On 2018/08/09 13:00, Tom Lane wrote:
> Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> writes:
>> One reason why we should adapt such a test case is that, in the future, we
>> may arrange for make_partitionedrel_pruneinfo(), whose code we just fixed,
>> to not be called if we know that run-time pruning is not needed. It seems
>> that that's true for the test added by the commit, that is, it doesn't
>> need run-time pruning.
>
> Not following your argument here. Isn't make_partition_pruneinfo
> precisely what is in charge of figuring out whether run-time pruning
> is possible?
With the current coding, yes, it is...
> (See my point in the other thread about Jaime's assertion crash,
> that no run-time pruning actually would be possible for that query.
> But we got to the assertion failure anyway.)
The first time I'd seen that make_partition_pruneinfo *always* gets called
from create_append_plan if rel->baserestrictinfo is non-NIL, I had
wondered whether we couldn't avoid doing it for the cases for which we'll
end up throwing away all that work anyway. But looking at the code now,
it may be a bit hard -- analyze_partkey_exprs(), which determines whether
we'll need any execution-time pruning, could not be called any sooner.
So, okay, I have to admit that my quoted argument isn't that strong.
Thanks,
Amit