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<chapter id="rules">

<title>The Rule System</title>

The query trees generated from rule actions are thrown into the

rewrite system again, and maybe more rules get applied resulting

in more or less query trees.

So the query trees in the rule actions must have either a different command type

or a different result relation, otherwise, this recursive process will end up in a loop.

There is a fixed recursion limit of currently 100 iterations.

If after 100 iterations there are still update rules to apply, the

rule system assumes a loop over multiple rule definitions and reports

an error.

So a rule's actions must have either a different

command type or a different result relation than the rule itself is

on, otherwise this recursive process will end up in an infinite loop.

(Recursive expansion of a rule will be detected and reported as an

error.)

</para>

<para>