Question

I’m currently developing a cache that needs increase a few hundred counters for every call like this:

redis.pipelined do
  keys.each{ |key| redis.incr key }
end

In my profiling now I saw that the replies I don’t need are still collected by the redis gem and waste some valueable time. Can I tell redis in some way that I’m not interested in the replies? Is there a better way to increment lots of values.

I didn’t find a MINCR command, for example..

Thanks in advance!

Answer 1

Yes… in 2.6, at least. You could do this in a LUA script, and simply have the LUA script return an empty result. Here it is using the booksleeve client:

const int DB = 0; // any database number
// prime some initial values
conn.Keys.Remove(DB, new[] {"a", "b", "c"});
conn.Strings.Increment(DB, "b");
conn.Strings.Increment(DB, "c");
conn.Strings.Increment(DB, "c");

// run the script, passing "a", "b", "c", "c" to
// increment a & b by 1, c twice
var result = conn.Scripting.Eval(DB,
    @"for i,key in ipairs(KEYS) do redis.call('incr', key) end",
    new[] { "a", "b", "c", "c"}, // <== aka "KEYS" in the script
    null); // <== aka "ARGV" in the script

// check the incremented values
var a = conn.Strings.GetInt64(DB, "a");
var b = conn.Strings.GetInt64(DB, "b");
var c = conn.Strings.GetInt64(DB, "c");

Assert.IsNull(conn.Wait(result), "result");
Assert.AreEqual(1, conn.Wait(a), "a");
Assert.AreEqual(2, conn.Wait(b), "b");
Assert.AreEqual(4, conn.Wait(c), "c");

Or to do the same thing with incrby, passing the “by” numbers as arguments, change the middle portion to:

// run the script, passing "a", "b", "c" and 1, 1, 2
// increment a & b by 1, c twice
var result = conn.Scripting.Eval(DB,
    @"for i,key in ipairs(KEYS) do redis.call('incrby', key, ARGV[i]) end",
    new[] { "a", "b", "c" }, // <== aka "KEYS" in the script
    new object[] { 1, 1, 2 }); // <== aka "ARGV" in the script