Re: [WIP] Effective storage of duplicates in B-tree index.

On 28 January 2016 at 17:09, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> On Thu, Jan 28, 2016 at 9:03 AM, Thom Brown <thom(at)linux(dot)com> wrote:
>> I'm surprised that efficiencies can't be realised beyond this point. Your results show a sweet spot at around 1000 / 10000000, with it getting slightly worse beyond that. I kind of expected a lot of efficiency where all the values are the same, but perhaps that's due to my lack of understanding regarding the way they're being stored.
>
> I think that you'd need an I/O bound workload to see significant
> benefits. That seems unsurprising. I believe that random I/O from
> index writes is a big problem for us.

I was thinking more from the point of view of the index size. An
index containing 10 million duplicate values is around 40% of the size
of an index with 10 million unique values.

Thom