Re: [HACKERS] pgsql 10: hash indexes testing

On Wed, Jul 05, 2017 at 07:31:39PM +1000, AP wrote:
> On Tue, Jul 04, 2017 at 08:23:20PM -0700, Jeff Janes wrote:
> > On Tue, Jul 4, 2017 at 3:57 AM, AP <ap@zip.com.au> wrote:
> > > The data being indexed is BYTEA, (quasi)random and 64 bytes in size.
> > > The table has over 2 billion entries. The data is not unique. There's
> > > an average of 10 duplicates for every unique value.
> > 
> > What is the number of duplicates for the most common value?
> 
> Damn. Was going to collect this info as I was doing a fresh upload but
> it fell through the cracks of my mind. It'll probably take at least
> half a day to collect (a simple count(*) on the table takes 1.5-1.75
> hours parallelised across 11 processes) so I'll probably have this in
> around 24 hours if all goes well. (and I don't stuff up the SQL :) )

Well...
num_ids |  count   
---------+----------      1 | 91456442      2 | 56224976      4 | 14403515     16 | 13665967      3 | 12929363     17 |
12093367    15 | 10347006
 


So the most common is a unique value, then a dupe.

AP.