Re: simplehash: tb->sizemask = 0

On 11/29/17 13:49, Andres Freund wrote:
> On 2017-11-27 22:53:41 -0500, Tom Lane wrote:
>> Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
>>> I'm a bit puzzled by this code in SH_COMPUTE_PARAMETERS:
>>
>>>      if (tb->size == SH_MAX_SIZE)
>>>          tb->sizemask = 0;
>>>      else
>>>          tb->sizemask = tb->size - 1;
>>
>>> Doesn't that mean that with SH_MAX_SIZE we end up with sizemask being 0
>>> (i.e. no bits set)?
>>
>> Yeah, which is very obviously broken: for one thing, the Asserts
>> in SH_NEXT/SH_PREV would surely go off.
> 
> That's obviously wrong. Not sure how that happened. I might have had it
> as a shift at first?
> 
> 
>> (Why are those assertions, anyway, and not test-and-elog?
>> I do not think an assertion failure is a suitable way to
>> report "hash table full".)
> 
> There's a test and elog during insert. Adding actual branches into
> SH_NEXT/SH_PREV seems like a bad idea.
> 
> Will test a fix.

I'll be happy to help test this fix when it's ready.

-- todd