We will want to use Apache Lucene 9 once it has been released in the elasticsearch 8.x line. This meta issue tracks updates that we need to make to our master branch in order to integrate this new release.

Snapshot upgrade PR: #73324

The following issues need to be addressed prior to merging the upgrade to Lucene 9, some of which may require deprecations in 7x:

• CuckooFilter uses the PackedInts.Mutable class which is no longer available in lucene 9 (@iverase) Remove Lucene's PackedInt dependency from Cuckoo filter #74736
• SimpleFSDirectory is no longer available, so should be deprecated in 7.x (@dnhatn) Deprecate SimpleFS and replace it with NIOFS #75156
• SegmentStats reports RAM accounting information which is no longer available (@jpountz) Remove RAM accounting from segments #75274
• Analyzer.version has been removed (@romseygeek) Deprecate setting version on analyzers #74073
• SpanBoostQuery has been removed (@romseygeek) Remove references to SpanBoostQuery #74432
• Migration of indices.query.bool.max_clause_count wich is now for the entire query tree rather than per BooleanQuery. indices.query.bool.max_clause_count now limits all query clauses #75297

The following issues will need to be addressed after upgrading to Lucene 9:

• Add support for vectors to the disk usage API. (8.x @jtibshirani)
• Add support for vectors to the field usage API. (8.x @ywelsch) Add field usage support for vectors #80608
• Remove verbose option from index segments stats Remove index segments 'verbose' option #75955 (@romseygeek)
• KeystoreWrapper should avoid using endianness utils for writing Don't use endianness reverse util for writing KeyStore file #78304
• MetadataStateFormat should avoid using endianness utils for writing Don't use endianness reverse util for writing metadata state file #78309
• Deprecate and remove max_merge_at_once_explicit (Deprecate setting max_merge_at_once_explicit #80574) (8.0 @dnhatn)
• Expose norwegiannormalization, swedishminimalstem, swedishminimalstem, telugustem, japanese_completion (8.x @romseygeek)
• Sort optimizations: see TODO: IndexNumericFieldData and NumberFieldTypeTests#testIndexSortIntRange (8.x @mayya-sharipova)
• Review permission in server/src/main/resources/org/elasticsearch/bootstrap/security.policy Remove server jar accessDeclaredMembers permission #78431
• IndexSearcher max clause count #46433 (8.0 @romseygeek)