But how, exactly, databases use mmap?

• bolt

  22 11,201 0.0 Go

I chose bolt, a simple key/value store implemented in Go by Ben Johnson inspired by the LMDB project, for this endeavor. Mostly because of source code simplicity and my familiarity with Go language. I know a simple key/value store might not be the most complete source code for learning all the details of reading/writing data to disk, but as I have found out, it was more than enough to get a grasp of it.

• moss

  2 941 0.0 Go

  moss - a simple, fast, ordered, persistable, key-val storage library for golang (by couchbase)

  

I decided to dig through a database source code to answer that question. There are plenty of databases that use mmap. Some of them decided to not use anymore. Some examples: SQLite has an option of accessing disk content directly using memory-mapped I/O[1], it seems LevelDB used to use but it changed it[2], Lucene has an option with MMapDirectory[3], LMDB uses mmap[4], a simple key/value in-memory database from Counchbase called moss uses mmap for durability of in-memory data[5] and MongoDB removed mmap storage engine for WiredTiger[6].

• InfluxDB

  www.influxdata.com sponsored

  Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.

  

• bbolt

  18 7,617 9.1 Go

  An embedded key/value database for Go.

  

The original bolt repository is no longer maintained. A fork of bolt called bbolt is maintained and used by etcd. If you are not familiar with bolt, I recommend the articles Intro to BoltDB: Painless Performant Persistence and Bolt — an embedded key/value database for Go .

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