compl1.rb

# compl1.rb - Redis autocomplete example
# download female-names.txt from http://antirez.com/misc/female-names.txt

require 'rubygems'
require 'redis'

r = Redis.new

# Create the completion sorted set
if !r.exists(:compl)
    puts "Loading entries in the Redis DB\n"
    File.new('female-names.txt').each_line{|n|
        n.strip!
        (1..(n.length)).each{|l|
            prefix = n[0...l]
            r.zadd(:compl,0,prefix)
        }
        r.zadd(:compl,0,n+"*")
    }
else
    puts "NOT loading entries, there is already a 'compl' key\n"
end

# Complete the string "mar"

def complete(r,prefix,count)
    results = []
    rangelen = 50 # This is not random, try to get replies < MTU size
    start = r.zrank(:compl,prefix)
    return [] if !start
    while results.length != count
        range = r.zrange(:compl,start,start+rangelen-1)
        start += rangelen
        break if !range or range.length == 0
        range.each {|entry|
            minlen = [entry.length,prefix.length].min
            if entry[0...minlen] != prefix[0...minlen]
                count = results.count
                break
            end
            if entry[-1..-1] == "*" and results.length != count
                results << entry[0...-1]
            end
        }
    end
    return results
end

complete(r,"marcell",50).each{|res|
    puts res
}

Started to extract and cleanup a bit: http://github.com/djanowski/replete

Quick line-by-line (ish) port to Python: http://gist.github.com/577852

What is the advantage over loading the entries in memory (as a ruby constant) and use that constant for autocompletion? Assuming redis will hold the entries in memory.