Recursive queries are typically used to deal with hierarchical or tree-structured data. In some conditions when data contain relationships with cycles recursive query will loop unlimited and significantly slows the client's session. To prevent "infinite" loop I suggest the max_recursion_depth parameter, which defines the maximum recursion level during the execution of recursive query. When max_recursion_depth > 0 and the recursion level of query exceeds specified value then the execution of query interrupts with error message. In the MS SQL Server there is MAXRECURSION hint for the same purpose.
