Re: Bug? ExecChooseHashTableSize() got assertion failed with crazy number of rows

Kevin Grittner <kgrittn(at)ymail(dot)com> writes:
> Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> wrote:
>> we may need a couple of overhaul around HashJoin to support large
>> size of data, not only nbuckets around 0x80000000.

> Perhaps, but this is a clear bug, introduced to the 9.5 code, with
> an obvious fix; so I've pushed the change from 1 to 1L on that left
> shift.

I don't think it's anywhere near as clear as you think. The preceding
lines should have limited nbuckets to be no more than INT_MAX/2, so how
could an overflow occur there? (The result of 1<<mylog() should be
at most 0x40000000 AFAICS.) If overflow is possible, how will s/1/1L/
make it better on machines where int and long are the same size?

And on machines where long is wider than int, you've still got a bug
if the result of the left shift somehow overflowed an int, because
it's going to be assigned to nbuckets which is an int.

So I think the "1" coding was just fine in context. If there is an
overflow in ExecChooseHashTableSize, it's somewhere else.

regards, tom lane