Petr,
Just user-tested SYSTEM_ROWS and SYSTEM_TIME. They work as expected.
Useful!
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Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com
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On 08/06/2015 01:10 PM, Simon Riggs wrote:
Given, user-stated probability of accessing a block of P and N total
blocks, there are a few ways to implement block sampling.
1. Test P for each block individually. This gives a range of possible
results, with 0 blocks being possible outcome,
Petr Jelinek wrote:
On 2015-08-06 22:25, Josh Berkus wrote:
If there is no appropriate place, I'll just write a blog.
There is a blog post on 2ndQ blog page which tries to describe the sampling
methods visually, not sure if it's more obvious from that or not. It's
somewhat broken on planet
On 6 August 2015 at 20:14, Josh Berkus j...@agliodbs.com wrote:
This table has around 185 rows per page. As the sample size goes up,
the number times I get zero rows goes down, but those results seem to
still include data pages with zero rows. For example, here's a series
of results from a
On 08/06/2015 01:14 PM, Josh Berkus wrote:
On 08/06/2015 01:10 PM, Simon Riggs wrote:
Given, user-stated probability of accessing a block of P and N total
blocks, there are a few ways to implement block sampling.
1. Test P for each block individually. This gives a range of possible
results,
On 6 August 2015 at 21:14, Josh Berkus j...@agliodbs.com wrote:
On 08/06/2015 01:10 PM, Simon Riggs wrote:
Given, user-stated probability of accessing a block of P and N total
blocks, there are a few ways to implement block sampling.
1. Test P for each block individually. This gives a
On 2015-08-06 22:25, Josh Berkus wrote:
On 08/06/2015 01:19 PM, Simon Riggs wrote:
For me, the docs seem exactly correct. The mathematical implications of
that just aren't recorded explicitly.
Well, for the SELECT page, all we need is the following (one changed
sentence):
The SYSTEM method
On 08/06/2015 12:45 PM, Tom Lane wrote:
Simon Riggs si...@2ndquadrant.com writes:
On 6 August 2015 at 20:14, Josh Berkus j...@agliodbs.com wrote:
Speaking from a user perspective, SYSTEM seems broken to me. I can't
imagine using it for anything with a that degree of variation in the
number
Simon Riggs si...@2ndquadrant.com writes:
On 6 August 2015 at 20:14, Josh Berkus j...@agliodbs.com wrote:
Speaking from a user perspective, SYSTEM seems broken to me. I can't
imagine using it for anything with a that degree of variation in the
number of results returned, especially if it's
On 2015-08-06 22:17, Josh Berkus wrote:
On 08/06/2015 01:14 PM, Josh Berkus wrote:
On 08/06/2015 01:10 PM, Simon Riggs wrote:
Given, user-stated probability of accessing a block of P and N total
blocks, there are a few ways to implement block sampling.
1. Test P for each block individually.
On 08/06/2015 01:19 PM, Simon Riggs wrote:
On 6 August 2015 at 21:14, Josh Berkus j...@agliodbs.com
mailto:j...@agliodbs.com wrote:
On 08/06/2015 01:10 PM, Simon Riggs wrote:
Given, user-stated probability of accessing a block of P and N total
blocks, there are a few ways to
On 6 August 2015 at 20:14, Josh Berkus j...@agliodbs.com wrote:
The results of 0, 185 and 925 are not. It really seems like SYSTEM is
treating 0.04% as a maximum, but taking a random number of data pages
somewhere around that maximum, using math which can choose numbers of
pages far outside
Version: 9.5alpha2
Issue: when requesting small samples, SYSTEM often returns zero rows,
and sometimes returns unexpected numbers of rows.
Example:
create table thous ( id int, val text );
insert into thous select i, i::text || '-val' from
generate_series(1,10) as gs(i);
analyze;
This is
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