antirez 96e0fe6232 Fix semantics of Lua calls to SELECT.
Lua scripts are executed in the context of the currently selected
database (as selected by the caller of the script).

However Lua scripts are also free to use the SELECT command in order to
affect other DBs. When SELECT is called frm Lua, the old behavior, before
this commit, was to automatically set the Lua caller selected DB to the
last DB selected by Lua. See for example the following sequence of
commands:

    SELECT 0
    SET x 10
    EVAL "redis.call('select','1')" 0
    SET x 20

Before this commit after the execution of this sequence of commands,
we'll have x=10 in DB 0, and x=20 in DB 1.

Because of the problem above, there was a bug affecting replication of
Lua scripts, because of the actual implementation of replication. It was
possible to fix the implementation of Lua scripts in order to fix the
issue, but looking closely, the bug is the consequence of the behavior
of Lua ability to set the caller's DB.

Under the old semantics, a script selecting a different DB, has no simple
ways to restore the state and select back the previously selected DB.
Moreover the script auhtor must remember that the restore is needed,
otherwise the new commands executed by the caller, will be executed in
the context of a different DB.

So this commit fixes both the replication issue, and this hard-to-use
semantics, by removing the ability of Lua, after the script execution,
to force the caller to switch to the DB selected by the Lua script.

The new behavior of the previous sequence of commadns is to just set
X=20 in DB 0. However Lua scripts are still capable of writing / reading
from different DBs if needed.

WARNING: This is a semantical change that will break programs that are
conceived to select the client selected DB via Lua scripts.

This fixes issue #1811.
2014-06-12 16:05:52 +02:00
2014-06-12 16:05:52 +02:00
2011-10-18 14:28:23 -04:00
2013-12-05 23:15:47 +05:30
2014-02-03 02:10:54 -08:00
2012-05-15 11:18:50 +02:00
2013-02-08 12:11:06 -06:00
2013-01-24 09:25:47 +11:00

Where to find complete Redis documentation?
-------------------------------------------

This README is just a fast "quick start" document. You can find more detailed
documentation at http://redis.io

Building Redis
--------------

Redis can be compiled and used on Linux, OSX, OpenBSD, NetBSD, FreeBSD.
We support big endian and little endian architectures.

It may compile on Solaris derived systems (for instance SmartOS) but our
support for this platform is "best effort" and Redis is not guaranteed to
work as well as in Linux, OSX, and *BSD there.

It is as simple as:

    % make

You can run a 32 bit Redis binary using:

    % make 32bit

After building Redis is a good idea to test it, using:

    % make test

Fixing problems building 32 bit binaries
---------

If after building Redis with a 32 bit target you need to rebuild it
with a 64 bit target, or the other way around, you need to perform a
"make distclean" in the root directory of the Redis distribution.

In case of build errors when trying to build a 32 bit binary of Redis, try
the following steps:

* Install the packages libc6-dev-i386 (also try g++-multilib).
* Try using the following command line instead of "make 32bit":

    make CFLAGS="-m32 -march=native" LDFLAGS="-m32"

Allocator
---------

Selecting a non-default memory allocator when building Redis is done by setting
the `MALLOC` environment variable. Redis is compiled and linked against libc
malloc by default, with the exception of jemalloc being the default on Linux
systems. This default was picked because jemalloc has proven to have fewer
fragmentation problems than libc malloc.

To force compiling against libc malloc, use:

    % make MALLOC=libc

To compile against jemalloc on Mac OS X systems, use:

    % make MALLOC=jemalloc

Verbose build
-------------

Redis will build with a user friendly colorized output by default.
If you want to see a more verbose output use the following:

    % make V=1

Running Redis
-------------

To run Redis with the default configuration just type:

    % cd src
    % ./redis-server
    
If you want to provide your redis.conf, you have to run it using an additional
parameter (the path of the configuration file):

    % cd src
    % ./redis-server /path/to/redis.conf

It is possible to alter the Redis configuration passing parameters directly
as options using the command line. Examples:

    % ./redis-server --port 9999 --slaveof 127.0.0.1 6379
    % ./redis-server /etc/redis/6379.conf --loglevel debug

All the options in redis.conf are also supported as options using the command
line, with exactly the same name.

Playing with Redis
------------------

You can use redis-cli to play with Redis. Start a redis-server instance,
then in another terminal try the following:

    % cd src
    % ./redis-cli
    redis> ping
    PONG
    redis> set foo bar
    OK
    redis> get foo
    "bar"
    redis> incr mycounter
    (integer) 1
    redis> incr mycounter
    (integer) 2
    redis> 

You can find the list of all the available commands here:

    http://redis.io/commands

Installing Redis
-----------------

In order to install Redis binaries into /usr/local/bin just use:

    % make install

You can use "make PREFIX=/some/other/directory install" if you wish to use a
different destination.

Make install will just install binaries in your system, but will not configure
init scripts and configuration files in the appropriate place. This is not
needed if you want just to play a bit with Redis, but if you are installing
it the proper way for a production system, we have a script doing this
for Ubuntu and Debian systems:

    % cd utils
    % ./install_server.sh

The script will ask you a few questions and will setup everything you need
to run Redis properly as a background daemon that will start again on
system reboots.

You'll be able to stop and start Redis using the script named
/etc/init.d/redis_<portnumber>, for instance /etc/init.d/redis_6379.

Code contributions
---

Note: by contributing code to the Redis project in any form, including sending
a pull request via Github, a code fragment or patch via private email or
public discussion groups, you agree to release your code under the terms
of the BSD license that you can find in the COPYING file included in the Redis
source distribution.

Please see the CONTRIBUTING file in this source distribution for more
information.

Enjoy!
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