Re: Hash Based Column Sampling In 11g As Compared To RowBased....
Date: Fri, 19 Dec 2008 05:57:10 -0800 (PST)
Message-ID: <2f38d751-4c59-4199-827b-495e62f205b4@g39g2000pri.googlegroups.com>
On Dec 19, 2:49 pm, Aman Sharma <amansharma1..._at_gmail.com> wrote:
> Hi,
> In 11g (11106), here is what is mentioned about the stats gathering,http://download.oracle.com/docs/cd/B28359_01/server.111/b28274/stats....
> In the 11g NF guide from OU, it is mentioned that prior to 11g , the
> column sampling was done with the help of "Row Based Sampling". In
> 11g, if one uses, ESTIMATE_PERCENT=>AUTO_SAMPLE_SIZE than the sampling
> technique is Hash Based. This is by default there from 11g onwards.
> Here are my questions,
> 1)What is the older Row Based Sampling and how it works?
> 2) What is the new Hash Based Sampling and how it works?
> 3) What's the benefit of the new technique?
> Thanks in advance.
> Aman....
This Oracle white paper might give a clue: http://www.oracle.com/technology/products/bi/db/11g/pdf/twp_bidw_dss_perf_11gr1.pdf
Regards,
Vladimir M. Zakharychev
N-Networks, makers of Dynamic PSP(tm)
http://www.dynamicpsp.com
Received on Fri Dec 19 2008 - 07:57:10 CST