The Apache CouchDB development community is proud to announce the immediate availability of version 2.2.

Version 2.2 incorporates 8 months of improvements to the already successful 2.1 release series.

For CouchDB < 2.0 users, the main improvements in 2.0 still apply for 2.2:

  • 99% API compatibility- native clustering for increased performance, data redundancy, and ability to scale
  • Easy querying with Mango
  • New Admin interface- Major performance improvements around compaction and replication.

Most importantly, CouchDB 2.0 finally fulfils CouchDB’s original vision of a distributed and clustered document database.

The 2018 Annual CouchDB User Survey has revealed that as of July 2019 98% of our user-base have adopted CouchDB 2.x with about 50% running CouchDB 1.x at the same time.

Note, as previously announced on the developer mailing list, there will be no further releases of CouchDB 1.x. CouchDB 1.x is a fine piece of software and folks with existing installations should be fine continuing to use it, just beware that there won’t be any further bug fixes or security fixes coming. This reflects project reality insofar as that the 1.x line has only received minimal maintenance in the past few years with the majority of the effort going to 2.x.

2.2 Highlights

See the official release notes document for an exhaustive list of all changes.

  • New pluggable storage engine framework. This internal refactor makes it possible for CouchDB to use different backends for storing the base database file itself. The refactor included a full migration of the existing “legacy” storage engine into the new framework
  • The minimum supported version of Erlang is now R17, not 16B03. Support for Erlang 21 is still ongoing and will be provided in a future release.
  • The CouchDB replicator can now make use of the /_session endpoint rather than relying entirely on HTTP basic authentication headers. This can greatly improve replication performance.
  • CouchDB no longer fails to complete replicating databases with large attachments. The fix for this issue included several related changes (GitHub issue 745 et.al.)
  • Multiple queries can now be made at the POST /{db}/_all_docs/queries, POST /{db}/_design_docs/queries and POST /{db}/_local_docs/queries endpoints. Also, a new endpoint POST /{db}/_design/{ddoc}/_view/{view}/queries
  • The least recently used (LRU) cache of databases is now only updated on database write, not read. This has lead to significant performance enhancements on very busy clusters.
  • The revision stemming algorithm was optimized down from O(N^2) to O(N) via a depth-first search approach, and then further improved by calling the stemming operation only when necessary.
  • CouchDB now checks for request authorization only once per each database request, improving the performance of any request that requires authorization.
  • If a user specifies a value for use_index that is not valid for the selector (does not meet coverage requirements or proper sort fields), attempt to fall back to a valid index or full DB scan rather than returning a 400.
  • CouchDB now includes a new builtin reduce function_approx_count_distinct, that uses a HyperLogLog algorithm to estimate the number of distinct keys in the view index. The precision is currently fixed to 2^11 observables, and therefore uses approximately 1.5KB of memory.
  • Much improved documentation. Highlights include:

    • A complete rewrite of the sharding documentation.
    • Developer installation notes (INSTALL.*.rst)
    • Much of the content of the original CouchDB Wiki has been imported into the official docs. (The old CouchDB Wiki is in the process of being deprecated.)


  • Much improved Fauxton functionality. Highlights include:

    • Search support in the code editor
    • Support for relative Fauxton URLs (i.e., not always at /_utils)
    • Replication setup enhancements for various authentication mechanisms
    • Fixes for IE10, IE11, and Edge (we hope…)
    • Resolving conflicts of design documents is now allowed


  • Many more smaller bug fixes and performance improvements, as well as more features and refinements. See the release notes for a full list.


One thought on “2.2

  1. CouchDB Weekly News, August 9, 2018 – CouchDB Blog

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