[jira] [Closed] (FLINK-25502) eval method of Flink ScalerFunction only run one time

["Timo Walther (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-25502?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Timo Walther closed FLINK-25502.
--------------------------------
    Resolution: Invalid

Please take a look at: https://nightlies.apache.org/flink/flink-docs-master/docs/dev/table/functions/udfs/#determinism

{code}
If a function is called with constant expressions or constant expressions can be derived from the given statement, a function is pre-evaluated for constant expression reduction and might not be executed on the cluster anymore. Unless isDeterministic() is used to disable constant expression reduction in this case. For example, the following calls to ABS are executed during planning: SELECT ABS(-1) FROM t and SELECT ABS(field) FROM t WHERE field = -1; whereas SELECT ABS(field) FROM t is not.
{code}

> eval method of Flink ScalerFunction only run one time
> -----------------------------------------------------
>
>                 Key: FLINK-25502
>                 URL: https://issues.apache.org/jira/browse/FLINK-25502
>             Project: Flink
>          Issue Type: Bug
>          Components: Table SQL / API
>    Affects Versions: 1.14.2
>            Reporter: Spongebob
>            Priority: Major
>
> assume that there is one scalerFunction named `id` which's eval method takes no arguments and return increasing int value on each calling. Now I found that when I call `id()` function in  FlinkSQL that has 3 rows , the eval method only was called one time so I got the same id value for each row. The sql likes 'SELECT f0, id() FROM T'.
> So I decided to define one argument on `eval` method.  When I execute sql 'SELECT f0, id(1) FROM T' I got the same id value still. But when I execute sql 'SELECT f0, id(f0) FROM T' then I could get the correct id value, because the eval method was called by three times now.



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