Re: HOT patch - version 15

On Mon, 2007-09-10 at 12:17 +0100, Heikki Linnakangas wrote:
> Bruce Momjian wrote:
> > (Can someone time the access time for following a chain that fills an
> > entire page (the worst case) vs. having a single tuple on the page?)
>
> Here is some results, on my laptop.

>               HEAD    HOT     HOT-opt HOT-pruned
> seqscan               19.9    21.1    20.1    11.5
> idxscan               27.8    31.4    30.4     13.7
>

> Comparing the idxscan columns, it looks like following the chain *is*
> more expensive than having to go through killed index pointers. Pruning
> clearly does help.
>
> Given that this test is pretty much the worst case scenario, I'm ok with
> not pruning for the purpose of keeping chains short.

I wasn't expecting that result and had accepted the counter argument.