I usually tell people to use official MySQL builds from MySQL, or from their operating system distribution if they don’t want to do that. (This assumes that there is no compelling reason to use third-party builds such as Percona’s.) Sometimes, though, people want to create their own builds, or use a build that is “optimized” [...]
MySQL Limitations Part 3: Subqueries
October 25, 2010 By 21 Comments
This is the third in a series on what’s seriously limiting MySQL in certain circumstances (links: part 1, 2). This post is about subqueries, which in some cases execute outside-in instead of inside-out as users expect.
Performance Optimization and Six Sigma
June 7, 2010 By 6 Comments
You might be familiar with Six Sigma business management strategy which is employed by variety of the companies in relationship to managing quality of its product. Six Sigma applies to number of defects – when you have reached six sigma quality in your production you would see 99.99966% of the products manufactured with no defects, [...]
Is your server’s performance about to degrade?
May 18, 2010 By 13 Comments
I’ve been talking and writing a bit lately about the scaling problems I’m seeing on fast servers running lots of queries. As a rough guide, I’m seeing this in servers running 20k queries per second and higher, lots of memory, lots of CPU cores, and most queries are running faster than one millisecond; some in [...]
When the subselect runs faster
March 18, 2010 By 9 Comments
A few weeks ago, we had a query optimization request from one of our customer. The query was very simple like:
1 | SELECT * FROM `table` WHERE (col1='A'||col1='B') ORDER BY id DESC LIMIT 20 OFFSET 0 |
This column in the table is looks like this:
1 | `col1` enum('A','B','C','CD','DE','F','G','HI') default NULL |
The table have 549252 rows and of course, there is an index on the col1. MySQL estimated the cardinality of that index as [...]
A micro-benchmark of stored routines in MySQL
August 16, 2009 By 7 Comments
Ever wondered how fast stored routines are in MySQL? I just ran a quick micro-benchmark to compare the speed of a stored function against a “roughly equivalent” subquery. The idea — and there may be shortcomings that are poisoning the results here, your comments welcome — is to see how fast the SQL procedure code [...]
When would you use SAN with MySQL ?
March 9, 2009 By 18 Comments
One question which comes up very often is when one should use SAN with MySQL, which is especially popular among people got used to Oracle or other Enterprise database systems which are quite commonly deployed on SAN. My question in such case is always what exactly are you trying to get by using SAN ?
Beware: ext3 and sync-binlog do not play well together
January 21, 2009 By 19 Comments
One of our customers reported strange problem with MySQL having extremely poor performance when sync-binlog=1 is enabled, even though the system with RAID and BBU were expected to have much better performance. The problem could be repeated with SysBench as follows:
1 | ./sysbench --num-threads=2 --test=oltp --oltp-test-mode=complex --oltp-table-size=100000 --oltp-distinct-ranges=0 --oltp-order-ranges=0 --oltp-sum-ranges=0 --oltp-simple-ranges=0 --oltp-point-selects=0 --oltp-range-size=0 --mysql-table-engine=innodb --mysql-user=root --max-requests=0 --max-time=60 --mysql-db=test run |
Scaling to 256-way the Sun way
November 11, 2008 By 13 Comments
As you may have recently seen there are some articles about scaling MySQL one 256-way system. I though wow did they really make it work, considering how many bottlenecks remain in MySQL. What article really tells us ?
Poor man’s query logging
November 7, 2008 By 5 Comments
Occasionally there is a need to see what queries reach MySQL. The database provides several ways to share that information with you. One is called general log activated with
1 | --log |
(or
1 | --general-log |
in MySQL 5.1+) start-up parameter. The log writes any query being executed by MySQL to a file with limited amount of additional information. [...]
