2015-10-28 14:33 GMT+01:00 Tom Lane <t...@sss.pgh.pa.us>: > Valery Popov <v.po...@postgrespro.ru> writes: > > 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. > > The standard way of dealing with that is to include logic in the query to > limit the recursion depth, for example > > WITH RECURSIVE t(n) AS ( > SELECT 1 > UNION ALL > SELECT n+1 FROM t WHERE n < 10 > ) > SELECT n FROM t; > > I don't see an example of this technique in the documentation, which maybe > is a documentation improvement opportunity. > > > To prevent "infinite" loop I suggest the max_recursion_depth parameter, > > which defines the maximum recursion level during the execution of > recursive > > query. > > Controlling this via a GUC is a seriously awful idea. We learned a long > time ago to avoid GUCs that have a direct impact on query semantics; the > scope of their effects is just about never what you want. > > Also, there are already ways to constrain queries-gone-crazy; particularly > statement_timeout, which has the advantage that it works for other types > of badly-written queries not only this one. >
isn't the recursive limits much more a resource limit like work_mem etc? Regards Pavel > > regards, tom lane > > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers >
