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MySQL 5.6 - What’s New

I’ve finally had the time to go through the release notes and documentation of the recent release of MySQL 5.6. My first throughts when skimming over the announcement were:

  1. why is online DDL support so low on the list?
  2. why so much of the announcement is about performance?
  3. how is Oracle going to position the Memcached-based access to InnoDB considering their other key-value database Oracle NoSQL database?

Here’s the opening part of the “DBA and Developer Guide to MySQL 5.6:

At a glance, MySQL 5.6 is simply a better MySQL with improvements that enhance every functional area of the database kernel, including:

  • Better Performance and Scalability
    • Improved InnoDB storage engine for better transactional throughput
    • Improved Optimizer for better query execution times and diagnostics
  • Better Application Availability with Online DDL/Schema changes
  • Better Developer Agility with NoSQL Access with Memcached API to InnoDB
  • Improved Replication for high performance, self-healing distributed deployments
  • Improved Performance Schema for better instrumentation
  • Improved Security for worry-free application deployments
  • And other Important Enhancements

Almost half of the document focuses on the performance improvements in the InnoDB. If this is the part that interests you, I strongly encourage you to read the doc as my notes about this part are very short:

  • InnoDB did a lot of improvements in handling threads and locks
  • this will allow MySQL 5.6 to work more efficiently on beefier machines with over 24 cores. The shape of the TPS/CPU threads looks almost linear.
  • the transactional throughput graph shows improvements, but the shape suggests that MySQL 5.6 tops at around 96 concurrent connections
  • SSDs are mentioned but after digging a bit deeper, it’s difficult to say how much of a difference these changes make.

The next section covers online DDL/schema changes. To my surprise, it’s only a paragraph long, while I was expecting more details considering how many complains I’ve heard about this in the past and how advanced PostgreSQL is. There’s indeed another document, “Overview of Online DDL“, that provides more details:

Overview of Online DDL

Basically, starting with this version, many DDL operations do allow concurrent data access, but the many of the operations remain very expensive (some requiring copying all data row by row). Better, but not awesome.

The next section talks about the Memcached-based API for accessing InnoDB data, basically a mechanism offering key-value access that overpasses the SQL layers. I couldn’t find a direct answer to my question “how is Oracle positioning this solution compared to Oracle NoSQL database”. Plus the use of NoSQL term feels weird: “NoSQL access to InnoDB”, “the new NoSQL API for InnoDB”, “NoSQL benchmarking”. I wouldn’t go as far to say that Oracle’s marketing is trying to trivialize the term NoSQL, but it definitely feels like it was one of the top checkboxes that the department had to check.

The last part I was interested into (based on my past experience of completely random and unexplained replication failures) was about replication improvements. I didn’t get much out of this document and I’ll have to read the “MySQL replication: High availability - building a self-healing replication topology whitepaper“:

  • global transaction identifiers: “enable replication transactional integrity to be tracked through a replication master/slave topology”
  • a new set of Python utilities to use global transaction identifiers
  • schema level multi-threaded slave replication
  • new row-based replication
  • new crash-safe slaves: “stores Binlog positional data within tables so slaves can automatically roll back replication to the last committed event before failure, and resume replication without administrator intervention” (nb: this seems to be the issue I’ve seen before when being responsible for a production master-slave x 2 setup).

Technically, MySQL 5.6 seems a solid improvement over the previous version. But Oracle also needs to address the lack of openness concerns raised by Fedora and OpenSUSE communities.

Original title and link: MySQL 5.6 - What’s New (NoSQL database©myNoSQL)