ADMIN

FeAtures
mysQL Forks and Patches
complete list of patches and notes on
how to use them.
© Dmitry Karasew, 123RF.com
Modern MySQL Forks and Patches
Spoiled for
Choice
mysQL is the standard solution for free relational database systems in web applications,
but new forks, more storage engines, and patched versions muddy the water.
now’s the time to take stock of the most important offerings. By caspar clemens mierau
If your MySQL server is too slow,
you have various approaches to solving
the problem. Besides optimizing
queries and indexes, reworking the
configuration, and upgrading your
hardware, moving to a customized
version of the MySQL server can be
a good idea. In recent years, so many
patches, forks, and new storage engines
have been released that it is
hard to keep track of them. For hardworking
developers and database
administrators, this means a change
from the simple choice of a standard
MySQL distribution.
Little Band-aids
Many enhancements for MySQL come
from major corporations like Facebook
[1] and Google [2], who run
their ad services on top of MySQL
or from MySQL specialists like Per-
cona [3], whose claim to fame is
the “MySQL Performance Blog” [4]
(standard reading for anyone interested
in MySQL). The patches can be
grouped into three categories: (1) reporting
enhancements, (2) functional
enhancements of the MySQL kernel
and database engines, and (3) performance
optimizations. In most cases, a
combination of patches from all three
categories will make the most sense.
Moving to a database server that you
patched and compiled yourself can
be a daunting prospect. Thankfully,
projects such as OurDelta [5] offer repositories
with meaningfully patched
and prebuilt MySQL packages for
popular distributions like Debian,
Ubuntu, and CentOS/ RHEL. The
patches I will be looking at in the rest
of this article are a cross-section of
the current OurDelta versions of the
MySQL server; see their website for a
Reporting
Extended reporting allows administrators
to collect more granular information
about the MySQL server’s
behavior under load. Thus far, slow.
log, which offers very little in the
line of configuration options, might
be your first port of call. However, its
utility value is restricted to identifying
individual, computationally intensive
queries on the basis of the time they
use – and non-used indexes. The
MicroSlow patch offers new filters
for a more targeted search for poorly
formulated queries. Thus, it logs queries
that are responsible for writing
temporary tables to disk, performing
complete table scans, or reading a
freely defined minimum number of
lines in a table. The mysqldumpslow
Slow.log statistics tool, which is not
very well known but is part of the
MySQL standard distribution, has
been modified to be able to read and
evaluate the extended entries.
Aggregated run-time statistics on usage
behavior are equally as useful.
The UserStats patch extends MySQL
by adding statistics for users, clients,
tables, and indexes. After enabling
data collection in my.cnf or issuing
the SQL SET GLOBAL userstat_running
= 1 command at run time, four tables
in the information_schema, USER_STA‐
TISTICS, CLIENT_STATISTICS, INDEX_
STATISTICS, and TABLE_STATISTICS,
are continually populated with data.
The statistics can be accessed via the
SHOW command. For example, SHOW
TABLE_STATISTICS will give you a
table-by-table evaluation of lines read
and modified and indexes updated.
Direct access to the statistics tables in
information_schema is useful because
they are accessed as normal tables,
and you can target the results to
manipulate. Listing 1 shows a query
for the five tables with the most
frequently read lines. This example
taken from Live operations of the
Rails-based Moviepilot movie community
and the underlying movie database
OMDB (both anonymized for
20 Admin 01 www.Admin-mAgAzine.com