1 files changed, 99 insertions, 0 deletions
diff --git a/activerecord/test/cases/arel/visitors/mssql_test.rb b/activerecord/test/cases/arel/visitors/mssql_test.rb
new file mode 100644
index 0000000000..340376c3d6
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/mssql_test.rb
@@ -0,0 +1,99 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Visitors
+    class MssqlTest < Arel::Spec
+      before do
+        @visitor = MSSQL.new Table.engine.connection
+        @table = Arel::Table.new "users"
+      end
+
+      def compile(node)
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      it "should not modify query if no offset or limit" do
+        stmt = Nodes::SelectStatement.new
+        sql = compile(stmt)
+        sql.must_be_like "SELECT"
+      end
+
+      it "should go over table PK if no .order() or .group()" do
+        stmt = Nodes::SelectStatement.new
+        stmt.cores.first.from = @table
+        stmt.limit = Nodes::Limit.new(10)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY \"users\".\"id\") as _row_num FROM \"users\") as _t WHERE _row_num BETWEEN 1 AND 10"
+      end
+
+      it "caches the PK lookup for order" do
+        connection = Minitest::Mock.new
+        connection.expect(:primary_key, ["id"], ["users"])
+
+        # We don't care how many times these methods are called
+        def connection.quote_table_name(*); ""; end
+        def connection.quote_column_name(*); ""; end
+
+        @visitor = MSSQL.new(connection)
+        stmt = Nodes::SelectStatement.new
+        stmt.cores.first.from = @table
+        stmt.limit = Nodes::Limit.new(10)
+
+        compile(stmt)
+        compile(stmt)
+
+        connection.verify
+      end
+
+      it "should use TOP for limited deletes" do
+        stmt = Nodes::DeleteStatement.new
+        stmt.relation = @table
+        stmt.limit = Nodes::Limit.new(10)
+        sql = compile(stmt)
+
+        sql.must_be_like "DELETE TOP (10) FROM \"users\""
+      end
+
+      it "should go over query ORDER BY if .order()" do
+        stmt = Nodes::SelectStatement.new
+        stmt.limit = Nodes::Limit.new(10)
+        stmt.orders << Nodes::SqlLiteral.new("order_by")
+        sql = compile(stmt)
+        sql.must_be_like "SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY order_by) as _row_num) as _t WHERE _row_num BETWEEN 1 AND 10"
+      end
+
+      it "should go over query GROUP BY if no .order() and there is .group()" do
+        stmt = Nodes::SelectStatement.new
+        stmt.cores.first.groups << Nodes::SqlLiteral.new("group_by")
+        stmt.limit = Nodes::Limit.new(10)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY group_by) as _row_num GROUP BY group_by) as _t WHERE _row_num BETWEEN 1 AND 10"
+      end
+
+      it "should use BETWEEN if both .limit() and .offset" do
+        stmt = Nodes::SelectStatement.new
+        stmt.limit = Nodes::Limit.new(10)
+        stmt.offset = Nodes::Offset.new(20)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY ) as _row_num) as _t WHERE _row_num BETWEEN 21 AND 30"
+      end
+
+      it "should use >= if only .offset" do
+        stmt = Nodes::SelectStatement.new
+        stmt.offset = Nodes::Offset.new(20)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY ) as _row_num) as _t WHERE _row_num >= 21"
+      end
+
+      it "should generate subquery for .count" do
+        stmt = Nodes::SelectStatement.new
+        stmt.limit = Nodes::Limit.new(10)
+        stmt.cores.first.projections << Nodes::Count.new("*")
+        sql = compile(stmt)
+        sql.must_be_like "SELECT COUNT(1) as count_id FROM (SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY ) as _row_num) as _t WHERE _row_num BETWEEN 1 AND 10) AS subquery"
+      end
+    end
+  end
+end