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Redis 2.6 release notes

Migrating from 2.4 to 2.6

Redis 2.4 is mostly a strict subset of 2.6. However there are a few things
that you should be aware of:

* You can't use .rdb and AOF files generated with 2.6 into a 2.4 instance.
* 2.6 slaves can be attached to 2.4 masters, but not the contrary, and only
  for the time needed to perform the version upgrade.

There are also a few API differences, that are unlikely to cause problems,
but it is better to keep them in mind:

* SORT now will refuse to sort in numerical mode elements that can't be parsed
  as numbers.
* EXPIREs now all have millisecond resolution (but this is very unlikely to
  break code that was not conceived exploting the previous resolution error
  in some way.)
* INFO output is a bit different now, and contains empty lines and comments
  starting with '#'. All the major clients should be already fixed to work
  with the new INFO format.

Also the following redis.conf and CONFIG GET / SET parameters changed name:

    * hash-max-zipmap-entries, now replaced by hash-max-ziplist-entries
    * hash-max-zipmap-value, now replaced by hash-max-ziplist-value
    * glueoutputbuf was no completely removed as it does not make sense


What's new in Redis 2.6.0

UPGRADE URGENCY: We suggest new users to start with 2.6.0, and old users to
                 upgrade after some testing of the application with the new
                 Redis version.

* Server side Lua scripting, see
* Virtual Memory removed (was deprecated in 2.4)
* Hardcoded limits about max number of clients removed.
* AOF low level semantics is generally more sane, and especially when used
  in slaves.
* Milliseconds resolution expires, also added new commands with milliseconds
  precision (PEXPIRE, PTTL, ...).
* Clinets max output buffer soft and hard limits. You can specifiy different
  limits for different classes of clients (normal,pubsub,slave).
* AOF is now able to rewrite aggregate data types using variadic commands,
  often producing an AOF that is faster to save, load, and is smaller in size.
* Every redis.conf directive is now accepted as a command line option for the
  redis-server binary, with the same name and number of arguments.
* Hash table seed randomization for protection against collisions attacks.
* Performances improved when writing large objects to Redis.
* Significant parts of the core refactored or rewritten. New internal APIs
  and core changes allowed to develop Redis Cluster on top of the new code,
  however for 2.6 all the cluster code was removed, and will be released with
  Redis 3.0 when it is more complete and stable.
* Redis ASCII art logo added at startup.
* Crash report on memory violation or failed asserts improved significantly
  to make debugging of hard to catch bugs simpler.
* redis-benchmark improvements: ability to run selected tests,
  CSV output, faster, better help.
* redis-cli improvements: --eval for comfortable development of Lua scripts.
* SHUTDOWN now supports two optional arguments: "SAVE" and "NOSAVE".
* INFO output split into sections, the command is now able to just show 
  pecific sections.
* New statistics about how many time a command was called, and how much
  execution time it used (INFO commandstats).
* More predictable SORT behavior in edge cases.


Credits: Where not specified the implementation and design are done by
Salvatore Sanfilippo and Pieter Noordhuis. Thanks to VMware for making all
this possible. Also many thanks to all the other contributors and the amazing
community we have.

See commit messages for more credits.