MySQL Bugs: #42483: innodb_buffer_pool_pages_latched status variable silently removed

Bug #42483	innodb_buffer_pool_pages_latched status variable silently removed
Submitted:	30 Jan 2009 14:46	Modified:	5 Feb 2009 20:31
Reporter:	Pierre Dumont	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S3 (Non-critical)
Version:	5.1.30/5.0	OS:	Linux
Assigned to:	Paul DuBois	CPU Architecture:	Any
Tags:	documentation, innodb

Description:
I hope this is the right place to post.

The innodb_buffer_pool_pages_latched status variable seems to have been silently removed from server version 5.1.30.
I understand the removal was triggered by performance considerations.
The problem is the documentation does not mention this removal.
The 5.0 manual states : "Added in MySQL 5.0.2."
The 5.1 manual contains the exact same definition without the last statement.

How to repeat:
Check it does exist on 5.0:

root@localhost((none)) >select version();
+-------------+
| version()   |
+-------------+
| 5.0.51a-log |
+-------------+
1 row in set (0.00 sec)

root@localhost((none)) >show status like 'innodb_buffer_pool_pages_latched';
+----------------------------------+-------+
| Variable_name                    | Value |
+----------------------------------+-------+
| Innodb_buffer_pool_pages_latched | 0     |
+----------------------------------+-------+
1 row in set (0.00 sec)

Check it does not exist anymore on 5.1.30:
root@localhost((none)) >select version();
+------------+
| version()  |
+------------+
| 5.1.30-log |
+------------+
1 row in set (0.00 sec)

root@localhost((none)) >show status like 'innodb_buffer_pool_pages_latched';
Empty set (0.00 sec)

Suggested fix:
Update the documentation.

It was removed from 5.0 in source server too:

C:\temp\mysql-5.0.67-win32>bin\mysql -uroot
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.0.67-community MySQL Community Edition (GPL)

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> show status like 'innodb_buffer_pool_pages_latched';
+----------------------------------+-------+
| Variable_name                    | Value |
+----------------------------------+-------+
| Innodb_buffer_pool_pages_latched | 0     |
+----------------------------------+-------+
1 row in set (0.02 sec)

c:\dbs>c:\dbs\5.0\bin\mysql -uroot --port=3500 --prompt="mysql 5.0 > "
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.0.76-nt-log Source distribution

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql 5.0 > show status like 'innodb_buffer_pool_pages_latched';
Empty set (0.05 sec)

Thank you for the bug report.

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.

Calculation of this variable is expensive, so as of MySQL 5.0.68, 5.1.28, 6.0.6, it is available only if the UNIV_DEBUG symbol is defined at server build time. (See Bug#36600)