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https://issues.apache.org/jira/browse/FLINK-40901?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated FLINK-40901:
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Labels: pull-request-available (was: )
> JSON functions return the result of a previous row when JSON_TYPE or
> JSON_LENGTH is skipped
> -------------------------------------------------------------------------------------------
>
> Key: FLINK-40901
> URL: https://issues.apache.org/jira/browse/FLINK-40901
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Planner
> Reporter: Moritz Manner
> Assignee: Vas Shabu
> Priority: Major
> Labels: pull-request-available
>
> JSON_TYPE and JSON_LENGTH share the parsed input if they are called on the
> same column, but only the first call in the generated code parses it. If that
> call isn't evaluated for a row, the following calls use the input that was
> parsed for an earlier row. This happens, for example, when the first call is
> in a CASE branch that isn't taken, or behind an OR that short-circuits. If
> there is no earlier row, they return NULL.
> JSON_VALUE and JSON_QUERY on the same column are affected as well if a
> JSON_TYPE or JSON_LENGTH call comes before them.
> The result is wrong, and there is no error.
> h3. Reproduce
> JSON_LENGTH returns the length of the previous row:
> {code:sql}
> SELECT id, CASE WHEN id > 1 THEN JSON_TYPE(j) END, JSON_LENGTH(j)
> FROM (VALUES (2, '[1,2,3]'), (1, '[1]')) AS t(id, j);
> {code}
> ||id||EXPR$1||EXPR$2||
> |2|array|3|
> |1|NULL|3|
> The JSON_LENGTH of the second row should be 1.
> JSON_TYPE returns the type of the previous row:
> {code:sql}
> SELECT id, CASE WHEN id > 1 THEN JSON_LENGTH(j) END, JSON_TYPE(j)
> FROM (VALUES (2, '[1,2,3]'), (1, '{"a":1}')) AS t(id, j);
> {code}
> ||id||EXPR$1||EXPR$2||
> |2|3|array|
> |1|NULL|array|
> The JSON_TYPE of the second row should be object.
> JSON_VALUE returns the value of the previous row:
> {code:sql}
> SELECT id, CASE WHEN id > 1 THEN JSON_TYPE(j) END, JSON_VALUE(j, '$.a')
> FROM (VALUES (2, '{"a":"x"}'), (1, '{"a":"y"}')) AS t(id, j);
> {code}
> ||id||EXPR$1||EXPR$2||
> |2|object|x|
> |1|NULL|x|
> The JSON_VALUE of the second row should be y.
> JSON_QUERY returns the value of the previous row:
> {code:sql}
> SELECT id, CASE WHEN id > 1 THEN JSON_TYPE(j) END, JSON_QUERY(j, '$.a')
> FROM (VALUES (2, '{"a":[1]}'), (1, '{"a":[2]}')) AS t(id, j);
> {code}
> ||id||EXPR$1||EXPR$2||
> |2|object|[1]|
> |1|NULL|[1]|
> The JSON_QUERY of the second row should be [2].
> The same happens in a WHERE clause:
> {code:sql}
> SELECT id, JSON_LENGTH(j)
> FROM (VALUES (2, '[1,2,3]'), (1, '[1]')) AS t(id, j)
> WHERE id > 1 OR JSON_TYPE(j) = 'array';
> {code}
> This returns (2, NULL) and (1, 1). It should return (2, 3) and (1, 1).
> h3. Notes
> * Only the first JSON function call on a column decides this. If it is
> JSON_VALUE or JSON_QUERY, the results are correct, even if that call is
> skipped.
> * If the call outside the CASE comes before the CASE, the result is correct.
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