Re: [Suspect SPAM] Re: [HACKERS] path toward faster partition pruning

Thank you Marina for the report and Michael for following up.

On 2018/05/07 16:56, Michael Paquier wrote:
> On Mon, May 07, 2018 at 10:37:10AM +0900, Michael Paquier wrote:
>> On Fri, May 04, 2018 at 12:32:23PM +0300, Marina Polyakova wrote:
>>> I got a similar server crash as in [1] on the master branch since the commit
>>> 9fdb675fc5d2de825414e05939727de8b120ae81 when the assertion fails because
>>> the second argument ScalarArrayOpExpr is not a Const or an ArrayExpr, but is
>>> an ArrayCoerceExpr (see [2]):
>>
>> Indeed, I can see the crash. I have been playing with this stuff and I
>> am in the middle of writing the patch, but let's track this properly for
>> now.
>
> So the problem appears when an expression needs to use
> COERCION_PATH_ARRAYCOERCE for a type coercion from one type to another,
> which requires an execution state to be able to build the list of
> elements. The clause matching happens at planning state, so while there
> are surely cases where this could be improved depending on the
> expression type, I propose to just discard all clauses which do not
> match OpExpr and ArrayExpr for now, as per the attached. It would be
> definitely a good practice to have a default code path returning
> PARTCLAUSE_UNSUPPORTED where the element list cannot be built.
>
> Thoughts?

I have to agree to go with this conservative approach for now. Although
we might be able to evaluate the array elements by applying the coercion
specified by ArrayCoerceExpr, let's save that as an improvement to be
pursued later.

FWIW, constraint exclusion wouldn't prune in this case either (that is, if
you try this example with PG 10 or using HEAD as of the parent of
9fdb675fc5), but it doesn't crash like the new pruning code does.

Thanks again.

Regards,
Amit