In the MySQL Team, we are currently evaluating potential changes to the default server configuration for MySQL 5.7. For more context, please see my earlier post here.
One of the specific changes we would like to make is with the following three related replication and InnoDB settings:
| Setting | Old Default | New Default |
| binlog_format | STATEMENT | ROW |
| … |
Over the past few months I’ve written a couple of posts about dangerous debt of InnoDB Transactional History and about the fact MVCC can be the cause of severe MySQL performance issues. In this post I will cover a related topic – InnoDB Transaction Isolation Modes, their relationship with MVCC (multi-version concurrency control) and how they impact MySQL performance.
The MySQL Manual provides a decent description of transaction isolation modes supported by MySQL – I will not repeat it here but rather focus on performance implications.
SERIALIZABLE – This is the strongest …
[Read more]The devroom’s schedule is now published on Fosdem’s website.
As you can see, it will be a heavy day full of good content. You can also notice that there won’t be any lunch-time break.
We advise you to then bring your lunch (like a sandwich) with you in the room and eat it between talks or prepare in advance when you will take your break during a talk you don’t want to attend (is it even possible ?).
| Event | Speakers | Start | End |
|---|---|---|---|
| Sunday | |||
| Welcome to MySQL & Friends Devroom | … |
This blog explains how relay log recovery happens in a scenario
where an applier thread (SQL_Thread) is starting for the first
time and its starting position is not available for relay log
recovery operations. If you are using GTIDs with MASTER_AUTO_POSITION then the
following is more or less irrelevant since we then employ a more
resilient repositioning scheme. The potential issue described
here will also not occur if you have employed crash-safe replication settings,
including --sync_master_info=1. With those
disclaimers out of the way, let’s proceed.
Background
A crash-safe slave in MySQL …
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Silly pun, we know. We couldn’t help ourselves.
A while ago I blogged about a potential workaround for MySQL error 1070 that could be used to add a unique constraint with more than 16 columns.
As a reminder here's the error you get when you try to create a unique constraint with more than 16 columns in MySQL:
ERROR 1070 (42000): Too many key parts specified; max 16
parts allowed
The solution I proposed should work, but when I started to implement it I made a couple of changes that merit this follow-up post. One change is fairly generic, and the other is specific to my use case.
The generic change was to only concatenate some of the columns, rather than all of them. Specifically I only need to concatenate N-15 columns. So if I want to have a unique constraint on 20 columns, I can include 15 of those actual columns and then …
[Read more]MySQL 5.6.22 was recently released (it is the latest MySQL 5.6, is GA), and is available for download here.
For this release, there is 1 “Security Note”, 2 “Functionality Changed”, and 5 “Compilation Notes”, all benign, but let me address them:
MariaDB 5.5.41 was recently released (it is the latest MariaDB 5.5), and is available for download here:
https://downloads.mariadb.org/mariadb/5.5.41/
This is a maintenance release, and so there were not too many changes, *but* please take notice as there are 2 very important bug fixes:
2014 was a productive year for the MariaDB Foundation.
Here is a list of some of the things MariaDB Foundation employees
have
accomplished during 2014:
The 3 full-time MariaDB Foundation developers have worked hard to
make MariaDB better:
Some of the main new features Foundation developers have worked
on in 2014 are:
I showed in an earlier post how to drop a whole database in a very safe way (no replication lag at all) and that technique is usable to drop a single table too, but cleaning up a table can take hours if not days to finish, so this is not the most comfortable way to do that. We also don’t want to have even a small spike of replication lag, so we need to find an another solution.
How to remove database in a safe way
When you have to drop a large database, you’ll encounter some
problems, mainly replication…
Read more
What happens when you issue a DROP TABLE command? The table has
to be removed from the table dictionary – which is a fast, atomic
operation – and has to be removed from file system too. If you
use older version than 5.5.10 you have to calculate with a huge
amount of time if your buffer pool is big, because the server
will scan through the pages there, checking if anything is in
memory from that …