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https://issues.apache.org/jira/browse/CALCITE-5995?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17765837#comment-17765837
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Julian Hyde commented on CALCITE-5995:
--------------------------------------
You are using a global (static) cache. Can you make the cache belong to a
function instance? That was the pattern I followed in CALCITE-5914, because I
am worried about cache persisting beyond a query's lifetime.
> add cache to dejsonize function in JsonFunctions
> ------------------------------------------------
>
> Key: CALCITE-5995
> URL: https://issues.apache.org/jira/browse/CALCITE-5995
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.35.0
> Reporter: xiaogang zhou
> Priority: Minor
> Fix For: 1.36.0
>
>
> I used the json_value function to parse json values. And I found calcite's
> json_value function does not cache the dejsonized objects, which could cause
> some performance issue in situation below as the dejsonize function being
> called repeatedly unnecessarily.
>
> {code:java}
> select
> json_value(A, 'xxx'),
> json_value(A, 'yyy'),
> json_value(A, 'zzz'),...
> from some_table;
> {code}
>
>
> As project like flink uses the json_value to codegen it's own json_value
> function, I think this could cause a bad performance for users. So I suggest
> to introduce a cache in
>
> org.apache.calcite.runtime.JsonFunctions#dejsonize
>
> and the solution is very common in projects like hive
> [https://github.com/apache/hive/blob/storage-branch-2.3/ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDTFJSONTuple.java]
>
> and of course, this feature can be turned on only some certain config is
> setted. And if this is acceptable, I think I can take the ticket. thx
>
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