Bug #48519 InnoDB does 8 random dives, not 10 AFAIK
Submitted: 3 Nov 2009 23:48 Modified: 7 Nov 2009 17:51
Reporter: Baron Schwartz (Basic Quality Contributor) Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server: Documentation Severity:S3 (Non-critical)
Version: OS:Any
Assigned to: Paul DuBois CPU Architecture:Any
Tags: qc

[3 Nov 2009 23:48] Baron Schwartz 
Description:
The manual says in http://dev.mysql.com/doc/refman/5.0/en/innodb-restrictions.html that InnoDB does 10 random dives (elsewhere "ten random dives" -- search the manual).  I believe from a little source inspection that it is 8, not ten, but I could be wrong.  Others appear to agree with me, ex: Vasil on http://bugs.mysql.com/bug.php?id=43660

How to repeat:
docs

Suggested fix:
docs
[4 Nov 2009 5:33] Valeriy Kravchuk 
Indeed, number of "dives" is defined in the source as follows:

btr/btr0cur.c:57:#define BTR_KEY_VAL_ESTIMATE_N_PAGES   8
[7 Nov 2009 17:51] Paul DuBois 
Thank you for your bug report. This issue has been addressed in the documentation. The updated documentation will appear on our website shortly, and will be included in the next release of the relevant products.

You're correct, it's 8, not 10.

Also, if you are using InnoDB Plugin (optional in 5.1.38 and up, default in 5.4.2 and up), the number of random dives can be changed by setting the  innodb_stats_sample_pages system variable. See:
http://www.innodb.com/doc/innodb_plugin-1.0/innodb-other-changes.html