| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Josh Berkus <josh(at)agliodbs(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Bug? Small samples in TABLESAMPLE SYSTEM returns zero rows |
| Date: | 2015-08-06 19:27:02 |
| Message-ID: | CANP8+j+R8pmBNKO8DJLf5+m5ezVrh9xTF_BaXZhLPPTHVOC=iA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 6 August 2015 at 20:14, Josh Berkus <josh(at)agliodbs(dot)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 of the % requested by the user, and which includes 0.
>
Thanks for the report, I'll look at this now.
> 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 possible to return zero
> rows from a populated table.
>
Please bear in mind you have requested a very small random sample of blocks.
--
Simon Riggs http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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