On Tue, Sep 9, 2014 at 10:25 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Michael Paquier <michael(dot)paquier(at)gmail(dot)com> writes:
>> The logic for nested OR is correct by reading it, hence why not simply
>> removing the assertion failing? The attached patch 1 does so.
>
> The reason for the assert is that there should never be an OR directly
> underneath an OR in the planner after eval_const_expressions has flattened
> such cases. Evidently commit f343a88 failed to preserve AND/OR flatness
> in some cases :-(. That code should be taught to do so, rather than
> lobotomizing this assertion. Lack of flatness causes optimization
> inefficiencies, which is why we don't want to just allow it.
Ah, OK, I just saw your commit. so the trick is to add the arguments
of subclause in case of an OR clause found to have a correct
flattening here... Thanks!
--
Michael