An index is a data structure that sorts a number of records on one or more fields, and speeds up data retrieval. This is to avoid scanning through the disk blocks that a table spans, when searching through the database. So, what kind of indexes are available in MySQL and how do we use them to get the most performance? This will be the topic for this blog. 

This is the twelfth installment in the ‘Become a MySQL DBA’ blog series. Our previous posts in the DBA series include Deep Dive pt-query-digest, Analyzing SQL Workload with pt-query-digest, …

Well the new things are cool to test and learn. But it is not possible every time, to have smooth testing process. if you can’t get right software on your hand.

So there are great articles about this new plugin here you can follow all of them: Group Replication Topics

I must say that, plugin available for download as source code and as for Oracle Linux 6 x86_64 from -> labs.mysql.com

So if you want to try it with MySQL 5.7.8-rc2 on Ubuntu you should compile it with MySQL. But you will not be able to compile due to well known ‘boost’ dependency -> see BUG #78600

UPDATE to BUG 78600:

Pedro Gomes clarified the reason of …

Indexes are separate data structures that provide alternate pathways to finding data. They can and do generally speed up the processing of queries and other DML commands, like the INSERT, UPDATE, REPLACE INTO, and DELETE statements. Indexes are also called fast access paths.

In the scope of the InnoDB Database Engine, the MySQL database maintains the integrity of indexes after you create them. The upside of indexes is that they can improve SQL statement performance. The downside is that they impose overhead on every INSERT, UPDATE, REPLACE INTO, and DELETE statement, because the database maintains them by inserting, updating, or deleting items for each related change in the tables that the indexes support.

Indexes have two key properties—usability and visibility. Indexes are both usable and visible by default. That means they …

For learning, testing and keep up with things, one might want to install/update the MySQL version to the latest DMR (Development Milestone Release). At the time of this writing the latest DMR for MySQL is  MySQL Community Server 5.7.8-rc. Having chosen Ubuntu server as my operating system and since this is a development version hence not yet part of an official Ubuntu release, you have to install

When it’s not possible to remove SQL statements that are unnecessary and the rate of change of common data is relatively low, caching SQL results can provide a significant performance boost to your application and enable additional scalability of your database server.

MySQL Caching

The MySQL query cache can provide a boost in performance for a high read environment and can be implemented without any additional application overhead. The following is an example using the profiling functionality to show the execution time and the individual complexity of a regular SQL statement and a subsequent cached query:

SET GLOBAL query_cache_size=1024*1024*16;
SET GLOBAL query_cache_type=1;
SET PROFILING=1;
SELECT name FROM firms WHERE id=727;
SELECT name FROM firms WHERE id=727;
SHOW PROFILES;

…

In addition to creating new indexes to improve performance, you can improve database performance with additional schema optimizations. These optimizations include using specific data types and/or column types. The benefit is a smaller disk footprint producing less disk I/O and results in more index data being packed in available system memory.

Data Types

Several data types can be replaced or modified with little or no impact to an existing schema.

BIGINT vs. INT

When a primary key is defined as a BIGINT AUTO_INCREMENT data type, there is generally no requirement why this datatype is required. An INT UNSIGNED AUTO_INCREMENT datatype is capable of supporting a maximum value of 4.3 billion. If the table holds more than 4.3 billion rows, other architecture considerations are generally necessary before this requirement.

The impact of modifying a BIGINT data type to an INT data type is a 50 percent reduction …

Replication in MySQL is the dynamic process of synchronizing data between a primary (master) database server and one or more secondary (slave) database servers in near-real time. Using this process, it’s possible to create copies of one or more databases so that even if the primary server fails, data can still be recovered from one of the secondary servers.

Replication is essential for many applications, and the lack of replication support was a major drawback to MySQL compared to other relational database management systems (RDBMSs). MySQL 3.23 was the first version to introduce replication support, and support has improved continually in subsequent versions. However, MySQL is still best suited for one-way replication, where you have one master and one or more slaves.

TIP

As much as possible, try to use the same version of MySQL for both the master and slave server(s). A version …

You might need to restore corrupted tables (or even an entire database) from your backups and use the update logs if a table gets damaged or deleted by accident. In case of relatively minor damage, however, MySQL provides several options for table repair. This next section deals with what you can do if this is the case.

Checking Tables for Errors

The first thing to do if you suspect something is wrong is to check the table for errors. The myisamchk utility is one way to check a table. To invoke this utility, execute the command myisamchk table-file.

Because myisamchk requires exclusive access to the tables, a good idea is to take the server offline before running it. This way, you needn’t worry about coordinating access between clients. In addition, you can run several options when you check a table for errors, as shown in Table 1.

The following example runs myisamchk with the …

Recently we announced MySQL Data Recovery Portal. Here we automated some data recovery routines and published web interface to them.

First, it was a tool to estimate recovery chances from corrupted InnoDB tablespaces.

Now it’s even more exciting and useful feature – recovery table structure from FRM files online.

There are several methods to recover MySQL table structure from FRM files.

On MySQL Data Recovery Portal we utilize a combination of them.

Fake table method

The idea is to create a dummy InnoDB table, replace its .frm file with .frm file we want to recover and run SHOW CREATE TABLE.

Let’s say we have actor.frm and we want to get structure of table actor.

Algorithm is following:

Create a dummy table with the same name, actor. The …

My job is almost completely reliant upon my ability to perform work in lab of virtual machines. Almost every action plan I write is tested locally. When I need to troubleshoot an issue for a client one of the most common first steps I’ll perform is attempting to recreate the issue in a virtual environment so I can work on it there without the risk of impacting client data.

I believe that having a place to test and grow your skills is an absolute necessity for anyone working in the IT field today regardless of your specialization, even if you’re an IT generalist. But every now and then I hear about individuals who have issues with their virtual machines or with the virtual environment provided by their employer, so I figured this was a good time to share my method of creating a virtual lab. More specifically, one that allows you to do virtual work on a commodity laptop, one that won’t break down if you lose connectivity, one that …