InnoDB uses its own mutexes and read-write locks instead of POSIX-mutexes pthread_mutex*, the main reason for that is performance, but InnoDB’s implementation isn’t ideal and on modern SMP boxes can cause serious performance problems.
Let’s look on InnoDB mutex (schematic for simplification):
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Starting September I’m leaving MySQL to partner with Peter on practice as well as work with him on some Web projects.
I really enjoyed working under Peter’s guidance while working for MySQL and it is great we now can work together as a partners. I thanks MySQL for two great years I had.
I […]
(There is an updated version of this post here)
MySQL has useful extention to the GROUP BY operation: function GROUP_CONCAT:
GROUP_CONCAT(expr) – This function returns a string result with the concatenated non-NULL values from a group.
Where it can be useful?
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Today MySQL published the press release with results of Database Contest (results on German available here http://www.mysql.de/ct-dbcontest).
Peter and me spent quite some time working on this project while being employed by MySQL and it is great to see results finally publicly available.
The story began about year ago when C’T magazine had called for Database […]
Sysbench is benchmark developed by Alexey Kopytov (software engineer @ MySQL AB)
– http://sysbench.sourceforge.net/ and I want to write a short intro about this tool as sysbench is one of software for my everyday use. For example, SUN published their Solaris vs RedHat stuff based on sysbench’s results (Peter and me provided performance consutling for […]
I’m again returning to InnoDB scalability and related bug #15815 as it hurts many users and customers using multi-cpu servers.
Short intro into problem:
On 4-CPU box 1 thread executes full-table scan select query for 8 sec,
but with 4 threads – each thread executes query for 240 sec.
It is very strange as threads use only SELECT […]
We are going to release several patches which are not included in official MySQL releases.
First one is automatically stack trace for x86_64 systems. Currently MySQL resolves stack in crash only for x86 boxes.
You can download patch for 5.0.22 source tree here.
How to use: place stack64.diff into main source dir; execute patch -p1 < stack64.diff.
One [...]
Sometime it is needed to handle a lot of rows on client side. Usual way is send query via mysql_query and than handle the result in loop mysql_fetch_array (here I use PHP functions but they are common or similar for all APIs, including C).
Consider table:
Shell
CREATE TABLE `longf` (
`f1` int(11) NOT NULL auto_increment,
[…]
I’m continuing my experiments with different OS and today I tested FreeBSD 6.0 on my box.
(more details about box and benchmark see here https://www.percona.com/blog/2006/06/13/quick-look-at-ubuntu-606/).
Initially I was very pessimistic about FreeBSD, as results were (in transactions/sec, more is better.
for comparison the results from Suse 10.0):
InnoDB
threads
FreeBSD 6
Suse 10.0
Suse/ FreeBSD ratio
1
436.97
536.91
1.23
4
322.08
816.27
2.53
16
519.94
639.05
1.23
64
crash
547.07
256
357.09
MyISAM
threads
FreeBSD 6
Suse 10.0
Suse/ FreeBSD ratio
1
335.56
429.89
1.28
4
165.16
863.23
5.23
16
322.66
537.67
1.67
64
crash
516.00
256
346.65
The crash with […]
Read moreArjen posted a good note about MyISAM concurrent-insert features, though I should mention concurrent-insert can be cause of
scalablity and peformance problems on SMP boxes, especially on queries processing range-queries. The reason of problems is POSIX read-write locks, which are used to protect key_buffer from concurrent changes and called for each processed row. More info […]
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