William Zola over at MongoDB gave a great talk called “The (Only) Three Reasons for Slow MongoDB Performance”. It reminded me of an interesting characteristic of updates in MongoDB. Because MongoDB’s main data store is a flat file and secondary indexes store offsets into the flat file (as I explain here), if the location of a document changes, corresponding entries in secondary indexes must also change. So, an update to an unindexed field that causes the document to move also causes modifications to every secondary index, which, as William points out, can be expensive. If a document has indexed an array, this problem is exacerbated.

What …

You love MySQL and MariaDB for its ease of deployment, but what if you could increase performance and save significant time and money when your application starts to scale without having to change your applications?
Register Now!

SPEAKER: Tim Callaghan, VP of Engineering at Tokutek
DATE: Tuesday, January 28th
TIME: 1pm ET

Join this interactive webinar with Tokutek’s VP of Engineering, Tim Callaghan, as he walks through the potential pitfalls when using MySQL or MariaDB for Big Data applications, and how to effectively use TokuDB to increase performance, reduce database size and achieve true schema agility.

Attend this webinar to learn:

Don't look at an industry benchmark here, it's a real client story.

200 Billion records in a month and it should be transactional but not durable.

For regular workload we use LOAD DATA INFILE into partitioned InnoDB, but here we have estimated 15TB of RAID storage. This is a lot of disks and it can't no more stay inside a single server internal storage.

MariaDB 5.5 come with TokuDB storage engine for compression, but is it possible in the time frame impose by the workload?

We start benchmarking 380G of raw input data files,  6 Billion rows.

First let's check the compression with the dataset.


Great job my TokuDB 1/5, without tuning a single parameter other than durability! …

What does it mean if MySQL returns the ‘Incorrect key file for table’ error for one of my queries? The answer is complicated and depends on which storage engine is returning the error. We have debugged two cases which we describe here.

File system out of space

When running the random query generator, one of the queries failed.

Query: SELECT * FROM (mysql . general_log AS table1 INNER JOIN INFORMATION_SCHEMA . INNODB_BUFFER_PAGE AS table2 
ON ( table2 . SPACE = table1 . user_host ) ) ORDER BY table1 . thread_id LIMIT 168 
failed: 126 Incorrect key file for table '/data/mysql7/performance_schema_vardir/tmp/#sql_6b8_17.MYI'; 
try to repair it

Since this query requires a sort, MySQL creates a hidden temporary table called ‘#sql_6b8_17.MYI’ to hold the intermediate results. While the query was executing, some operation performed on the MyISAM table returned an error. What could it be?

MySQL maps the …

Attending Percona Live in London next week?

Don’t miss the chance to hear Tokutek’s Vice President of Engineering, Tim Callaghan, discuss how to use your MySQL knowledge to become an instant MongoDB Guru and the advantages of using Fractal Tree® indexes in MySQL and MongoDB. Tim will be speaking about these topics in two separate sessions at 12:00pm and 5:00pm on November 12.

For more information on these sessions and Percona Live-London, visit https://www.percona.com/live/london-2013/users/tim-callaghan.

You love MySQL for its ease of deployment – but are you worried about how your application will perform when it starts to scale?

SPEAKER: Gerry Narvaja, Tokutek
DATE: Wednesday, November 6th
TIME: 1pm ET
Register Now!

Join this interactive webinar with Gerry Narvaja of Tokutek as he walks through the potential pitfalls when using MySQL for Big Data applications, how you can avoid unnecessary tolls on time and resources and tips on how to get the most out of your MySQL applications with open source TokuDB.

Attend this webinar to learn how to:

• dramatically increase performance without having to rewrite code
• reduce the total cost of your servers and flash/SSD storage
• perform hot schema changes

The …

While integrating TokuDB into MySQL 5.6, we found that MySQL 5.6 does not support more than one XA storage engine. For example, there is an assert in the ha_recover function that fires when the total number of XA storage engines is greater than one. After disabling this assert, we found lots of bugs in the MySQL 5.6 implementation of the TC_LOG_MMAP class, which is used when running with the binlog turned off.

There are two alternatives that we know of to fix this problem in MySQL 5.6:

• First, we could merge code from MariaDB 5.5 into MySQL 5.6. The advantage of this approach is that we have been running this code with TokuDB in MariaDB 5.5 for a long time, so we have confidence in its correctness.
• Second, we found that MySQL 5.7.2 has made changes to allow multiple XA storage engines. This is great news for TokuDB since we have one less MySQL patch to worry about. Our simple scan of the MySQL 5.7 source showed …

The upcoming Percona Live London conference, November 11-12, features quite a number of talks about the latest MySQL features and related technologies. There will be a lots of talks about the new MySQL 5.6 features:

• Opening keynote highlights MySQL 5.6 new features.
• New InnoDB Compression talk will cover the new compression algorithm, implemented by Facebook and included in MySQL 5.6.
• New  …

I am developing a concurrent application that uses TokuDB to store its database. Sometimes, one of my SQL statements returns with a ‘lock wait timeout exceeded’ error. How do I identify the cause of this error? First, I need to understand a little bit about how TokuDB transactions use locks. Then, I need to understand how to use the MySQL information schema to look at the current state of the locks.

Transactions and Locks

TokuDB uses key range locks to implement serializable transactions. These locks are acquired as the transaction progresses. The locks are released when the transaction commits or aborts.

TokuDB stores these locks in a data structure called the lock tree. The lock tree stores the set of range locks granted to each transaction. In addition, the lock tree stores the set of locks that are not granted due to a conflict with locks granted to some other transaction.

TokuDB 7.1 provides access to …

Today we released TokuDB v7.1, which includes the following important features and fixes:

• Added ability for users to view lock information via information_schema.tokudb_trx, information_schema.tokudb_locks, and information_schema.tokudb_lock_waits tables.
• Changed the default compression to zlib and default basement node size to 64K.
• Changed default analyze time to 5 seconds.
• Added server variable to control amount of memory allocated for each bulk loader. In prior TokuDB versions each loader allocated 50% of the available TokuDB cache.
• Changed table close behavior such that all data for the table remains in the cache (and is not flushed immediately).
• Removed user reported stalls due to cache pressure induced by the bulk loader, lock tree escalation, and a particular open table stall.
• Several bugs and behavioral issues reported by users. …