Full-text search in ES|QL

[ChrisHegarty]

Meta issue listing tasks and subtasks for consideration as part of the Initial Search in ES|QL initiative.
Initially the features will be available only on snapshot builds.

• Add support for MATCH operator: FROM employees | WHERE title MATCH "test": @ioanatia Search in ES|QL: Add MATCH operator #110971
  • equivalent to a MATCH query
  • add tests to map failures to push to Lucene - at this stage we do not aim for graceful failures, but only to map all the failure cases through tests
• Add support for MATCH command: FROM employees | MATCH "query string": @carlosdelest
  • Initial work: ES|QL MATCH command #111147
  • Follow up work: ES|QL MATCH command - Retrieve fields information for query string #111487
  • initially this will just default to a query_string query
  • add tests to map failures to push to Lucene - the same for MATCH operator, we only need to map all failure cases through tests
• Add graceful failures for MATCH operator and command:
  • these need to happen before we make any optimizations to the logical plan - we might need a new dedicated place to add these validations, which is why this is a separate issue
• Add dataset for CSV testing for full text search
• Handle RENAME with MATCH operator Search in ES|QL: Add MATCH operator #110971 (comment)
• Investigate how to add options to support parameters for operators/commands (check with analytical engine group)
• Add support for scoring: FROM employees METADATA _score | WHERE title MATCH "test" | SORT _score @tteofili
  • adds _score as a metadata attribute
  • when _score is present it will be altered by queries such as MATCH
• Add qstr function @carlosdelest ESQL QSTR function #112590
• Add match function
• Remove match command
• ES|QL Add full-text search to the functions docs page #116024
• Examine how to lift restrictions on ES|QL full text functions (match and qstr) #115364
• ESQL: MATCH following MV_EXPAND will produce an invalid plan #115353

Enhacements:

• support for query params to accept arrays of values (maintains readability for knn)

[elasticsearchmachine]

Pinging @elastic/es-search (Team:Search)

[ioanatia]

With #110132 merged we should have the basic filtering case covered. I think it was the only piece that was missing. Let me know if there's something else needed, but I am marking that as completed.

[elasticsearchmachine]

Pinging @elastic/es-search-relevance (Team:Search Relevance)