Databases Reference
In-Depth Information
In addition to these tables, MySQL 5.5 adds
INNODB_LOCK_WAITS
, which can help diag-
nose more types of lock-waiting problems more easily. MySQL 5.6 will add tables that
show more information about InnoDB's internals, including the buffer pool and data
dictionary, and a new table called
INNODB_METRICS
, which will be an alternative to using
the Performance Schema.
Tables in Percona Server
Percona Server adds a large number of tables to the
INFORMATION_SCHEMA
database. The
stock MySQL 5.5 server has 39 tables, and Percona Server 5.5 has 61 tables. Here's an
overview of the additional tables:
The “user statistics” tables
These tables originated in Google's patches for MySQL. They show activity sta-
tistics for clients, indexes, tables, threads, and users. We've mentioned uses for
these throughout this topic, such as determining when replication is beginning to
approach the limit of its ability to keep up with the master.
The InnoDB data dictionary
A series of tables that expose InnoDB's internal data dictionary as read-only tables:
columns, foreign keys, indexes, statistics, and so on. These are very helpful for
examining and understanding InnoDB's view of the database, which can differ
from MySQL's due to MySQL's reliance on
.frm
files to store the data dictionary.
Similar tables will be included with MySQL 5.6 when it is released.
The InnoDB buffer pool
These tables let you query the buffer pool as though it's a table where each page is
a row, so you can see what pages are resident in the buffer pool, what types of pages
they are, and so on. These tables have proven useful for diagnosing problems such
as a bloated insert buffer.
Temporary tables
These tables show the same type of information available in the
INFORMATION
_SCHEMA.TABLES
table, but for temporary tables instead. There is one for your own
session's temporary tables, and one for all temporary tables in the whole server.
Both are helpful for gaining visibility into which temporary tables exist, for which
sessions, and how much space they're using.
Miscellaneous tables
There are a handful of other tables that add visibility into query execution times,
files, tablespaces, and more InnoDB internals.
The documentation for Percona Server's additional tables is available at
http://www
