Based on MySQL 5.7.13, including all the bug fixes in it, Percona Server 5.7.13-6 is the current GA release in the Percona Server 5.7 series. Percona’s provides completely open-source and free software. All the details of the release can be found in the …[Read more]
I was recently asked this question by an experienced academic at the NY Oracle Users Group event I presented at.
Does MySQL support ACID? (ACID is a set of properties essential for a relational database to perform transactions, i.e. a discrete unit of work.)
Yes, MySQL fully supports ACID, that is Atomicity, Consistency, Isolation and Duration. (*)
This is contrary to the first Google response found searching this question which for reference states “The standard table handler for MySQL is not ACID compliant because it doesn’t support consistency, isolation, or durability”.
The question is however not a simple Yes/No because it depends on timing …[Read more]
Recently I received a question from a user about one of my earlier blog posts. Since it wasn’t sent as a comment, I will answer it here. The question:
> I am reading your article:
> Full table scan locks whole table.
> Some bad select (read) query can do full table scan on InnoDB, does it lock whole table please?
> My understanding was that SELECT (read) blocks another DML only in MyISAM.
To answer this question, we to need understand two different concepts: locking and …[Read more]
For some reason I do not see numerous public announcements about
recent MySQL 5.7.13 release, even though it happened
a couple of days ago formally. Maybe that's because we do not
have any really "big" new features in this release (new ->> operator for introduced
though for those who, unlike me, care about JSON). Still there
are many fixes for bugs previously reported by Community (or
Oracle engineers, but still in public bugs database), and I'd
like to discuss some of them.
Let me start with the bug that was NOT fixed though, Bug #81093, "mysqld_multi not included in mysql-community-server package", reported by Georgi Iovchev and …
In this blog post, we’ll discuss how to use multi-threaded LRU flushing to prevent bottlenecks in MySQL.
In the previous post, we saw that InnoDB 5.7 performs a lot of single-page LRU flushes, which in turn are serialized by the shared doublewrite buffer. Based on our 5.6 experience we have decided to attack the single-page flush issue first.
Let’s start with describing a single-page flush. If the working set of a database instance is bigger than the available buffer pool, existing data pages will have to be evicted or flushed (and then evicted) to make room for queries reading in new pages. InnoDB tries to anticipate this by maintaining a list of free pages per buffer pool instance; these are the pages that can be immediately used for placing the newly-read data pages. The target length of the free page list is governed by the …[Read more]
MySQL 5.7.12 was released more than 2 weeks ago. New features
introduced there in a form of "rapid plugins" are widely
discussed, but I am more interested in bugs reported by MySQL
Community users that are fixed there. Unfortunately I do not see
MySQL Community Release Notes by Morgan (like this) for quite a some time, so I have to
continue describing key bug fixes and name people who reported
and verified bugs in my "Fun with Bugs" series.
As usual, let's start with InnoDB bugs fixed:
- Bug #80070 - "allocated_size and file_size differ if create general tablespace outside datadir". It was reported by my former colleague from Percona …
InnoDB in MySQL 5.7 introduced for the first time the ability to create a general tablespace and assign multiple tables to it. These tablespaces can be assigned anywhere on the system. They can even be assigned a smaller block size so that they can contain compressed tables that use that size as their key_block_size.…
You would think MySQL storage engines are fairly independent of each other, even in the same environment. Enabling one, or changing its configuration, logically should have no impact on the performance of other engines (such as InnoDB) when they are accessing tables. The reality, however, is more complicated than that!
Now that we’ve shipped TokuDB, we’ve been getting feedback from our community and customers that enabling TokuDB might negatively affect performance – even for queries that don’t touch TokuDB tables (and in some cases, even when TokuDB is kept completely idle).…[Read more]
Based on MySQL 5.7.11, including all the bug fixes in it, Percona Server 5.7.11-4 is the current GA release in the Percona Server 5.7 series. All of Percona’s software is open-source and free, …[Read more]
Percona is glad to announce the release of Percona Server 5.5.48-37.8 on March 4, 2016. Based on MySQL 5.5.48, including all the bug fixes in it, Percona Server 5.5.48-37.8 is now the current stable release in the 5.5 series.