Nodes::Grouping.new Nodes::Or.new [self, right]
       end
 
       ###

lib/arel/nodes/select_statement.rb

@@ -7,6 +7,7 @@ class SelectStatement < Arel::Nodes::NodeExpression
 
       def initialize cores = [SelectCore.new]
         super()
+        cores = [cores] unless Array === cores
         @cores          = cores
         @orders         = []
         @limit          = nil

lib/arel/nodes/set_operation.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+module Arel
+  module Nodes
+    class SetOperation < Nary
+      attr_reader :operation
+
+      def initialize(children, operation = nil)
+        super(children)
+        @operation = operation
+      end
+    end
+
+    %w{
+      Union
+      Intersect
+      Except
+    }.each do |name|
+      const_set name, Class.new(SetOperation)
+    end
+  end
+end

lib/arel/nodes/unary.rb

@@ -36,7 +36,6 @@ def eql? other
       On
       Ordering
       RollUp
-      Top
     }.each do |name|
       const_set(name, Class.new(Unary))
     end

lib/arel/predications.rb

@@ -212,7 +212,7 @@ def concat other
     def grouping_any method_id, others, *extras
       nodes = others.map {|expr| send(method_id, expr, *extras)}
       Nodes::Grouping.new nodes.inject { |memo,node|
-        Nodes::Or.new(memo, node)
+        Nodes::Or.new [memo, node]
       }
     end
 

lib/arel/select_manager.rb

@@ -5,11 +5,16 @@ class SelectManager < Arel::TreeManager
 
     STRING_OR_SYMBOL_CLASS = [Symbol, String]
 
-    def initialize table = nil
+    def initialize table = nil, cores = nil
       super()
-      @ast   = Nodes::SelectStatement.new
+      @ast = if cores
+        Nodes::SelectStatement.new(cores)
+      else
+        Nodes::SelectStatement.new
+      end
+
       @ctx    = @ast.cores.last
-      from table
+      from table if table
     end
 
     def initialize_copy other
@@ -182,23 +187,16 @@ def where_sql engine = Table.engine
       Nodes::SqlLiteral.new viz.accept(@ctx, Collectors::SQLString.new).value
     end
 
-    def union operation, other = nil
-      if other
-        node_class = Nodes.const_get("Union#{operation.to_s.capitalize}")
-      else
-        other = operation
-        node_class = Nodes::Union
-      end
-
-      node_class.new self.ast, other.ast
+    def union variant, other = nil
+      set_operation(:union, variant, other)
     end
 
-    def intersect other
-      Nodes::Intersect.new ast, other.ast
+    def intersect variant, other = nil
+      set_operation(:intersect, variant, other)
     end
 
-    def except other
-      Nodes::Except.new ast, other.ast
+    def except variant, other = nil
+      set_operation(:except, variant, other)
     end
     alias :minus :except
 
@@ -221,10 +219,8 @@ def with *subqueries
     def take limit
       if limit
         @ast.limit = Nodes::Limit.new(limit)
-        @ctx.top   = Nodes::Top.new(limit)
       else
         @ast.limit = nil
-        @ctx.top   = nil
       end
       self
     end
@@ -268,5 +264,17 @@ def collapse exprs, existing = nil
         create_and exprs
       end
     end
+
+    def set_operation(operation, variant, other)
+      unless other
+        other = variant
+        variant = nil
+      end
+
+      node_class = Nodes.const_get(operation.to_s.capitalize)
+      node = node_class.new([ast] + Array(other).map { |o| o.ast }, variant)
+
+      self.class.new(nil, node)
+    end
   end
 end

lib/arel/visitors/depth_first.rb

@@ -33,7 +33,6 @@ def unary o
       alias :visit_Arel_Nodes_Ordering          :unary
       alias :visit_Arel_Nodes_Ascending         :unary
       alias :visit_Arel_Nodes_Descending        :unary
-      alias :visit_Arel_Nodes_Top               :unary
       alias :visit_Arel_Nodes_UnqualifiedColumn :unary
 
       def function o
@@ -70,6 +69,8 @@ def nary o
         o.children.each { |child| visit child}
       end
       alias :visit_Arel_Nodes_And :nary
+      alias :visit_Arel_Nodes_Or :nary
+      alias :visit_Arel_Nodes_Union :nary
 
