Re: hash index improving v3

"Alex Hunsaker" <badalex(at)gmail(dot)com> writes:
> On Thu, Sep 4, 2008 at 7:45 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> So what we need for testing is a few different key values that hash to
>> the same code. Not sure about an easy way to find such.

> Hrm, well I have not really looked at the hash algorithm but I assume
> we could just reduce the number of buckets?

No, we need fully equal hash keys, else the code won't visit the heap.

I guess one thing we could do for testing purposes is lobotomize one of
the datatype-specific hash functions. For instance, make int8_hash
return the input mod 2^32, ignoring the upper bytes. Then it'd be easy
to compute different int8s that hash to the same thing.

regards, tom lane