Re: GiST buffering build, bug in levelStep calculation

On Tue, May 29, 2012 at 11:42 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> While I'm looking at this, is the first test involving
> effective_cache_size bulletproof either? In particular, is
> avgIndexTuplesPerPage clamped to be strictly greater than 1?
>

It's based on collected statistics on already inserted tuple sizes. Since
tuple sizes are measured after possible toasting, I don't see the way
for avgIndexTuplesPerPage to be less than 1.

> And for that matter, is either test sane from a units standpoint?
> It seems to me that maxIndexTuplesPerPage would have units of
> 1/blocks, which is pretty dubious to be comparing to a block count
> even disregarding the power function.
>

In this test we use avgIndexTuplesPerPage as estimate for number of child
index pages of one page. I think we can assume it to have blocks unit.

------
With best regards,
Alexander Korotkov.