Re: Declarative partitioning - another take

On Thu, Dec 1, 2016 at 12:48 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Fri, Nov 25, 2016 at 5:49 AM, Amit Langote wrote:
>> On 2016/11/25 11:44, Robert Haas wrote:
>>> On Thu, Nov 24, 2016 at 6:13 AM, Amit Langote wrote:
>>>> Also, it does nothing to help the undesirable situation that one can
>>>> insert a row with a null partition key (expression) into any of the range
>>>> partitions if targeted directly, because of how ExecQual() handles
>>>> nullable constraint expressions (treats null value as satisfying the
>>>> partition constraint).
>>>
>>> That's going to have to be fixed somehow. How bad would it be if we
>>> passed ExecQual's third argument as false for partition constraints?
>>> Or else you could generate the actual constraint as expr IS NOT NULL
>>> AND expr >= lb AND expr < ub.
>>
>> About the former, I think that might work. If a column is NULL, it would
>> be caught in ExecConstraints() even before ExecQual() is called, because
>> of the NOT NULL constraint. If an expression is NULL, or for some reason,
>> the partitioning operator (=, >=, or <) returned NULL even for a non-NULL
>> column or expression, then ExecQual() would fail if we passed false for
>> resultForNull. Not sure if that would be violating the SQL specification
>> though.
>
> I don't think the SQL specification can have anything to say about an
> implicit constraint generated as an implementation detail of our
> partitioning implementation.

Yeah, I thought so too.

>> The latter would work too. But I guess we would only emit expr IS NOT
>> NULL, not column IS NOT NULL, because columns are covered by NOT NULL
>> constraints.
>
> Right.

The latest patch I posted earlier today has this implementation.

Thanks,
Amit