cdb is a fast, reliable, simple package for creating and reading constant databases. The cdb database structure provides several features:

• Fast lookups: A successful lookup in a large database normally takes just two disk accesses. An unsuccessful lookup takes only one.

• Low overhead: A database uses 2048 bytes (or 4096 bytes for cdb64), plus 24 bytes per record (or 48 bytes per record for cdb64), plus the space for keys and data.

• No random limits: cdb handles any database up to 4 gigabytes (or up to an exabyte for cdb64). There are no other restrictions. Records are streamed and don't have to fit into memory. Databases are stored in a machine-independent format (one format for cdb, one format for cdb64).

• Fast atomic database replacement: cdbmake rewrites an entire database much more quickly than other hashing packages. Database replacement is safe against system crashes. Readers don't pause during a rewrite: they continue transparently using the old database until the new database is in place.

• Fast database dumps: cdbdump prints the contents of a database in cdbmake-compatible format.

Latest release: 20251021.

Author

D. J. Bernstein

More support for cdb

More packages saying that they provide tools for you to use cdb format (and in some cases cdb64 format):

• cdb64 from Pierre Carrier: Tweak of cdb-0.75 to support cdb64.

• cdb64-rs from Jiseok Choi: Rust implementation of cdb64, plus wrappers for C, Node.js, and Python.

• CDB_File: from Tim Goodwin, Matt Sergeant, and Todd Rinaldo: Perl wrapper around cdb.

• cdb-full from Kazuteru Okahashi and Rich Lane: Ruby wrapper around cdb.

• CDB::TinyCDB from Alex J. G. Burzyński: Perl wrapper around TinyCDB.

• go-cdb-1: from John Barham: Go implementation.

• go-cdb-2 from Colin Marc: Go implementation.

• go-cdb64 from Chris Lu: Go implementation of cdb64.

• howerj-cdb from Richard James Howe: C implementation.

• hs-cdb from Adam Smith: Haskell implementation.

• libowfat: C implementation from Felix von Leitner (as part of a broader library).

• luacdb from Taj Khattra: Lua wrapper around cdb.

• lua-tinycdb from A. S. Bradbury: Lua wrapper around TinyCDB.

• php-cdb: PHP implementation.

• pure-cdb from Boris Sukholitko: Haskell implementation.

• pycdb from Yusuke Shinyama: Python implementation.

• python-cdb from Mike Pomraning and Alan Grow: Python wrapper around cdb.

• python-pure-cdb from David Wilson: Python implementation. Also supports cdb64.

• rust-cdb from Bruce Guenter: Rust implementation.

• sg-cdb from Michael Alyn Miller: Java implementation.

• swift-cdb: Swift wrapper around howerj-cdb.

• TinyCDB from Michael Tokarev: C implementation.

Examples of applications using cdb format: djbdns. dnsdist. Exim. fastforward. kawipiko. krb5-strength. mess822. Postfix. qconfirm. qmail. ucspi-tcp.

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Version: This is version 2025.10.23 of the "Intro" web page.