opensearch-project / opensearch-project/sql
[BUG] Make return type inferrable for TRANSFORM and other lambda functions
@yuancu is already working on this.
Since Dec 22, 2025.
- Dominant language
- Java
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- 43
Description
Query Information
PPL Command/Query:
source=people | eval array = array(1, -2, 3), result = transform(array, x -> x + 2) | fields result
Expected Result:
[3,0,5] of type INTEGER ARRAY
Actual Result:
[3,0,5] of type ANY ARRAY
Dataset Information
Dataset/Schema Type
- OpenTelemetry (OTEL)
- Simple Schema for Observability (SS4O)
- Open Cybersecurity Schema Framework (OCSF)
- Custom (details below)
Index Mapping
Mapping not relevant
Bug Description
Before #4892, the types are injected at runtime:
However, the standard SQL requires the return type to be inferrable before executing the query. Currently, the argument is of type ANY, making the result also typed ANY. Therefore, the result array is an ANY array. For this case, it is indeed inferrable -- the array is an INTEGER ARRAY, meaning that x should be of type INTEGER instead of ANY.
Impact:
doctest in collections.md
Environment Information
OpenSearch Version: 3.4 (with PR #4892 )
Screenshots
File "/Users/yuanchu/src/sql/doctest/../docs/user/ppl/functions/collection.md", line 167, in /Users/yuanchu/src/sql/doctest/../docs/user/ppl/functions/collection.md
Failed example:
ppl_cmd.process('source=people | eval array = array(1, -2, 3), result = transform(array, x -> x + 2) | fields result | head 1')
Expected:
fetched rows / total rows = 1/1
+---------+
| result |
|---------|
| [3,0,5] |
+---------+
Got:
fetched rows / total rows = 1/1
+---------------+
| result |
|---------------|
| [3.0,0.0,5.0] |
+---------------+
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Assessment
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