leveldb-rubyでRubyからLevelDBを使う

gem "leveldb-ruby"

require 'leveldb'

db = LevelDB::DB.new('leveldb_data')

# Hash風に読み書き
p db['foo'] = 'bar' #=> 'bar'
p db['foo'] #=> 'bar'

# deleteで削除
p db.delete('foo') #=> 'bar'
p db.delete('foo') #=> nil

# put, getを使った読み書き
p db.put('foo', 'bar') #=> 'bar'
p db.get('foo') #=> 'bar'

# バイナリのキーや値を扱える
require 'securerandom'

p bin_key = SecureRandom.random_bytes #=> "O\xF3\xA6\xD9\x966F|\xC0\xFC2\tFe}\x9E"
p bin_val = SecureRandom.random_bytes #=> "\x19\xE0\x92\x8Bs\xAE\xC1\xF2d\xCE\xBE\xE1\xD8i0\xBC"

p db[bin_key] = bin_val #=> "\x19\xE0\x92\x8Bs\xAE\xC1\xF2d\xCE\xBE\xE1\xD8i0\xBC"
p db[bin_key] #=> "\x19\xE0\x92\x8Bs\xAE\xC1\xF2d\xCE\xBE\xE1\xD8i0\xBC"

require 'leveldb'

db = LevelDB::DB.new('leveldb_data')

# LevelDB::DBで利用できるメソッド
p db.methods #=> [:get, :close!, :iterator, :close, :keys, :delete, :member?, :inspect, :exists?, :[], :[]=, :contains?, :includes?, :put, :size, :each, :batch, :pathname, :options, :values, :chain, :to_set, :lazy, :to_h, :include?, :max, :min, :find, :to_a, :entries, :sort, :sort_by, :grep, :grep_v, :count, :detect, :find_index, :find_all, :select, :filter, :reject, :collect, :map, :flat_map, :collect_concat, :inject, :reduce, :partition, :group_by, :first, :all?, :any?, :one?, :none?, :minmax, :min_by, :max_by, :minmax_by, :each_with_index, :reverse_each, :each_entry, :each_slice, :each_cons, :each_with_object, :zip, :take, :take_while, :drop, :drop_while, :cycle, :chunk, :slice_before, :slice_after, :slice_when, :chunk_while, :sum, :uniq, :instance_variable_defined?, :remove_instance_variable, :instance_of?, :kind_of?, :is_a?, :tap, :instance_variable_set, :protected_methods, :instance_variables, :instance_variable_get, :private_methods, :public_methods, :public_send, :method, :public_method, :singleton_method, :define_singleton_method, :extend, :to_enum, :enum_for, :<=>, :===, :=~, :!~, :eql?, :respond_to?, :gem, :freeze, :object_id, :send, :to_s, :display, :nil?, :hash, :class, :singleton_class, :clone, :dup, :itself, :yield_self, :then, :taint, :tainted?, :untaint, :untrust, :untrusted?, :trust, :frozen?, :methods, :singleton_methods, :equal?, :!, :==, :instance_exec, :!=, :instance_eval, :__id__, :__send__]

# HashにあってLevelDB::DBにないメソッド
p ({}.methods - db.methods) #=> [:index, :<=, :replace, :clear, :>=, :empty?, :fetch, :shift, :select!, :length, :values_at, :filter!, :delete_if, :reject!, :keep_if, :assoc, :rassoc, :compact, :flatten, :>, :compact!, :to_hash, :to_proc, :<, :default, :rehash, :store, :default=, :default_proc, :default_proc=, :each_value, :each_key, :each_pair, :transform_keys, :transform_keys!, :transform_values, :transform_values!, :fetch_values, :update, :slice, :merge!, :invert, :has_key?, :has_value?, :merge, :key?, :value?, :compare_by_identity, :compare_by_identity?, :dig, :key]

require 'leveldb'

db = LevelDB::DB.new('leveldb_data')

db['001'] = 'a'
db['002'] = 'b'
db['003'] = 'c'
db['004'] = 'd'
db['005'] = 'e'

db.each(from: '002', to: '004') do |k, v|
  p k, v #=> "002" "b" "003" "c" "004" "d"
end

db = LevelDB::DB.new 'leveldb_data', compression: LevelDB::CompressionType::NoCompression
p db.options #=> #<LevelDB::Options:0x0000556b63952c60 @create_if_missing=true, @error_if_exists=false, @paranoid_checks=false, @write_buffer_size=4194304, @max_open_files=1000, @block_size=4096, @block_restart_interval=16, @compression=LevelDB::CompressionType::NoCompression>

# read.rb
require 'leveldb'
require 'benchmark'

db = LevelDB::DB.new('leveldb_data')

Benchmark.bm do |x|
  x.report "Read" do
    10_000_000.times do |i|
      k = "%016d" % i

      db[k]
    end
  end
end

# write.rb
require 'leveldb'
require 'benchmark'

db = LevelDB::DB.new('leveldb_data')

Benchmark.bm do |x|
  x.report "Write" do
    10_000_000.times do |i|
      k = v = "%016d" % i

      db[k] = v
    end
  end
end