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10
JAN
2010

Tokyo Cabinet's Key-Value Database Types

We've taken a good look at Tokyo Cabinet's Hash Database, but there's a lot more to the library than just that. Tokyo Cabinet supports three other kinds of databases. In addition, each database type accepts various tuning parameters that can be used to change its behavior. Each database type and setting involves different tradeoffs so you really have a lot of options for turning Tokyo Cabinet into exactly what you need. Let's look into some of those options now.

The B+Tree Database

Tokyo Cabinet's B+Tree Database is a little slower than the Hash Database we looked at before. That's its downside. However, giving up a little speed gains you several extra features that may just allow you to work smarter instead of faster.

The B+Tree Database is a more advanced form of the Hash Database. What that means is that all of the stuff I showed you in the last article still applies. You can set, read, and remove values by keys, iteration is supported, and you still have access to the neat options like adding to counters. With a B+Tree Database you get all of that and more.
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In: Key-Value Stores | Tags: Tokyo Cabinet | 4 Comments

1

JAN
2010

Tokyo Cabinet as a Key-Value Store

Like most key-value stores, Tokyo Cabinet has a very Hash-like interface from Ruby (assuming you use Oklahoma Mixer). You can almost think of a Tokyo Cabinet database as a Hash that just happens to be stored in a file instead of memory. The advantage of that is that your data doesn't have to fit into memory. Luckily, you don't have to pay a big speed penalty to get this disk-backed storage. Tokyo Cabinet is pretty darn fast.

Getting and Setting Keys

Let's have a look at the normal Hash-like methods as well as the file storage aspect:

#!/usr/bin/env ruby -KU

require "oklahoma_mixer"

OklahomaMixer.open("data.tch") do |db|
  if db.size.zero?
    puts "Loading the database.  Rerun to read back the data."
    db[:one] = 1
    db[:two] = 2
    db.update(:three => 3, :four => 4)
    db["users:1"] = "James"
    db["users:2"] = "Ruby"
  else
    puts "Reading data."
    %w[ db[:one]
        db["users:2"]
        -
        db.keys
        db.keys(:prefix\ =>\ "users:")
        db.keys(:limit\ =>\ 2)
        db.values
        -
        db.values_at(:one,\ :two) ].each do |command|
      puts(command == "-" ? "" : "#{command} = %p" % [eval(command)])
    end
  end
end