Re: Declarative partitioning - another take

On Fri, Nov 25, 2016 at 5:49 AM, Amit Langote
<Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> 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.

> 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.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company