The latest from the MySQL community

The LZMA algorithm implemented by the xz compression software package is one of the compression algorithms used by TokuDB for MySQL and TokuMX for MongoDB.  Unfortunately, valgrind's memcheck reports an uninitialized variable problem in the …

I personally have always enjoyed the Ubuntu Developer Summits (UDS), but nowadays they have been converted to the Ubuntu Online Summits (UOS). Attending them is not always convenient (timezone issues, might be travelling, etc.) so I watched the recorded video of a session I was interested in: MySQL & Variants in 16.04.

My key takeaways

1. Ubuntu 16.04 Xenial Xerus is an LTS release.
2. The term “cross-grade” is used a lot (it is not about downgrading/upgrading, but being able to use MySQL or MariaDB or Percona Server interchangeably)
3. It would be nice to see MySQL 5.7 in this release (for Xenial as well as Debian Stretch). From Oracle there is a new packager taking over the task (Lars)
4. MySQL 5.5 is still the default in Debian, and there needs to be upgrades tested between 5.5 to 5.7 (it looks …

Continuing on with the cloud theme, I think its worth noting that since mid-2014, Rackspace has offered MariaDB (as well as MySQL and Percona Server) in the cloud, as part of their Cloud Databases offering. It’s powered by OpenStack.

Now there is an additional “High Availability instance” being offered — this gives you up to two replicas per database instance, you have the ability to load balance reads across all replicas (pretty standard), but the cool thing to try out: failover is automatic. …

Some time ago, Peter Boros at Percona wrote this post: Rotating MySQL slow logs safely. It contains good info, such as that one should use the rename method for rotation (rather than copytruncate), and then connect to mysqld and issue a FLUSH LOGS (rather than send a SIGHUP signal).

So far so good. What I do not agree with is the additional construct to prevent slow queries from being written during log rotation. The author’s rationale is that if too many items get written while the rotation is in process, this can block threads. I understand this, but let’s review what actually happens.

Indeed, if one were to do lots of writes to the slow query log in a short space of time, a write could block while waiting.

Is the risk of this occurring greater during a logrotate operation? I doubt it. A FLUSH LOGS has to …

Today I received about five emails with the subject: 3 Big Announcements from MariaDB. Maybe you did as well (else, read it online). October has brought on some very interest announcements, and I think my priority for the big announcements vary a little:

1. MariaDB Server is now available on Amazon RDS – you wouldn’t believe how many people ask for this, as many now deploy using Amazon …

The Korean MySQL Power User Group gets a special guest speaker next weekend (Oct 31 2015 – 4pm – 4:33’s offices in Gangnam — nearest train stop is Samseong station, Line 2 — post requires Cafe Naver login) — Mark Callaghan (Small Datum, @markcallaghan, and formerly High Availability MySQL). I’ve been to many of their meetups, and I think this is a great opportunity for many DBAs to learn more about how Mark helps make MySQL and MongoDB better …

Last week we had the MySQL Meetup with MariaDB Developers in Amsterdam, which went on easily for about 3.5 hours. Thanks to all for listening (these were lightning talks, not with a strict 5 minute clock with Q&A thrown in), and Daniël van Eeden for organising this at the eBay offices (whom kindly provided pizza, beer and soft drinks as well). We had many talks, and I’ve managed to put up most of the slides into a Google Drive folder, so feel free to access the …

People at Intel started the pmem library project some time ago, it’s open to the broader community at GitHub and  other developers, including Linux kernel devs, are actively involved.

While the library does allow interaction with an SSD using a good-old-filesystem, we know that addressing SSD through SATA or SAS is very inefficient. That said, the type of storage architecture that SSD uses does require significant management for write levelling and verifying so that the device as a whole actually lasts, and your data is kept safe: in theory you could write to an NVRAM chip, and not know when it didn’t actually store your data properly.

But there are other technologies, such as Memristor (RRAM) and Phase Change Memory …

A common way to implement point in time recovery capability is:

to regularly do a full backup of a database, and to save the binary logs of that database (or from its master if doing backups on a slave).

When point in time recovery is required you need to:

restore a backup, and apply the binary logs up to the point of recovery.

(Step # 2 and # b above are the ones that will be simplified

Update 2016-01-30: restarting the IO_THREAD might be considered useful in some situations (avoiding MDEV-9138).  Look for "in contrast, if the IO thread was also stopped first" in MDEV-6589 for more information.

In a previous post, I listed some sequences of commands that you should not run on a MariaDB slave that is lagging and which is using the GTID protocol.  Those are the following (do not