User:PeterJAClark/Draft of Leveled (key-value datastore)
| Leveled | |
|---|---|
| Developer(s) | Martin Somner |
| Initial release | Error: df must be either "yes" or "y" (help) |
| Stable release | 0.9.24 / 1.0.4
/ August 7, 2020 / March 3, 2020 |
| Repository | https://github.com/martinsumner/leveled/ |
| Written in | Erlang |
| Type | Database library |
| License | Apache License 2.0 |
Leveled is an open-source on-disk key-value store written in Erlang by Martin Somner.[1] LevelDB is hosted on GitHub under the Apache License 2.0 and has been ported to a variety of Unix-based systems, and macOS.[2]
Features
Leveled is a simple Key-Value store based on the concept of Log-Structured Merge Trees, with the following characteristics:
- Optimised for workloads with larger values (e.g. > 4KB).
- Explicitly supports HEAD requests in addition to GET requests:
- Splits the storage of value between keys/metadata and body (assuming some definition of metadata is provided);
- Allows for the application to define what constitutes object metadata and what constitutes the body (value-part) of the object - and assign tags to objects to manage multiple object-types with different extraction rules;
- Stores keys/metadata in a merge tree and the full object in a journal of CDB files
- allowing for HEAD requests which have lower overheads than GET requests; and
- queries which traverse keys/metadatas to be supported with fewer side effects on the page cache than folds over keys/objects.
- Support for tagging of object types and the implementation of alternative store behaviour based on type.
- Allows for changes to extract specific information as metadata to be returned from HEAD requests;
- Potentially usable for objects with special retention or merge properties.
- Support for low-cost clones without locking to provide for scanning queries (e.g. secondary indexes).
- Low cost specifically where there is a need to scan across keys and metadata (not values).
- Written in Erlang as a message passing system between Actors.
Leveled is not a SQL database. Like other NoSQL and dbm stores, it does not have a relational data model and it does not support SQL queries. It has support for secondary indexes. Leveldb was developed for use as a pure-Erlang backend for the Riak, but can be used as a key-value datastore for any application in the Erlang VM.
See also
References
- ^ "Leveled Release Notes". December 07, 2018. Retrieved September 10, 2021.
{{cite web}}: Check date values in:|date=(help) - ^ "Leveled on Github". github.com. Retrieved September 10, 2021.