Ramin Gharib created FLINK-41086:
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Summary: JSON_LENGTH and JSON_TYPE fail the job when a JSON path
function throws
Key: FLINK-41086
URL: https://issues.apache.org/jira/browse/FLINK-41086
Project: Flink
Issue Type: Bug
Components: Table SQL / Runtime
Affects Versions: 2.4.0
Reporter: Ramin Gharib
h3. Problem
{{JSON_LENGTH(json, path)}} and {{JSON_TYPE(json, path)}} should return NULL
when the path does not locate a value. {{SqlJsonUtils#jsonLength}} and
{{SqlJsonUtils#jsonType}} only catch {{InvalidPathException}} around
{{JsonPath#read}}. Path functions such as {{min()}} or {{avg()}} throw the
parent {{JsonPathException}} on their own, for example over an empty array.
{{JsonPathInputTypeStrategy}} only rejects the {{lax}}/{{strict}} prefix, so
these paths pass validation. The exception escapes and fails the job. With
{{f0}} as a STRING column:
||{{f0}}||Query||Expected||Actual||
|{{[]}}|{{JSON_LENGTH(f0, '$.min()')}}|NULL|{{JsonPathException: Aggregation
function attempted to calculate value using empty array}}|
|{{\{"a": []\}}}|{{JSON_TYPE(f0, '$.a.avg()')}}|NULL|the same exception|
|{{\{"a": [1, 2]\}}}|{{JSON_LENGTH(f0, '$.a[*].min()')}}|NULL|the same
exception|
{{JSON_VALUE}}, {{JSON_QUERY}} and {{JSON_EXISTS}} go through
{{SqlJsonUtils#jsonApiCommonSyntax}}, which catches any {{Exception}} around
the same call.
h3. Proposal
Catch {{JsonPathException}} in both methods. It is the parent of
{{InvalidPathException}} and {{PathNotFoundException}}, so the existing cases
keep returning NULL.
h3. Tests
* The queries above in {{JsonFunctionsITCase}}, for SQL and the Table API.
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