LevelDB is an open source, fast, key-value storage library written by Google that provides an ordered mapping from string keys to string values. Leveldb is based on LSM (Log-Structured Merge-Tree) and uses SSTable and MemTable for the database implementation.
LevelDB stores keys and values in arbitrary byte arrays, and data is sorted by key. It supports batching writes, forward and backward iteration, and compression of the data via Google’s Snappy compression library.
LevelDB uses Google Snappy data compression by default. This means more CPU usage but less disk space. LevelDB is a C++ library that can be used in many contexts. For example, LevelDB may be used by a web browser to store a cache of recently accessed web pages, or by an operating system to store the list of installed packages and package dependencies, or by an application to store user preference settings.
- 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.
- External activity (file system operations etc.) is relayed through a virtual interface so users can customize the operating system interactions.
Developer: Jeffrey Dean, Sanjay Ghemawat
License: New BSD License
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