Deveel.Data.Sql.Query.QueryTablePlanner.AssertBeNaturalJoin C# (CSharp) Method

        private static int AssertBeNaturalJoin(TablePlan plan1, TablePlan plan2)
        {
            if (plan1.LeftPlan == plan2 || plan1.RightPlan == plan2)
                return 0;
            if (plan1.LeftPlan != null && plan2.LeftPlan != null)
                // This is a left clash
                return 2;
            if (plan1.RightPlan != null && plan2.RightPlan != null)
                // This is a right clash
                return 1;
            if ((plan1.LeftPlan == null && plan2.RightPlan == null) ||
                (plan1.RightPlan == null && plan2.LeftPlan == null))
                // This means a merge between the plans is fine
                return 0;

            // Must be a left and right clash
            return 2;
        }