[jira] [Created] (FLINK-40233) JSON functions return NULL when sharing a parsed input

["Gustavo de Morais (Jira)" <ji...@apache.org>]

Gustavo de Morais created FLINK-40233:
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             Summary: JSON functions return NULL when sharing a parsed input
                 Key: FLINK-40233
                 URL: https://issues.apache.org/jira/browse/FLINK-40233
             Project: Flink
          Issue Type: Bug
          Components: Table SQL / API
    Affects Versions: 2.3.0
            Reporter: Gustavo de Morais
            Assignee: Gustavo de Morais


When two JSON functions share the same input in one query, the second call can wrongly return NULL.

The parse result is cached and reused to avoid re-parsing the same input. But if an earlier JSON call short-circuits and returns NULL before parsing (for example a NULL path argument), the cache is marked as populated while the parse never actually ran. The second function then reuses an empty parse result and returns NULL.


{code:java}
SELECT json_value(v, cast(null as string)), json_length(v)
FROM (values('{"a":1, "b":2}')) AS t(v);
-- returns (NULL, NULL), expected (NULL, 2)

SELECT json_value(v, cast(null as string)), json_value(v, '$.a')
FROM (values('{"a":1, "b":2}')) AS t(v);
-- returns (NULL, NULL), expected (NULL, 1)

SELECT json_value(v, cast(null as string)), json_query(v, '$.a')
FROM (values('{"a":{"b":1}, "b":2}')) AS t(v);
-- returns (NULL, NULL), expected (NULL, {"b":1}) {code}
The reusable-parse tracking in {{CodeGeneratorContext}} records the input as already parsed even though the first call exited before parsing it.



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