https://github.com/crystal-community/leveldb

Crystal binding for LevelDB
https://github.com/crystal-community/leveldb

crystal leveldb

Last synced: 10 days ago
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Crystal binding for LevelDB

• Host: GitHub
• URL: https://github.com/crystal-community/leveldb
• Owner: crystal-community
• License: lgpl-3.0
• Created: 2016-07-09T18:04:25.000Z (over 8 years ago)
• Default Branch: master
• Last Pushed: 2020-03-06T18:09:49.000Z (almost 5 years ago)
• Last Synced: 2024-10-30T16:41:34.595Z (about 1 month ago)
• Topics: crystal, leveldb
• Language: Crystal
• Size: 55.7 KB
• Stars: 39
• Watchers: 7
• Forks: 5
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md

Awesome Lists containing this project

• awesome-crystal - leveldb - Crystal bindings for LevelDB (Database Drivers/Clients)
• awesome-crystal - leveldb - Crystal bindings for LevelDB (Database Drivers/Clients)
• awesome-crystal - leveldb - Crystal bindings for LevelDB (Database Drivers/Clients)

README

        
# LevelDB 

Crystal binding for [LevelDB](https://github.com/google/leveldb).

[![Build Status](https://travis-ci.org/crystal-community/leveldb.svg?branch=master)](https://travis-ci.org/crystal-community/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:

```

sudo apt-get install libleveldb-dev libleveldb1v5 libsnappy1v5

```

### shard.yml

```yaml

dependencies:

  leveldb:

    github: "crystal-community/leveldb"

    version: "~> 0.2.0"

```

## Usage

### Basic usage

```crystal

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

```

### Batches 

> Apply a atomic batch of of operation to the key-value store.

```crystal

require "leveldb"

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

begin

  batch = LevelDB::Batch.new

  batch.put("name","Martin")

  batch.put("age","25")

  batch.put("location","Bariloche")

  batch.delete("age")

  # write batch to the db in atomic way

  db.write(batch)

  puts db.get("name")

  puts db.get("age") # nil

  puts db.get("location")

ensure

  # free memory 

  batch.destroy 

  # close the database

  db.close

end

```

### Snapshots

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

```crystal

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

```

## Performance

There is performance comparison of LevelDB and other stores from

[Kiwi](https://github.com/greyblake/crystal-kiwi#performance-porn) project.

![LevelDB VS other storages](https://sc-cdn.scaleengine.net/i/8a5361ab85b005f7bfb6ed7941b4a5ef.jpg)

## Contributors

- [greyblake](https://github.com/greyblake) Sergey Potapov - creator, maintainer

- [twisterghost](https://github.com/twisterghost) Michael Barrett