Add Gitlab::SQL:CTE for easily building CTE statements

1 files changed, 42 insertions, 0 deletions

diff --git a/spec/lib/gitlab/sql/cte_spec.rb b/spec/lib/gitlab/sql/cte_spec.rb
new file mode 100644
index 00000000000..d6763c7b2e1
--- /dev/null
+++ b/spec/lib/gitlab/sql/cte_spec.rb
@@ -0,0 +1,42 @@
+require 'spec_helper'
+
+describe Gitlab::SQL::CTE, :postgresql do
+  describe '#to_arel' do
+    it 'generates an Arel relation for the CTE body' do
+      relation = User.where(id: 1)
+      cte = described_class.new(:cte_name, relation)
+      sql = cte.to_arel.to_sql
+      name = ActiveRecord::Base.connection.quote_table_name(:cte_name)
+
+      sql1 = ActiveRecord::Base.connection.unprepared_statement do
+        relation.except(:order).to_sql
+      end
+
+      expect(sql).to eq("#{name} AS (#{sql1})")
+    end
+  end
+
+  describe '#alias_to' do
+    it 'returns an alias for the CTE' do
+      cte = described_class.new(:cte_name, nil)
+      table = Arel::Table.new(:kittens)
+
+      source_name = ActiveRecord::Base.connection.quote_table_name(:cte_name)
+      alias_name = ActiveRecord::Base.connection.quote_table_name(:kittens)
+
+      expect(cte.alias_to(table).to_sql).to eq("#{source_name} AS #{alias_name}")
+    end
+  end
+
+  describe '#apply_to' do
+    it 'applies a CTE to an ActiveRecord::Relation' do
+      user = create(:user)
+      cte = described_class.new(:cte_name, User.where(id: user.id))
+
+      relation = cte.apply_to(User.all)
+
+      expect(relation.to_sql).to match(/WITH .+cte_name/)
+      expect(relation.to_a).to eq(User.where(id: user.id).to_a)
+    end
+  end
+end