       def binary o
         visit o.left
@@ -95,7 +96,6 @@ def binary o
       alias :visit_Arel_Nodes_NotEqual           :binary
       alias :visit_Arel_Nodes_NotIn              :binary
       alias :visit_Arel_Nodes_NotRegexp          :binary
-      alias :visit_Arel_Nodes_Or                 :binary
       alias :visit_Arel_Nodes_OuterJoin          :binary
       alias :visit_Arel_Nodes_Regexp             :binary
       alias :visit_Arel_Nodes_RightOuterJoin     :binary

lib/arel/visitors/dot.rb

@@ -80,7 +80,6 @@ def unary o
       alias :visit_Arel_Nodes_Not               :unary
       alias :visit_Arel_Nodes_Offset            :unary
       alias :visit_Arel_Nodes_On                :unary
-      alias :visit_Arel_Nodes_Top               :unary
       alias :visit_Arel_Nodes_UnqualifiedColumn :unary
       alias :visit_Arel_Nodes_Preceding         :unary
       alias :visit_Arel_Nodes_Following         :unary
@@ -178,6 +177,7 @@ def nary o
         end
       end
       alias :visit_Arel_Nodes_And :nary
+      alias :visit_Arel_Nodes_Or  :nary
 
       def binary o
         visit_edge o, "left"
@@ -198,7 +198,6 @@ def binary o
       alias :visit_Arel_Nodes_Matches            :binary
       alias :visit_Arel_Nodes_NotEqual           :binary
       alias :visit_Arel_Nodes_NotIn              :binary
-      alias :visit_Arel_Nodes_Or                 :binary
       alias :visit_Arel_Nodes_Over               :binary
 
       def visit_String o

lib/arel/visitors/mssql.rb

@@ -11,13 +11,6 @@ def initialize(*)
 
       private
 
-      # `top` wouldn't really work here. I.e. User.select("distinct first_name").limit(10) would generate
-      # "select top 10 distinct first_name from users", which is invalid query! it should be
-      # "select distinct top 10 first_name from users"
-      def visit_Arel_Nodes_Top o
-        ""
-      end
-
       def visit_Arel_Visitors_MSSQL_RowNumber o, collector
         collector << "ROW_NUMBER() OVER (ORDER BY "
         inject_join(o.children, collector, ', ') << ") as _row_num"

lib/arel/visitors/mysql.rb

@@ -3,34 +3,6 @@ module Arel
   module Visitors
     class MySQL < Arel::Visitors::ToSql
       private
-      def visit_Arel_Nodes_Union o, collector, suppress_parens = false
-        unless suppress_parens
-          collector << "( "
-        end
-
-        collector =   case o.left
-                      when Arel::Nodes::Union
-                        visit_Arel_Nodes_Union o.left, collector, true
-                      else
-                        visit o.left, collector
-                      end
-
-        collector << " UNION "
-
-        collector =    case o.right
-                       when Arel::Nodes::Union
-                         visit_Arel_Nodes_Union o.right, collector, true
-                       else
-                         visit o.right, collector
-                       end
-
-        if suppress_parens
-          collector
-        else
-          collector << " )"
-        end
-      end
-
       def visit_Arel_Nodes_Bin o, collector
         collector << "BINARY "
         visit o.expr, collector

lib/arel/visitors/oracle.rb

@@ -82,7 +82,7 @@ def visit_Arel_Nodes_Offset o, collector
 
       def visit_Arel_Nodes_Except o, collector
         collector << "( "
-        collector = infix_value o, collector, " MINUS "
+        inject_join o.children, collector, " MINUS "
         collector << " )"
       end
 

lib/arel/visitors/oracle12.rb

@@ -36,7 +36,7 @@ def visit_Arel_Nodes_Offset o, collector
 
       def visit_Arel_Nodes_Except o, collector
         collector << "( "
-        collector = infix_value o, collector, " MINUS "
+        inject_join(o.children, collector, " MINUS ")
         collector << " )"
       end
 

lib/arel/visitors/sqlite.rb

@@ -4,6 +4,21 @@ module Visitors
     class SQLite < Arel::Visitors::ToSql
       private
 
+      def visit_Arel_Nodes_Union o, collector
+        join_str = o.operation ? " UNION #{o.operation.to_s.upcase} " : " UNION "
+        inject_join(o.children, collector, join_str)
+      end
+
+      # INTERSECT ALL is not supported in SQLite
+      def visit_Arel_Nodes_Intersect o, collector
+        inject_join(o.children, collector, " INTERSECT ")
+      end
+
+      # EXCEPT ALL is not supported in SQLite
+      def visit_Arel_Nodes_Except o, collector
+        inject_join(o.children, collector, " EXCEPT ")
+      end
+
       # Locks are not supported in SQLite
       def visit_Arel_Nodes_Lock o, collector
         collector