luchunliang opened a new issue, #12189:
URL: https://github.com/apache/inlong/issues/12189
### Description
`ArrayParser` in Transform SDK is bound to
`net.sf.jsqlparser.expression.ArrayExpression`, i.e. the SQL bracket syntax
`expr[index_or_key]`. Historically it only supported two shapes:
1. `List<?>[Number]` — access a Java list element by numeric index;
2. `JsonArray[Number]` — access a `com.google.gson.JsonArray` element by
numeric index.
However, several very common expressions in real pipelines rely on
**key-based bracket access** rather than numeric indexing, for example:
- `STR_TO_MAP(URL_DECODE(event_value), '&', '=')['HY50']` — pick a value out
of a `str_to_map` result inside `SELECT` / `WHERE`;
- `JSON_TO_STRUCT($root.person)['name']` or a raw `JsonObject` from other
functions — pick a field out of a JSON object by key.
Before this change these expressions returned `null`, forcing users to
introduce intermediate columns or extra function calls (e.g. `PARSE_URL` with
`QUERY`) and making the SQL harder to read and maintain.
This issue proposes extending `ArrayParser` so that `expr[key]` works
uniformly for:
- `List<?>` indexed by a `Number` (existing behavior — unchanged);
- **`Map<?, ?>` indexed by any key type — NEW;**
- `JsonArray` indexed by a `Number` (existing behavior — unchanged);
- **`JsonObject` indexed by a `String` key — NEW.**
For the JSON branches, primitive results are unwrapped to their natural Java
types (`String`, `Boolean`, `Number`); nested `JsonArray` / `JsonObject`
results are preserved so downstream operators can keep drilling in.
### Use case
1. **KV map lookup after `STR_TO_MAP`** — decode a URL-encoded query string
and pluck a specific parameter in one line:
```sql
SELECT
STR_TO_MAP(URL_DECODE(event_value), '&', '=')['HY50'] AS HY50
FROM source
WHERE STR_TO_MAP(URL_DECODE(event_value), '&', '=')['HY50'] =
'welfare_milestone_operations'
AND event_code = 'OnPageEnter';
```
2. **JSON key access** — read fields off a raw `JsonObject` produced by JSON
helper functions using the intuitive `obj['field']` syntax, without additional
casting.
3. **Consistency** — align bracket-access semantics with common SQL /
JSONPath expectations, reduce boilerplate, and remove edge cases where a
valid-looking expression silently returned `null`.
### Are you willing to submit PR?
- [x] Yes, I am willing to submit a PR!
### Code of Conduct
- [x] I agree to follow this project's [Code of
Conduct](https://www.apache.org/foundation/policies/conduct)
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