As you saw, I've not blogged for a long time on this site. I managed two different blogs for a while, but now it's the time to condense everything on one of it; and the winner is: It's Just About Communication.
I moved all the old posts, so that it becomes the unique source of informations about myself and my job. You can find a bunch of new articles on the sidebar, pointing to the aforementioned blog.
See you on the new home!
Q: What SQL is running on your MySQL database server now?
A: The bane of pain for MySQL DBA’s when there is no official
MySQL instrumentation that is dynamic and fine grained
sufficiently to solve this problem at the SQL interface.
While hybrid solutions exist, the lack of dynamic and real-time are the issues. There is however great work being done by Baron and others on Maatkit mk-query-digest and packet sniffing the MySQL TCP packets.
$ sudo tcpdump -i eth0 port 3306 -s 65535 -x -n -q -tttt | ./mk-query-digest --type tcpdump tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes # Caught SIGINT. 5444 packets captured 8254 packets received by filter 2809 packets dropped by kernel # 2.1s user time, 40ms system time, 22.23M rss, 57.60M vsz # …[Read more]
As you saw, I've not blogged for a long time on this site. I managed two different blogs for a while, but now it's the time to condense everything on one of it; and the winner is: It's Just About Communication.
I moved all the old posts, so that it becomes the unique source of informations about myself and my job. You can find a bunch of new articles on the sidebar, pointing to the aforementioned blog.
See you on the new home!
As you saw, I've not blogged for a long time on this site. I managed two different blogs for a while, but now it's the time to condense everything on one of it; and the winner is: It's Just About Communication.
I moved all the old posts, so that it becomes the unique source of informations about myself and my job. You can find a bunch of new articles on the sidebar, pointing to the aforementioned blog.
See you on the new home!
If you’ve ever done any non-blocking programming (usually for socket I/O), you’ve probably had to come up with a non-trivial state machine to handle all the places where everything can pause. Say you’re reading an application level packet from a socket, and half way through the read() system call it screams EAGAIN. You need to stop, save any state, and exit out of whatever chain of functions got you there so the calling application can regain control. I’m going to explain a few techniques I’ve come up with over the years, each with their strengths and weaknesses, and I hope this will spur some conversation of what other folks have done. While I’m fairly happy with how I handle these state machines now, but I’m always looking for a more succinct way of handling things. Please share your thoughts!
Switch Statements
The obvious way to handle non-blocking I/O is with one or more switch statements. Say we need to …
[Read more]The past week has brought a surge of Gearman related releases. They include:
C Server
and Library
Perl Server and Modules
Gearman::XS Perl Module (based on C library)
PHP
Extension (based on C library)
PHP Extension Documentation
Drizzle
UDFs
PostgreSQL UDFs
MySQL UDFs
Some of …
[Read more]Answering questions asked on the site.
Princess asks:
Hello, I’ve got a problem with SQL.
I have a table which contains the production details for the factories. They are not factories and items of course but I cannot disclose the project and need to obfuscate so let’s pretend they are :)
I need to select the items for which the first 5 factories have low production rate.
I tried to do the query like this:
SELECT ProductionItem
FROM FactoryProductions
WHERE 5 >= FactoryID
AND 100 >= ProductionAmount
which returns correct results but is slow.
I have an index on (FactoryID, ProductionAmount).
There are 13 Factories and 2,300,000 Items
This is in MySQL
This is a nice illustration of how index range evaluation works …
[Read more]There are many areas you need to review when addressing MySQL performance such as current database load, executed SQL statements, connections, configuration parameters, memory usage, disk to memory ratio, hardware performance & bottlenecks just to name a few.
If you were to just look at the data that is held in the
database, what would you consider?
Here are my tips, when looking just at the data.
If you need an ad-hoc Query Tool for MySQL on Windows, then
MyQuery might be what you aere looking for. MyQuery is an Open
Source, free Windows tool, supporting colour syntax
highlightning, multi-tab editing, several information, status and
dictionary features and much more.
The latest release is MyQuery 3.2.1, and if you have followed the
development of MyQuery, you know that the 3.x releases are
focused on features and usability, and 3.2.1 has advances in both
areas:
This is a hack, but it is a good one. I was looking at some machines on a new client, and they had the general log turned on. I was surprised, because it was a fairly busy server, and they had had many problems with the server a few months ago. I thought perhaps they had turned on the general log to diagnose a problem and forgotten to turn it off, or something similar.
When I looked at the log on disk, I saw it was a symlink to /dev/null. They were running MySQL 5.0, so I immediately realized that it was a hack to have a general log they could “turn on” without having to restart mysqld.
On a different server, I saw the same link to /dev/null done with a slow query log.
The drawbacks to doing it this way is that MySQL still has the overhead of writing to the log file. The I/O overhead is greatly reduced because the writes are to /dev/null, but there’s still overhead from other resources such as RAM, CPU, etc.
…
[Read more]