Ok, so I knew about innodb_table_monitor and innodb_tablespace_monitor. I’ve tried them before, looked at the output and given up, partly because it didn’t serve the purpose I wanted it to at the time, and also because it’s format was a little cryptic.

What I didn’t know was there are actually 4 monitors via this “create table functionality”. You can also do innodb_monitor which is the same as SHOW INNODB STATUS, and you can also do innodb_lock_monitor .

Another thing I didn’t know is that these commands don’t send the output just once, it’s on a timer. I’ve found the timers to be different. For innodb_monitor you get every 15 sec, as well as a nice line given time of averages which seems to always say 16 seconds.

=====================================
070601 15:11:25 INNODB MONITOR OUTPUT
=====================================
Per …

I've been looking through the Fedora Core 7 release notes this morning. One thing which stood out was their inclusion of Smolt.

Smolt is a hardware profiler which sends out put back to a public webserver being run by Redhat. Turn it on, and Redhat can see what hardware you are running. This type of phone home service is one that we have talked about for a long time at MySQL.

Would users be open to us sending back non private data about their systems? OS, machine type, config parameters, storage engines used... information found in show variables. What is the level of detail?

Would any detail be too much? Even if the code laid dormant unless turned on, what would users think?

I'm happy to see one of the open source vendors take this leap. I think open information like this is great, since it allows software writers to …

In a previous post, I mentioned the availability of the dtrace extension for Cool Stack's PHP.  Using this extension and the Cool Stack MySQL, it is possible to analyze the performance of your application running on this stack. At JavaOne, we demoed this using the open source MediaWiki and SugarCRM applications.  dtrace is especially useful in analyzing complex multi-tier applications like AMP. Thanks to Angelo Rajadurai for the creation of the scripts that I describe below.

Analyzing PHP calls

So, let's look at a simple dtrace script that counts how many times a particular PHP function is called :

#!/usr/sbin/dtrace -Zqs

php*:::function-entry
/arg0/
{
        @[copyinstr(arg0)]=count();
}

You can copy the …

I've been following the comments to Jamie's latest post and I have to say that most of the people who left comments are not thinking logically about this.  Most (not all) are outraged that Microsoft would try to prevent Jamie from enabling his most excellent TestDriven.Net product on the Express line of products (Visual C# Express, etc).

As a consumer I would love to be able to use plugins in the Express products.  I use Visual C++ Express to code on the MySQL server frequently.  However, I'm smart enough to realize when I've been given something for free. Let me say this slowly and clearly:  Microsoft is a business, not a public service.  They didn't have to make the Express products available at all.  It takes a great deal of time and money to build something as complicated as these …

Ronald Bradford has published the 47th edition of Log Buffer, the weekly review of database blogs, on Technical Notes and Articles of Interest. Get in touch if you’d like to edit and host an edition of Log Buffer on your own blog. The Pythian Group Blog is widely read, so being a part of the [...]

Log Buffer #47: a Carnival of the Vanities for DBAs
June 1st, 2007 - by Ronald Bradford

Welcome to the 47th edition of Log Buffer, the weekly review of database blogs. No time to wait, lets read more about this week’s database blogging activities.

The PostgreSQL Conference for Users and Developers wrapped up this week and Peter Eisentraut gives us a review including the lightning talks and wrap-up session with a charity auction in PGCon Day 4. Meanwhile Alex Gorbachev is at Miracle Scotland Database Forum - Day One, sounds like from his post there is a lot …

I've been following the comments to Jamie's latest post and I have to say that most of the people who left comments are not thinking logically about this.  Most (not all) are outraged that Microsoft would try to prevent Jamie from enabling his most excellent TestDriven.Net product on the Express line of products (Visual C# Express, etc).

As a consumer I would love to be able to use plugins in the Express products.  I use Visual C++ Express to code on the MySQL server frequently.  However, I'm smart enough to realize when I've been given something for free. Let me say this slowly and clearly:  Microsoft is a business, not a public service.  They didn't have to make the Express products available at all.  It takes a great deal of time and money to build something as complicated as these …

Counts, we all love to show counts in our applications. Under a high traffic website, it's visually appealing to show a big number. But the cost of generating that big number realtime can be very expensive on our mySQL backend.

For example:

$sql = SELECT COUNT(*) FROM VERY_BIG_TABLE WHERE key_part1=NUM AND no_key IN (1,2,3) AND key_part2=NUM

Would you think this is fast? In a dev environment yes, but this query has to get the exact row count that meets the requirements of the WHERE clause.

In many cases we use a count to solve a BOOLEAN term in our code, for example

$count_result = db_fetch($sql)

if ($count_result) {
   // do something
} else {
   $SHOW_ERROR = 1;
}

Don't use a count for this purpose. Just do something like

$sql = …

As Roland pointed out, recently a bunch of us took the MySQL Cluster Certification Exam. I was strongly encouraging people to take it (and, in fact, got the majority of people to take it… except those working on urgent customer issues or were rather new to the product).  That’s one of my cunning plans (number 8 IIRC) - to have anybody doing anything to do with MySQL Cluster inside MySQL AB to be certified (in cluster, not insane).

Response from the exam is overwhelmingly positive and as it’s new, afterwards I discussed a few questions with Roland (in fact, all the ones I got wrong). The (good!?) news is that I legitimately brain-farted on some.

As for bragging rights… I currently share the top score. I’ll also (happily) buy a (large) beer …

How can a query like "SELECT * FROM tbl WHERE col IS NULL" return a row where the column has a (non-NULL) value? Read on to find out.