From: | AP <ap(at)zip(dot)com(dot)au> |
---|---|
To: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: pgsql 10: hash indexes testing |
Date: | 2017-07-06 13:10:34 |
Message-ID: | 20170706131034.vgnkkc3pbg7ugujk@zip.com.au |
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Lists: | pgsql-hackers |
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(at)zip(dot)com(dot)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.
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