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The motivation for this new commands is to be search in the usage of Redis for real time statistics. See the article "Fast real time metrics using Redis". http://blog.getspool.com/2011/11/29/fast-easy-realtime-metrics-using-redis-bitmaps/ In general Redis strings when used as bitmaps using the SETBIT/GETBIT command provide a very space-efficient and fast way to store statistics. For instance in a web application with users, every user can be associated with a key that shows every day in which the user visited the web service. This information can be really valuable to extract user behaviour information. With Redis bitmaps doing this is very simple just saying that a given day is 0 (the data the service was put online) and all the next days are 1, 2, 3, and so forth. So with SETBIT it is possible to set the bit corresponding to the current day every time the user visits the site. It is possible to take the count of the bit sets on the run, this is extremely easy using a Lua script. However a fast bit count native operation can be useful, especially if it can operate on ranges, or when the string is small like in the case of days (even if you consider many years it is still extremely little data). For this reason BITOP was introduced. The command counts the number of bits set to 1 in a string, with optional range: BITCOUNT key [start end] The start/end parameters are similar to GETRANGE. If omitted the whole string is tested. Population counting is more useful when bit-level operations like AND, OR and XOR are avaialble. For instance I can test multiple users to see the number of days three users visited the site at the same time. To do this we can take the AND of all the bitmaps, and then count the set bits. For this reason the BITOP command was introduced: BITOP [AND|OR|XOR|NOT] dest_key src_key1 src_key2 src_key3 ... src_keyN In the special case of NOT (that inverts the bits) only one source key can be passed. The judicious use of BITCOUNT and BITOP combined can lead to interesting use cases with very space efficient representation of data. The implementation provided is still not tested and optimized for speed, next commits will introduce unit tests. Later the implementation will be profiled to see if it is possible to gain an important amount of speed without making the code much more complex. |
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Makefile | ||
MANIFESTO | ||
README | ||
redis.conf | ||
runtest |
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 NOTE: if after building Redis with a 32 bit target you need to rebuild it with a 64 bit target you need to perform a "make clean" in the root directory of the Redis distribution. 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 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. Enjoy!