leveldb

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

> **This repository is receiving very limited maintenance. We will only review the following types of changes.**
>
> * Fixes for critical bugs, such as data loss or memory corruption
> * Changes absolutely needed by internally supported leveldb clients. These typically fix breakage introduced by a language/standard library/OS update

[![ci](https://github.com/google/leveldb/actions/workflows/build.yml/badge.svg)](https://github.com/google/leveldb/actions/workflows/build.yml)

Authors: Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)

# Features

  * Keys and values are arbitrary byte arrays.
  * Data is stored sorted by key.
  * Callers can provide a custom comparison function to override the sort order.
  * The basic operations are `Put(key,value)`, `Get(key)`, `Delete(key)`.
  * Multiple changes can be made in one atomic batch.
  * Users can create a transient snapshot to get a consistent view of data.
  * Forward and backward iteration is supported over the data.
  * Data is automatically compressed using the [Snappy compression library](https://google.github.io/snappy/), but [Zstd compression](https://facebook.github.io/zstd/) is also supported.
  * External activity (file system operations etc.) is relayed through a virtual interface so users can customize the operating system interactions.

# Documentation

  [LevelDB library documentation](https://github.com/google/leveldb/blob/main/doc/index.md) is online and bundled with the source code.

# Limitations

  * This is not a SQL database.  It does not have a relational data model, it does not support SQL queries, and it has no support for indexes.
  * Only a single process (possibly multi-threaded) can access a particular database at a time.
  * There is no client-server support builtin to the library.  An application that needs such support will have to wrap their own server around the library.

# Getting the Source

```bash
git clone --recurse-submodules https://github.com/google/leveldb.git
```

# Building

This project supports [CMake](https://cmake.org/) out of the box.

### Build for POSIX

Quick start:

```bash
mkdir -p build && cd build
cmake -DCMAKE_BUILD_TYPE=Release .. && cmake --build .
```

### Building for Windows

First generate the Visual Studio 2017 project/solution files:

```cmd
mkdir build
cd build
cmake -G "Visual Studio 15" ..
```
The default default will build for x86. For 64-bit run:

```cmd
cmake -G "Visual Studio 15 Win64" ..
```

To compile the Windows solution from the command-line:

```cmd
devenv /build Debug leveldb.sln
```

or open leveldb.sln in Visual Studio and build from within.

Please see the CMake documentation and `CMakeLists.txt` for more advanced usage.

# Contributing to the leveldb Project

> **This repository is receiving very limited maintenance. We will only review the following types of changes.**