LevelDB

Crystal binding for LevelDB.

LevelDB is a fast key-value storage library written at Google that provides an ordered mapping from string keys to string values.

Installation

Prerequisites

Debian:

apt-get install libleveldb-dev libleveldb1 libsnappy1

shard.yml

dependencies:
  leveldb:
    github: "greyblake/crystal-leveldb"
    version: "~> 0.1.0"

Usage

Basic usage

require "leveldb"

# Create DB (if does not exist yet) and open
db = LevelDB::DB.new("./db")

# Put, get, delete
db.put("name", "Sergey")
db.get("name")  # => "Sergey"
db.delete("name")
db.get("name")  # => nil

# [], []= methods work the same
db["city"] = "Berlin"
db["city"]  # => "Berlin"

# Iterate through all the keys
db.each do |key, val|
  puts "#{key} = #{val}"
end

# Close database
db.close
db.closed? # => true
db.opened? # => false

# Close the database and remove all the data
db.destroy

# Remove all the keys, keep the database open
db.clear

Snapshots

Snapshots provide consistent read-only views over the entire state of the key-value store.

db = LevelDB::DB.new("./db")

db.put("a", "1")
db.get("a")  # => "1"

snapshot = db.create_snapshot
db.delete("a")
db.get("a")  # => nil

db.set_snapshot(snapshot)
db.get("a")  # => "1"

db.unset_snapshot
db.get("a")  # => nil

Contributors

• greyblake Sergey Potapov - creator, maintainer