(Reposted from the HailDB Blog. See also the announcement on the Drizzle Blog.)
We’ve made our first HailDB release! We’ve decided to make this a very conservative release. Fixing some minor bugs, getting a lot of compiler warnings fixed and start to make the name change in the source from Embedded InnoDB to HailDB.

Migrating your software to use HailDB is really simple. In fact, for this release, it shouldn’t take more than 5 minutes.

Highlights of this release:

• A lot of compiler warnings have been fixed.
• The build system is now pandora-build.
• some small bugs have been fixed
• Header file is now haildb.h instead of innodb.h
• We display “HailDB” instead of …

A couple of weeks ago one of my colleagues and I worked on a data corruption case that reminded me that sometimes people make unsafe assumptions without knowing it. This one involved SAN snapshotting that was unsafe.

In a nutshell, the client used SAN block-level replication to maintain a standby/failover MySQL system, and there was a failover that didn't work; both the primary and fallback machine had identically corrupted data files. After running fsck on the replica, the InnoDB data files were entirely deleted.

When we arrived on the scene, there was a data directory with an 800+ GB data file, which we determined had been restored from a SAN snapshot. Accessing this file caused a number of errors, including warnings about accessing data outside of the partition boundaries. We were eventually able to coax the filesystem into truncating the data file back to a size that didn't contain invalid pointers and could be read without …

I am speaking in a few days at OSCON 2010 in Portland, Oregon. My talk, “MySQL Bottleneck Hunters – How Schooner Increased MySQL Performance by 8x” is about how Schooner optimized MySQL to run on modern hardware with flash memory. Come on by if you’re at OSCON!

Here’s the abstract:

MySQL Bottleneck Hunters – How Schooner Increased MySQL Performance by 8x — Thursday, July 22, 2010 at 11:30am

MySQL users have an insatiable need for speed, capacity, and availability, all at a reasonable cost. This session will provide technical overview of the approach that Schooner engineering took to optimize MySQL Enterprise and InnoDB with flash memory, multi-core processors, and DRAM to achieve an 8x …

I recently did a quick analysis of the distribution of writes to InnoDB's log files. On a high-traffic commodity MySQL server running Percona XtraDB for a gaming workload (mostly inserts to the "moves" table), I used strace to gather statistics about how the log file writes are distributed in terms of write size. InnoDB writes to the log files in multiples of 512 bytes. Mark Callaghan explained this and some of its performance implications here. How many big writes does InnoDB do, and how many small writes?

First, I found out the file descriptor numbers of the log files:

# lsof -p $(pidof mysqld) | grep ib_log
mysqld  29772 mysql    8uW  REG                8,2   268435456   7143989 /var/lib/mysql/ib_logfile0
mysqld  29772 mysql    9uW  REG                8,2   268435456   7143993 /var/lib/mysql/ib_logfile1

The …

This is the first of a series of posts about business intelligence tools, particularly OLAP (or online analytical processing) tools using MySQL and other free open source software. OLAP tools are a part of the larger topic of business intelligence, a topic that has not had a lot of coverage on MPB. Because of this, I am going to start out talking about these topics in general, rather than getting right to gritty details of their performance.

I plan on covering the following topics:

1. Introduction to OLAP and business intelligence. (this post)
2. Identifying the differences between a data warehouse, and a data mart.
3. Introduction to MDX queries and the kind of SQL which a ROLAP tool must generate to answer those queries.
4. Performance challenges …

There’s lots of buzz lately about the so-called “open-core” business model of Marten Mickos’s new employer. But this is nothing new. Depending on how you define it, InnoDB is “open-core,” and has been for a long time. The InnoDB Hot Backup (ibbackup) tool was always closed-source. Did anyone ever cry foul and claim that this made InnoDB itself not open-source, or accuse Innobase / Oracle of masquerading as open-source? I don’t recall that happening, although sometimes people got suspicious about the interplay between the backup tool and the storage engine. Generally, though, the people I know who use InnoDB Hot Backup have no gripes about paying for it.

What is the difference between open-source with closed-source accessories, and …

For a long time long types like BLOB, TEXT were not supported by Percona InnoDB Recovery Tool. The reason consists in a special way InnoDB stores BLOBs.

An InnoDB table is stored in a clustered index called PRIMARY. It must exist even if a user hasn't defined the primary index. The PRIMARY index pages are identified by 8-bytes number index_id. The highest 4 bytes are always 0, so index_id is often notated as o:<4 bytes number>, e.g. 0:258. The pages are ordered in a B-tree. Primary index is used as a key. Inside a page records are stored in a linked list.

InnoDB page by default is 16k. Obviously if a record is too long, a single page can't store it. If the total record size is less than UNIV_PAGE_SIZE/2 - 200 (this is roughly 7k) then the full record is stored in the page of PRIMARY index. Let's call it internal. In InnoDB sources they have type FIL_PAGE_INDEX*. If the record is longer than 7k bytes, only first 768 bytes of …

In my last post, I discussed how to troubleshoot InnoDB locks using the new InnoDB Plugin’s new Information Schema tables.

However, that got me to thinking about how many MySQL 5.1 users who have still not switched to use the plugin as opposed to the built-in version of InnoDB.

There are many advantages to using the plugin as opposed to the built-in version (aside from just the new I_S tables, and more importantly, numerous performance enhancements), and it’s breeze to set up, so I wanted to provide a quick start guide to using the new InnoDB plugin.

Note that the …

Tracking down InnoDB lock information using the new Information Schema tables provided with the InnoDB plugin has never been easier.

Long story short, the other day I was trying to identify what transaction was holding the lock for a particular UPDATE. The UPDATE would not complete and kept timing out with “Lock wait timeout exceeded; try restarting transaction”.

Of course I checked the output of SHOW ENGINE INNODB STATUS. From that output, I could tell it was the replication thread holding the lock, *since* it was the only other transaction running. But I could not verify this with output, it just had to be the case.

Next I enabled the InnoDB lock monitor, and examined that output too. Here, it showed more detail on the locks being held, however, it only shows the first 10 locks held by the replication thread. In this case, the …

Again, another simple test. Same basic tuning as yesterday, and the table schema is the same:
CREATE TABLE `t1` (
`c1` int(11) NOT NULL AUTO_INCREMENT,
`c2` char(100) DEFAULT NULL,
PRIMARY KEY (`c1`)
);
The table is again filled with 1.3 million rows, but this time I'm doing an UPDATE. The update is again a simple primary key update:
UPDATE t1 SET c2 = CONCAT('xxx', RAND(), 'yyy') WHERE c1 = <random value 1 - 1000000>;
I run this on the Maria, InnoDB and MyISAM engines. The issues with the MyISAM and Maria engines here is that they lack row level locking. In MariaDB 5.1.47, the InnoDB version is 1.0.6, so it is more scalable than what it used to be. The testbench is not an incredibly hot machiine, just a 4 core AMD box.

I run the test in some different configurations, using a single thread, using 10 threads and using 100 threads. Here we can see that InnoDB Row-level locking …