Amount of open cursor problem

Question

I am trying to display a tree-like data with a varchar2 field called ancestor indicating its family nodes, e.g. 1:2:5:16. A quick solution would be recurssion:
procedure data_list(id in number default null) as
cursor c1 is select * from table1 where ancestor is null;
cursor c2 is select * from table2 where get_parent(ancestor) = id;
-- get_parent(varchar2) is a function return parent id of current data.
if (id is null) then
-- display root nodes
-- open c1 and print out data
-- then recursively call itself to print out its children
data_list(id);
close c1;
else
-- open c2 and print out data
-- then recursively call itself to print out its childen
data_list(id);
close c2;
end if;
end data_list;
======================
As you notice, the problem is that if the tree is too high (or too deep) the amount of cursors being open simultanously might be huge, which will definitely degrade the performance of the server, especially under multiuser environment.
Does someone here have better solution for this problem?
Thanks.

Answer 1

You probably want to start by looking into Oracle's hierarchal query support with the CONNECT BY clause and the SYS_CONNECT_BY_PATH function. Grabbing a quick example from the Oracle SQL Reference http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96540/functions121a.htm#1038139
SELECT LPAD(' ', 2*level-1)||SYS_CONNECT_BY_PATH(last_name, '/') "Path"
   FROM employees
   START WITH last_name = 'Kochhar'
   CONNECT BY PRIOR employee_id = manager_id;
Path
/Kochhar
   /Kochhar/Greenberg
     /Kochhar/Greenberg/Faviet
     /Kochhar/Greenberg/Chen
     /Kochhar/Greenberg/Sciarra
     /Kochhar/Greenberg/Urman
     /Kochhar/Greenberg/Popp
   /Kochhar/Whalen
   /Kochhar/Mavris
   /Kochhar/Baer
   /Kochhar/Higgins
     /Kochhar/Higgins/GietzNote that hierarchal queries work very well when you have tree data. If you actually have a graph, it starts to get more complicated.
Justin
Distributed Database Consulting, Inc.
http://www.ddbcinc.com/askDDBC