User:PeterJAClark/Draft of Leveled (key-value datastore)
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| Developer(s) | Martin Sumner |
|---|---|
| Initial release | 11 May 2019 |
| Stable release | 0.9.24 / 1.0.4
/ August 7, 2021 / March 3, 2021 |
| 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 Sumner.[1] Leveled is hosted on GitHub under the Apache License 2.0 and has been ported to a variety of Unix-based systems, and macOS.[2] Leveled is intended to be used as a Key-Value store within applications running on the BEAM virtual machine, and is primarily used on the Riak database.
Features[edit]
Leveled is a simple Key-Value store based on the concept of Log-Structured Merge Trees, with the following characteristics[1]:
- 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. Leveled 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[edit]
References[edit]
- ^ a b "Leveled Release Notes". December 7, 2018. Retrieved September 10, 2021.
- ^ "Leveled on Github". github.com. Retrieved September 10, 2021.
External links[edit]
Category:2018 software Category:Bigtable implementations Category:Erlang libraries Category:Key-value databases Category:NoSQL Category:Database engines Category:Embedded databases Category:Software using the Apache 2.0 license