mirrors
/
elasticsearch
mirror of https://mirror.osredm.com/root/elasticsearch.git
2
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

ESQL: Improve LOOKUP JOIN page (#125688) (#125798) 

Forward port of #125688
This commit is contained in:
Alexander Spies 2025-03-28 09:07:28 +01:00 committed by GitHub
parent 7eb865473e
commit ea98166919
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
1 changed files with 5 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
docs/reference/query-languages/esql/esql-lookup-join.md
View File

@ -42,7 +42,7 @@ The `LOOKUP JOIN` command adds new columns to a table, with data from {{es}} ind
## Example
`LOOKUP JOIN` has left-join behavior. If no rows match in the looked index, `LOOKUP JOIN` retains the incoming row and adds `null`s. If many rows in the lookedup index match, `LOOKUP JOIN` adds one row per match.
`LOOKUP JOIN` has left-join behavior. If no rows match in the lookup index, `LOOKUP JOIN` retains the incoming row and adds `null`s. If many rows in the lookup index match, `LOOKUP JOIN` adds one row per match.
In this example, we have two sample tables:
@ -112,7 +112,9 @@ To use `LOOKUP JOIN`, the following requirements must be met:
* Numeric types follow these compatibility rules:
* `short` and `byte` are compatible with `integer` (all represented as `int`)
* `float`, `half_float`, and `scaled_float` are compatible with `double` (all represented as `double`)
* For text fields: You can use text fields on the left-hand side of the join only if they have a `.keyword` subfield
* For text fields: You can only use text fields as the join key on the left-hand side of the join and only if they have a `.keyword` subfield
To obtain a join key with a compatible type, use a [conversion function](/reference/query-languages/esql/esql-functions-operators.md#esql-type-conversion-functions) if needed.
For a complete list of supported data types and their internal representations, see the [Supported Field Types documentation](/reference/query-languages/esql/limitations.md#_supported_types).
@ -121,7 +123,7 @@ For a complete list of supported data types and their internal representations,
The following are the current limitations with `LOOKUP JOIN`
* Indices in [lookup](/reference/elasticsearch/index-settings/index-modules.md#index-mode-setting) mode are always single-sharded.
* Cross cluster search is unsupported. Both source and lookup indices must be local.
* Cross cluster search is unsupported initially. Both source and lookup indices must be local.
* Currently, only matching on equality is supported.
* `LOOKUP JOIN` can only use a single match field and a single index. Wildcards, aliases, datemath, and datastreams are not supported.
* The name of the match field in `LOOKUP JOIN lu_idx ON match_field` must match an existing field in the query. This may require `RENAME`s or `EVAL`s to achieve.