(2010/07/20 2:13), Heikki Linnakangas wrote:
> On 09/07/10 06:47, KaiGai Kohei wrote:
>> When leaky and non-leaky functions are chained within a WHERE clause,
>> it will be ordered by the cost of functions. So, we have possibility
>> that leaky functions are executed earlier than non-leaky functions.
>
> No, that needs to be forbidden as part of the fix. Leaky functions must
> not be executed before all the quals from the view are evaluated.
>
IIUC, a view is extracted to a subquery in the rewriter phase, then it
can be pulled up to join clause at pull_up_subqueries(). In this case,
WHERE clause may have the quals come from different origins, isn't it?
E.g)
SELECT * FROM v1 WHERE f_malicious(v1.a);
At the rewriter:
-> SELECT v1.* FROM (SELECT * FROM t1 WHERE f_policy(t1.b)) v1 WHERE
f_malicious(v1.a);
At the pull_up_subqueries()
-> SELECT * FROM t1 WHERE f_policy(t1.b) AND f_malicious(t1.a);
^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^
cost = 100 cost = 0.0001
Apart from an idea of secure/leaky function mark, isn't it necessary any
mechanism to enforce f_policy() shall be executed earlier than f_malicious()?
Thanks,
--
KaiGai Kohei <kai...@ak.jp.nec.com>
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