Merge pull request #481 from lautis/lateral

Lateral expressions for PostgreSQL

6 files changed, 40 insertions, 1 deletions

diff --git a/lib/arel/nodes/select_core.rb b/lib/arel/nodes/select_core.rb
index 264fa46591..fa1c026107 100644
--- a/lib/arel/nodes/select_core.rb
+++ b/lib/arel/nodes/select_core.rb
@@ -10,7 +10,7 @@ module Arel
         @source         = JoinSource.new nil
         @top            = nil
 
-        # http://savage.net.au/SQL/sql-92.bnf.html#set%20quantifier
+        # https://ronsavage.github.io/SQL/sql-92.bnf.html#set%20quantifier
         @set_quantifier = nil
         @projections    = []
         @wheres         = []
diff --git a/lib/arel/nodes/unary.rb b/lib/arel/nodes/unary.rb
index 5711d91dce..e458d87ab3 100644
--- a/lib/arel/nodes/unary.rb
+++ b/lib/arel/nodes/unary.rb
@@ -28,6 +28,7 @@ module Arel
       Group
       GroupingElement
       GroupingSet
+      Lateral
       Limit
       Lock
       Not
diff --git a/lib/arel/select_manager.rb b/lib/arel/select_manager.rb
index a88dcd320c..0f3b0dc6a0 100644
--- a/lib/arel/select_manager.rb
+++ b/lib/arel/select_manager.rb
@@ -202,6 +202,11 @@ module Arel
     end
     alias :minus :except
 
+    def lateral table_name = nil
+      base = table_name.nil? ? ast : as(table_name)
+      Nodes::Lateral.new(base)
+    end
+
     def with *subqueries
       if subqueries.first.is_a? Symbol
         node_class = Nodes.const_get("With#{subqueries.shift.to_s.capitalize}")
diff --git a/lib/arel/visitors/depth_first.rb b/lib/arel/visitors/depth_first.rb
index 5416a285f5..b3bbc9bd40 100644
--- a/lib/arel/visitors/depth_first.rb
+++ b/lib/arel/visitors/depth_first.rb
@@ -25,6 +25,7 @@ module Arel
       alias :visit_Arel_Nodes_GroupingElement   :unary
       alias :visit_Arel_Nodes_Grouping          :unary
       alias :visit_Arel_Nodes_Having            :unary
+      alias :visit_Arel_Nodes_Lateral           :unary
       alias :visit_Arel_Nodes_Limit             :unary
       alias :visit_Arel_Nodes_Not               :unary
       alias :visit_Arel_Nodes_Offset            :unary
diff --git a/lib/arel/visitors/postgresql.rb b/lib/arel/visitors/postgresql.rb
index 2a935e4318..047f71aaa6 100644
--- a/lib/arel/visitors/postgresql.rb
+++ b/lib/arel/visitors/postgresql.rb
@@ -5,6 +5,7 @@ module Arel
       CUBE = 'CUBE'
       ROLLUP = 'ROLLUP'
       GROUPING_SET = 'GROUPING SET'
+      LATERAL = 'LATERAL'
 
       private
 
@@ -69,6 +70,23 @@ module Arel
         grouping_array_or_grouping_element o, collector
       end
 
+      def visit_Arel_Nodes_Lateral o, collector
+        collector << LATERAL
+        collector << SPACE
+        grouping_parentheses o, collector
+      end
+
+      # Used by Lateral visitor to enclose select queries in parentheses
+      def grouping_parentheses o, collector
+        if o.expr.is_a? Nodes::SelectStatement
+          collector << "("
+          visit o.expr, collector
+          collector << ")"
+        else
+          visit o.expr, collector
+        end
+      end
+
       # Utilized by GroupingSet, Cube & RollUp visitors to
       # handle grouping aggregation semantics
       def grouping_array_or_grouping_element o, collector
diff --git a/test/visitors/test_postgres.rb b/test/visitors/test_postgres.rb
index beae117ef5..b28c0f3c18 100644
--- a/test/visitors/test_postgres.rb
+++ b/test/visitors/test_postgres.rb
@@ -51,6 +51,20 @@ module Arel
         assert_equal 'SELECT DISTINCT', compile(core)
       end
 
+      it 'encloses LATERAL queries in parens' do
+        subquery = @table.project(:id).where(@table[:name].matches('foo%'))
+        compile(subquery.lateral).must_be_like %{
+          LATERAL (SELECT id FROM "users" WHERE "users"."name" ILIKE 'foo%')
+        }
+      end
+
+      it 'produces LATERAL queries with alias' do
+        subquery = @table.project(:id).where(@table[:name].matches('foo%'))
+        compile(subquery.lateral('bar')).must_be_like %{
+          LATERAL (SELECT id FROM "users" WHERE "users"."name" ILIKE 'foo%') bar
+        }
+      end
+
       describe "Nodes::Matches" do
         it "should know how to visit" do
           node = @table[:name].matches('foo%')