[8.x] Initial support for TEXT fields in LOOKUP JOIN condition (#119473) #120732
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) When the join field on the right hand-side is a TEXT field, we cannot do an exact match. Since ES|QL treats TEXT fields as KEYWORD in all cases, ideally we would like to do the same for JOIN. However, this is achieved on the left-hand index in a way that is not easily achievable on the right-hand side. Comparing filtering and field extraction of left and right: * `FROM left` * FieldExtraction is done using `field.keyword` subfield if it exists, or from `_source` otherwise * Filtering is done by pushing down to Lucene `field.keyword` if it exists, or by not pushing down and filtering the value extracted from `_source` inside the compute engine itself * `LOOKUP JOIN right` * FieldExtraction is done simplistically, with no `_source` extraction * Filtering pushdown can be done with `field.keyword` if it exists, but we have no easy solution to filtering otherwise The decision taken is to disallow joining on TEXT fields, but allow explicit joining on the underlying keyword field (explicit in the query): | left type | right type | result | | --- | --- | --- | | KEYWORD | KEYWORD | ✅ Works | | TEXT | KEYWORD | ✅ Works | | KEYWORD | TEXT | ❌ Type mismatch error | | TEXT | TEXT | ❌ Type mismatch error | ``` FROM test | LOOKUP JOIN `test-lookup` ON color.keyword ``` ``` FROM test | RENAME color AS x | EVAL color.keyword = x | LOOKUP JOIN `test-lookup` ON color.keyword ``` ``` FROM test | EVAL color = color.keyword | LOOKUP JOIN `test-lookup` ON color ``` ``` FROM test | LOOKUP JOIN `test-lookup` ON color ```
craigtaverner added backport Team:Analytics craigtaverner added the auto-merge-without-approval 
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This is a manual backport of #119473