Percona Server 5.5.15-21.0

Percona is glad to announce the release of Percona Server 5.5.15-21.0 on August 31, 2011 (Downloads are available here and from the Percona Software Repositories).

Based on MySQL 5.5.15, including all the bug fixes in it, Percona Server 5.5.15-21.0 is now the current stable release in the 5.5 series. All of Percona’s software is open-source and free, all the details of the release can be found in the 5.5.15-21.0 milestone at Launchpad.


Improved MEMORY Storage Engine

As of MySQL 5.5.15, a Fixed Row Format (FRF) is still being used in the MEMORY storage engine. The fixed row format imposes restrictions on the type of columns as it assigns on advance a limited amount of memory per row. This renders a VARCHAR field in a CHAR field in practice, making impossible to have a TEXT or BLOB field with that engine implementation.

To overcome this limitation, the Improved MEMORY Storage Engine is introduced in this release for supporting true VARCHARVARBINARYTEXT and BLOB fields in MEMORY tables.

This implementation is based on the Dynamic Row Format (DFR) introduced by the mysql-heap-dynamic-rows patch.

DFR is used to store column values in a variable-length form, thus helping to decrease memory footprint of those columns and making possible BLOB and TEXT fields and real VARCHAR and VARBINARY.

For performance reasons, a mixed solution is implemented: the fixed format is used at the beginning of the row, while the dynamic one is used for the rest of it. All values for columns used in indexes are stored in fixed format at the first block of the row, then the following columns are handled with DRF.

More information about the usage and implementation of the Improved MEMORY Storage Engine can be found in its documentation.

More Information


Share this post

Comments (10)

  • Yuriy Vidineev

    Will this release be available in percona debain apt repository (

    August 31, 2011 at 9:32 pm
  • Chris

    Only version 5.5.13-rel20.4-136.maverick is still available from the Maverick APT Repository.

    August 31, 2011 at 10:25 pm
  • Yugene

    Waiting for 5.5.15 (or at least 5.5.14) in APT Squeeze repository, cause 5.5.13 which is currently latest available seems to have a bug in replication (described it at

    September 1, 2011 at 3:32 am
  • Rodrigo Gadea

    A last-minute bug on our apt repositories delayed the availability of the packages. It was fixed and all packages are available now in the repositories:

    Sorry for the inconvenience

    September 1, 2011 at 5:10 pm
  • Steve Jackson

    In relation to the memory storage engine improvements. I find nothing in the documentation for this patch regarding usage in temp tables… will this feature have any effect on size/performance of memory temp tables?

    September 4, 2011 at 10:51 pm
  • Laurynas Biveinis

    Steve –

    The current release changes nothing with respect to temp table handling (i.e. MyISAM is still used even if MEMORY could be used now). We are working on this, but no ETA.

    September 5, 2011 at 9:47 pm
  • Cédric


    Does the improved memory engine works with internal temporary tables ?


    September 21, 2011 at 5:44 am
    • Vadim Tkachenko


      It does not work with internal tables right now, but we may do it in future.

      September 21, 2011 at 8:14 am
  • Cédric

    Thank you Vadim for the reply. I’ve understood since I read the doc 🙂

    September 22, 2011 at 2:16 am
  • Gene Vayngrib

    Hi Laurynas, Vadim,
    Regarding the use of MEMORY engine for temp table handling when TEXT/BLOG is present. Was this problem solved?


    September 23, 2012 at 10:50 pm

Comments are closed.

Use Percona's Technical Forum to ask any follow-up questions on this blog topic.