MySQL Forums
Forum List  »  Optimizer & Parser

Statistics used by optimizer.
Posted by: Rakshit Trivedi
Date: August 28, 2009 07:32AM

Hi,

I wanted to know about the use of statistics by MYSQL optimizer. According to what I have followed, for estimating the number of rows to be read from a table , the optimizer probes the indexes and calculates the values. Is it true that for different constant values for a given query, the optimizer probes and accesses the indexes to estimate the rows? Or does it only use the already stored statistics of the table?

And one more question. While browsing on summaries and statistics used by MYSQL, I came across the following post:
http://forge.mysql.com/worklog/task.php?id=4816

Here, the reasons for not preferring the histograms are presented. I just wanted to know how the use of histograms leads the optimizer not to use right instructions mentioned there? And how not using histograms is beneficial to optimizer?

Thanks.

Options: ReplyQuote


Subject
Views
Written By
Posted
Statistics used by optimizer.
5557
August 28, 2009 07:32AM
2345
August 29, 2009 01:11PM
2183
September 01, 2009 06:30AM
2085
September 01, 2009 07:44AM
2171
September 01, 2009 02:51PM
2028
September 01, 2009 09:59PM
2094
September 04, 2009 11:00AM
2151
September 04, 2009 07:37PM


Sorry, you can't reply to this topic. It has been closed.

Content reproduced on this site is the property of the respective copyright holders. It is not reviewed in advance by Oracle and does not necessarily represent the opinion of Oracle or any other party.