Basic Lua scripting is supported by the IServer.ScriptLoad(Async), IServer.ScriptExists(Async), IServer.ScriptFlush(Async), IDatabase.ScriptEvaluate, and IDatabaseAsync.ScriptEvaluateAsync methods.
These methods expose the basic commands necessary to submit and execute Lua scripts to redis.
More sophisticated scripting is available through the LuaScript class. The LuaScript class makes it simpler to prepare and submit parameters along with a script, as well as allowing you to use cleaner variables names.
An example use of the LuaScript:
const string Script = "redis.call('set', @key, @value)";
using (ConnectionMultiplexer conn = /* init code */)
{
var db = conn.GetDatabase(0);
var prepared = LuaScript.Prepare(Script);
db.ScriptEvaluate(prepared, new { key = (RedisKey)"mykey", value = 123 });
}
The LuaScript class rewrites variables in scripts of the form @myVar into the appropriate ARGV[someIndex] required by redis. If the
parameter passed is of type RedisKey it will be sent as part of the KEYS collection automatically.
Any object that exposes field or property members with the same name as @-prefixed variables in the Lua script can be used as a parameter hash to
Evaluate calls. Supported member types are the following:
StackExchange.Redis handles Lua script caching internally. It automatically transmits the Lua script to redis on the first call to ‘ScriptEvaluate’. For further calls of the same script only the hash with EVALSHA is used.
For more control of the Lua script transmission to redis, LuaScript objects can be converted into LoadedLuaScripts via LuaScript.Load(IServer).
LoadedLuaScripts are evaluated with the EVALSHA, and referred to by hash.
An example use of LoadedLuaScript:
const string Script = "redis.call('set', @key, @value)";
using (ConnectionMultiplexer conn = /* init code */)
{
var db = conn.GetDatabase(0);
var server = conn.GetServer(/* appropriate parameters*/);
var prepared = LuaScript.Prepare(Script);
var loaded = prepared.Load(server);
loaded.Evaluate(db, new { key = (RedisKey)"mykey", value = 123 });
}
All methods on both LuaScript and LoadedLuaScript have Async alternatives, and expose the actual script submitted to redis as the ExecutableScript property.