From fca0acd1e2f10daee9319a3f17f3fb792f9ebb1a Mon Sep 17 00:00:00 2001
From: Jon Snelling <jon.snelling@gmail.com>
Date: Mon, 26 Dec 2016 05:49:51 -0800
Subject: [PATCH] Preserve RECURSIVE flag of CTE relations when they are
 merged.

Queries like the following:
Tag.all.merge(Tag.with.recursive(recursive: Tag.where(tag: 'tag')))
Tag.with.recursive(recursive: Tag.where(tag: 'tag')).merge(Tag.all)

would both be expected to produce a query like:
WITH RECURSIVE "recursive"
   AS ( SELECT "tags".*
          FROM "tags"
         WHERE "tags"."tag" = 'tag')
SELECT "tags".*
  FROM "tags"

but currently only the second one would. The first would lose the recursive flag
during merge and result in:
WITH "recursive"
   AS ( SELECT "tags".*
          FROM "tags"
         WHERE "tags"."tag" = 'tag')
SELECT "tags".*
  FROM "tags"

Adding :recursive to ActiveRecord::Relation::Merger#normal_values
and a #recursive! method to ActiveRecord::QueryMethods the expected behavior
regardless of the direction of the merge.
---
 lib/postgres_ext/active_record/relation/merger.rb        | 2 +-
 lib/postgres_ext/active_record/relation/query_methods.rb | 5 +++++
 test/queries/common_table_expression_test.rb             | 8 ++++++++
 test/test_helper.rb                                      | 2 ++
 4 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/lib/postgres_ext/active_record/relation/merger.rb b/lib/postgres_ext/active_record/relation/merger.rb
index dca6b4e..da8163f 100644
--- a/lib/postgres_ext/active_record/relation/merger.rb
+++ b/lib/postgres_ext/active_record/relation/merger.rb
@@ -2,7 +2,7 @@ module ActiveRecord
   class Relation
     class Merger # :nodoc:
       def normal_values
-        NORMAL_VALUES + [:with]
+        NORMAL_VALUES + [:with, :recursive]
       end
     end
   end
diff --git a/lib/postgres_ext/active_record/relation/query_methods.rb b/lib/postgres_ext/active_record/relation/query_methods.rb
index fee3765..9ad16c4 100644
--- a/lib/postgres_ext/active_record/relation/query_methods.rb
+++ b/lib/postgres_ext/active_record/relation/query_methods.rb
@@ -201,6 +201,11 @@ def ranked!(value)
       self
     end
 
+    def recursive!(value)
+      self.recursive_value = value
+      self
+    end
+
     def build_arel_with_extensions
       arel = build_arel_without_extensions
 
diff --git a/test/queries/common_table_expression_test.rb b/test/queries/common_table_expression_test.rb
index 885c61d..c77a10a 100644
--- a/test/queries/common_table_expression_test.rb
+++ b/test/queries/common_table_expression_test.rb
@@ -22,6 +22,14 @@
       query.to_sql.must_match(/WITH RECURSIVE "lucky_number_seven" AS \(SELECT "people".* FROM "people"(\s+)WHERE "people"."lucky_number" = 7\) SELECT "people".* FROM "people" JOIN lucky_number_seven ON lucky_number_seven.id = people.id/)
     end
 
+    it 'preserves recursive expression during merges' do
+      merge_recursive_in   = Tag.all.merge(Tag.recursive)
+      merge_recursive_in.to_sql.must_match(/WITH RECURSIVE "recursive" AS \(SELECT "tags".* FROM "tags"(\s+)WHERE "tags"."tag" = 'tag'\) SELECT "tags".* FROM "tags"/)
+
+      merge_into_recursive = Tag.recursive.merge(Tag.all)
+      merge_into_recursive.to_sql.must_match(/WITH RECURSIVE "recursive" AS \(SELECT "tags".* FROM "tags"(\s+)WHERE "tags"."tag" = 'tag'\) SELECT "tags".* FROM "tags"/)
+    end
+
     it 'accepts Arel::SelectMangers' do
       arel_table = Arel::Table.new 'test'
       arel_manager = arel_table.project arel_table[:foo]
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 6c0105a..1ccc7e6 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -25,6 +25,8 @@ def self.wicked_people
 
 class Tag < ActiveRecord::Base
   belongs_to :person
+
+  scope :recursive, -> { with.recursive(recursive: Tag.where(tag: 'tag')) }
 end
 
 class ParentTag < Tag