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https://issues.apache.org/jira/browse/FLINK-9477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17267609#comment-17267609
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Jark Wu commented on FLINK-9477:
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I think JSON function is an important long-missing feature and we should
support this in the next release.
But I reconsider the API again, and have some thoughts.
Currentlly, all the json path string requires the {{lax}} or {{strict}} prefix,
e.g. {{JSON_VALUE(json, 'lax $.foo')}}.
Strict mode is used to examine data from a strict schema perspective, for
example, to look for data that diverges from an expected schema. Therefore,
strict mode raises an error if the data does not strictly adhere to the
requirements of a path expression. Lax mode is intended to be more forgiving,
so lax mode converts errors to empty JSON sequences.
However, Flink as a bigdata streaming processing system, an long-running
service, the job shouldn't fail even dirty data arrives. Even if we want to
examine dirty data, this should be a job level configuration and take effect to
all functions. Therefore, we don't support "strict" mode and users have to
write "lax" prefix, this sounds not useful. Why not eliminate the "lax" prefix?
I also investivate other databases/systems, all of them don't follow the SQL
standard, and only use the json path string without "lax" or "strict" prefix,
e.g. MySQL[1], Oracle[2], SqlServer[3], Trino(Presto)[4].
Thus, I suggest to support the json path without "lax" or "strict" prefix and
converts errors to empty or null json sequences.
What do you think ? [~x1q1j1] [~lzljs3620320] [~docete] [~danny0405] (the FLIP
voters).
[1]:
https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#function_json-extract
[2]: https://docs.oracle.com/database/121/ADXDB/json.htm#ADXDB6263
[3]:
https://docs.microsoft.com/en-us/sql/t-sql/functions/json-value-transact-sql?view=sql-server-2017
[4]: https://trino.io/docs/current/functions/json.html#json-functions
> FLIP-90: Support SQL 2016 JSON functions in Flink SQL
> -----------------------------------------------------
>
> Key: FLINK-9477
> URL: https://issues.apache.org/jira/browse/FLINK-9477
> Project: Flink
> Issue Type: New Feature
> Components: Table SQL / API
> Reporter: Shuyi Chen
> Assignee: Forward Xu
> Priority: Major
> Fix For: 1.13.0
>
>
> FLIP Link
> https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=141724550
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