Infinite recursion detected... How do I prevent that?

[Alban Hertroys <alban@xxxxxxxxxxxxxxxxx>]

I have a rule similar to this:

CREATE RULE rule_branch_delete AS
ON DELETE TO tree
DO DELETE
     FROM tree
    WHERE ancestor_id IS NOT NULL
      AND OLD.child_id = ancestor_id;

The data is oraganized like this:

ancestor_id	child_id
================================
NULL		1
1		2
1		3
1		4
1		5
1		6
1		7
1		8
2		4
2		5
2		6
3		7
3		8
etc.

This is an optimization table that relates all nodes in a branch to all 
it's ancestor nodes; to it's parent, to it's grand parent to it's grand 
grand parent, etc.

The tree is 3 to 5 levels deep. The intention is to delete all children 
of a branch that share the same ancestor when an ancestor gets deleted. 
This happens recursively, of course.

If I try a delete on the tree table I get "Infinite recursion detected 
on rules on tree". I'm pretty sure it's not "infinite" in my case, how 
can I make it delete the records regardless this "infinity"?

At the moment I use a trigger, but I would prefer a rule.

Alban.

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