zhang-jianq opened a new issue, #13467:
URL: https://github.com/apache/gluten/issues/13467
### Description
## Motivation
Flink's `JSON_VALUE` is a core SQL/JSON path expression — it extracts a
scalar from a JSON document and returns it as a typed value. Today gluten-flink
does not map it, so any Calc projecting `JSON_VALUE(...)` fails function
offload ("Function not supported") and stays on the native path.
## Proposal
Offload it to the velox flinksql function set:
- velox side (companion PR): a Flink-semantics `JSON_VALUE` under
`velox/functions/flinksql/` —
`json_value(json, path, onEmpty, onEmptyDefault, onError, onErrorDefault)
-> varchar`. It extracts the scalar referenced by the SQL/JSON path via
simdjson, routes every non-scalar case to **ON EMPTY** in `lax` mode (or **ON
ERROR** in `strict`/default mode), and applies the **NULL / ERROR / DEFAULT**
handler. velox's prestosql `json_extract_scalar(json, path)` is not reused
because it collapses both ON EMPTY and ON ERROR to NULL and has no RETURNING
conversion.
- planner side (this repo): `JSON_VALUE -> JsonValueRexCallConverter` — a
dedicated converter that parses the Flink operand layout (json expression, path
literal, then alternating `(behavior, [default], ON EMPTY|ON ERROR)` triplets)
into the 7-arg velox call, and wraps a non-VARCHAR `RETURNING` in a `CAST`.
Semantics to preserve: `lax`/`strict` routing, the three handlers, scalar
extraction of string/number/boolean, null propagation (NULL json in -> NULL
out), and `RETURNING` type conversion.
Gluten version: main branch (gluten-flink)
### Gluten version
main branch
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