TokuDB Hot Backup Now a MySQL Plugin

Feb 05, 2015 | MySQL

In the recently released TokuDB 7.5.5 the implementation of TokuDB hot-backup moved from a patch to the MySQL Server, to MySQL Plugin.  Why did we make this change? TokuDB hot backup makes a transactionally consistent copy of the TokuDB files while applications continue to read and write these files.  Christian Rober wrote a nice series […]

TokuDB 7.5.5 is now available

Jan 29, 2015 | MySQL

Tokutek is pleased to announce the general availability of TokuDB 7.5.5. The notable changes since TokuDB 7.5.3 are: Rebased onto MySQL 5.5.41 and MariaDB 5.5.41 to integrate the latest changes Improved TokuDB lock timeout logging Added several optimize table options for TokuDB tables including the ability to throttle the optimize operation, selectively pick indexes to optimize, optimize […]

Scaling TokuDB Performance with Binlog Group Commit

Dec 17, 2014 | MySQL

TokuDB offers high throughput for write intensive applications, and the throughput scales with the number of concurrent clients.  However, when the binary log is turned on, TokuDB 7.5.2 throughput suffers.  The throughput scaling problem is caused by a poor interaction between the binary log group commit algorithm in MySQL 5.6 and the way TokuDB commits […]

An Updated Description of Clustering Keys for TokuDB

Aug 06, 2014 | MySQL

Covering indexes can result in orders of magnitude performance improvements for queries. Bradley’s presentation on covering indexes describes what a covering index is, how it can effect performance, and why it works. However, the definition of a covering index can get cumbersome since MySQL limits the number of columns in a key to 16 (32 on […]

Why TokuDB does not use the ‘uint3korr’ function

Apr 08, 2014 | MySQL

The ‘uint3korr’ function inside of the mysqld server extracts a 3 byte unsigned integer from a memory buffer. One use is for ‘mediumint’ columns which encode their value in 3 bytes. MySQL 5.6 and MariaDB 10.0 claims to have optimized this function for x86 and x86_64 processors. There is a big comment that says:

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Uninitialized data in the TokuDB recovery log

Apr 03, 2014 | MySQL

A TokuDB MySQL test run with valgrind reported an uninitialized data error when writing into the TokuDB recovery log.

TokuDB should not be storing uninitialized data into its files, so I need to find the the code that neglected to initialize the memory that eventually got written to the recovery log. An update SQL […]

Lock Escalation and Big Transactions in TokuDB and TokuMX

Mar 27, 2014 | MySQL

We have seen TokuDB lock escalation stall the execution of SQL operations for tens of seconds. To address this problem, we changed the lock escalation algorithm used by TokuDB and TokuMX so that the cost of lock escalation only affects big transactions. We also eliminated a serialization point when running lock escalation. Transactions in TokuDB […]

Big trouble with zero-length character columns in TokuDB

Mar 17, 2014 | MySQL

What good is a zero-length character column in a MySQL table? A zero-length character column has type of ‘char(0)’. If it is nullable, then it can at least store one bit. If it is not nullable, then the value for this column in all rows is a null string. IMO, not very useful. However, the […]

What does the ‘Incorrect key file for table’ error mean?

Nov 19, 2013 | MySQL

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 […]

Problems with Multiple XA Storage Engines in MySQL 5.6

Oct 23, 2013 | MySQL

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 […]

Interactive Debugging of Transaction Conflicts with TokuDB

Oct 16, 2013 | MySQL

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 […]

A TokuDB Stall Caused by Conflicting Transactions When Opening a Table

Oct 03, 2013 | MySQL

One of our customers reported that ‘create table select from’ statements stall for a period of time equal to the TokuDB lock timeout.  This indicated a lock conflict between multiple transactions.  In addition, other MySQL clients that were opening unrelated tables were also stalled.  This indicated that some shared mutex is held too long.  We […]

A TokuDB Stall Caused by a Big Transaction and How It was Fixed

Sep 20, 2013 | MySQL

One of our customers sometimes observed lots of simple insertions taking far longer than expected to complete. Usually these insertions completed in milliseconds, but the insertions sometimes were taking hundreds of seconds. These stalls indicated the existence of a serialization bug in the Fractal Tree index software, so the hunt was on. We found that […]

Fast Updates with TokuDB

Feb 12, 2013 | MySQL

With TokuDB v6.6 out now, I’m excited to present one of my favorite enhancements: fast updates with TokuDB. Update intensive applications can have their throughput limited by the random read capacity of the storage system. The cause of the throughput limit is the read-modify-write algorithm that MySQL uses when processing update statements. MySQL reads a […]

How We Spent a Tuesday Fixing a MySQL Replication Bug

Jul 16, 2012 | MySQL

We found a simple XA transaction that crashes MySQL 5.5 replication. This simple transaction inserts a row into an InnoDB table and a TokuDB table. The bug was caused by a flaw in the logging code exposed by the transaction’s use of two XA storage engines (TokuDB and InnoDB). This bug was fixed in the […]

Hot Table Optimization with MySQL

Jun 28, 2012 | MySQL

Table optimization is a necessary evil; tables sometimes need to be optimized to reclaim space or to improve query performance.  Unfortunately, MySQL blocks writes to a table while it is being optimized.  Because optimization time is proportional to the table size, writes can be blocked for a long time.  Fractal Tree indexes support online optimization; […]

Addressing Hot Schema Changes in MySQL

Jun 14, 2012 | MySQL

As ones data model evolves changing the database schema becomes painful, especially for big databases where the table must be taken offline. Fortunately, Tokutek introduced online schema changes starting in TokuDB v5.0. A typical schema change involves adding or deleting a column from a table. These operations usually require the table to be rebuilt offline since the […]

Speeding Up TPCC Table Loads by 8x with TokuDB v5.0

Jun 17, 2011 | MySQL

Percona’s TPCC for MySQL toolset allows one to measure the query performance for an OLTP workload on various MySQL storage engines. The toolset includes a program to load the database tables, and a program to run queries and measure performance. We have found Percona’s TPCC toolset to be extremely useful for tuning our software. However, […]

Loading Air Traffic Control Data with TokuDB 4.1.1

Aug 27, 2010 | MySQL

TokuDB has a big advantage over B-trees when trickle loading data into existing tables. However, it is possible to preprocess the data when bulk loading into empty tables or when new indexes are created. TokuDB release 4 now uses a parallel algorithm to speed up these types of bulk insertions. How does the parallel loader […]

TokuDB speeds up “replace” and “insert ignore” operations by relaxing the affected rows constraint

Aug 03, 2010 | MySQL

In posts on June 30 and July 6, we explained how implementing the commands “replace into” and “insert ignore” with TokuDB’s fractal trees data structures can be two orders of magnitude faster than implementing them with B-trees. Towards the end of each post, we hinted at that there are some caveats that complicate the story […]