Zammad 6.5 – Search Index Fails on Elasticsearch OSS 7.10.2 Due to flattened Field Type

Technical assistance
1

Infos:

  • Used Zammad version: 6.5.0
  • Used Zammad installation type: (source, package, docker-compose, …) package (APT on Ubuntu 22.04)
  • Operating system: Ubuntu 22.04 LTS
  • Browser + version: Firefox 126 / Chrome 126 (any modern browser – N/A for issue)

Expected behavior:

  • Zammad should rebuild the search index successfully using Elasticsearch OSS 7.10.2, as it falls within the supported version range (>= 7.8, < 9) listed in the documentation.

Actual behavior:

  • Running zammad run rake zammad:searchindex:rebuild fails with:
  • No handler for type [flattened] declared on field [preferences]

Full error indicates:

  • mapper_parsing_exception
  • Elasticsearch OSS 7.10.2 does not support flattened field type

Steps to reproduce the behavior:

    • Install Zammad via APT (apt install zammad) on Ubuntu 22.04
  • Use Elasticsearch OSS 7.10.2 as the search backend (default port 9200)
  • Upgrade to Zammad 6.5
  • Run:
    zammad run rake zammad:searchindex:rebuild

Additional Notes:

Zammad’s documentation states support for Elasticsearch >= 7.8, but does not clarify that flattened requires either:

  • OpenSearch 2.5+, or
  • Official (non-OSS) Elasticsearch builds

This leads to unexpected failures for users running OSS 7.10.2 — which was the only free version after Elastic changed its license.

Would be great to:

  • Clarify OSS vs official build compatibility in docs
  • Warn about flattened dependency in upgrade notes
  • Consider making flattened optional/fallback to object

Thanks!

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