InnoDB background LRU list flushing is not limited by innodb_io_capcity or innodb_io_capacity_max. I’ll prove it in this blog post, but since MySQL experts disagree (or don’t know for sure), I’d like you to prove me wrong. This is not an intro; you’ll need to know all the InnoDB details wrt page flushing.

InnoDB background LRU list flushing is not limited by innodb_io_capcity or innodb_io_capacity_max. I’ll prove it in this blog post, but since MySQL experts disagree (or don’t know for sure), I’d like you to prove me wrong. This is not an intro; you’ll need to know all the InnoDB details wrt page flushing.

Locking is an important concept in databases. They help regulate access to the data, so your SELECT queries return consistent results and DML and DDL statements leave the data and schema in a consistent state. For the data, there are four different transaction isolation levels that influence which locks are taken. The most two commonly used isolation levels are REPEATABLE READ (the default in InnoDB) and READ COMMITTED (the default in some other databases). Both of those are said to provide non-locking reads, but there is a little more to it than that.

Selecting into a user variable causing a lock wait timeout.

One case where reads are always locking is when you explicitly requests locks by adding the FOR SHARE or FOR UPDATE modifiers. However there are also cases where SELECT statements becomes locking due to the way the result of the statement is used. …

There is a number of powerful MySQL storage engines at our disposal, and InnoDB is undoubtedly one of the most popular ones. It is highly reliable and efficient, so it is no wonder that it has become a default storage engine for all MySQL versions from 5.5 on. Let us take a look at its […]

The post What Is InnoDB in MySQL? Tutorial with Examples and Performance Tuning Tips appeared first on Devart Blog.

As some of you likely know, I have a favorable view of ZFS and especially of MySQL on ZFS. As I published a few years ago, the argument for ZFS was less about performance than its useful features like data compression and snapshots. At the time, ZFS was significantly slower than xfs and ext4 except when the L2ARC was used.

Since then, however, ZFS on Linux has progressed a lot and I also learned how to better tune it. Also, I found out the sysbench benchmark I used at the time was not a fair choice since the dataset it generates compresses much less than a realistic one. For all these reasons, I believe that it is time to revisit the performance aspect of MySQL on ZFS.

ZFS Evolution

In 2018, I reported ZFS performance results based on version 0.6.5.6, the default version available in Ubuntu Xenial. The present post is using …

For performance, having a warm InnoDB Buffer Pool is very important. What does that mean ?

A warm buffer pool means that the most used pages (working set) required by the production workload are already loaded in memory (in the buffer pool). If so, MySQL doesn’t need to read the pages from disk every time it requires the most used page and speeds up the process when the needed data is already in memory.

When you start MySQL, by default the InnoDB Buffer Pool is cold and the warm up process can even take days sometimes…

So, you can already deduce that restarting mysqld is a source of having a cold Buffer Pool as it will start empty. Another reason to have a non optimal Buffer Pool is to load it unnecessary pages. This can happen during a logical dump or load. If you regularly do a mysqldump for example (don’t forget that MySQL Shell dump & load is better if you do logical dumps, but introduces also the …

This article focuses on the database storage engines for MySQL that ensure appropriate performance and manage SQL operations for multiple table types. The article examines the differences between the most widely used MySQL storage engines. MySQL is the second most popular Relational Database Management Systems (RDBMS) in the world. Countless services and applications have MySQL […]

The post Storage Engines in MySQL appeared first on Devart Blog.

Recovering to a particular time in the past is called Point-In-Time Recovery (PITR). With PITR you can rollback unwanted DELETE without WHERE clause or any other harmful command.

PITR with Percona XtraBackup is pretty straightforward and perfectly described in the user manual. You need to restore the data from the backup, then apply all binary logs created or updated after the backup was taken, but skip harmful event(s).

However, if your data set is large you may want to recover only the affected database or table. This is possible but you need to be smart when filtering events from the binary log. In this post, I will show how to perform such a partial recovery using Percona XtraBackup, …

Over the decades we have been reading the MySQL error log from the server system file, if there are any issues in MySQL or any unknown restart happened , generally we look at the mysql error log.

By default MySQL error log can be found in the default path /var/log/mysqld.log , or it can be explicitly configured using the variable log_error.

Few drawbacks using MySQL error log as FILE

• Possibility of missing genuine errors while reading lengthy information.
• Filtering of errors for the particular date and timeframes.
• Cannot provide the DB server access to developers because of fear of mishandling DB servers.

To overcome the above issues , from MySQL …

Recently one of our customers ran into an issue, wherein a bad actor(code) from the application had made the wrong update to 16 M records of a critical table in the database, causing the entire production process to go down. The application Team was able to find the bad actor and block it, our Remote DBA was involved in the Data Recovery/Rollback.

Here I would like to discuss possible recovery methods for the above said scenario

Delayed Slave:

A simple and effective way to recover is by using a delayed slave, RDS started supporting this feature from version 5.6.40 and 5.7.22 i.e., you can induce a SQL thread delay-interval for applying the writes to a slave, detailed implementation is covered in our blog here. It’s …