[jira] [Updated] (CALCITE-3760) Rewriting non-deterministic function can break query semantics

["Jin Xing (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-3760?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jin Xing updated CALCITE-3760:
------------------------------
    Summary: Rewriting non-deterministic function can break query semantics  (was: Rewriting function without considering determinism can break query semantics)

> Rewriting non-deterministic function can break query semantics
> --------------------------------------------------------------
>
>                 Key: CALCITE-3760
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3760
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>            Reporter: Jin Xing
>            Assignee: Jin Xing
>            Priority: Major
>
> Calcite rewrite some *SqlFunctions* during validation. But whether the function is deterministic is not considered. For a non-deterministic operator, the rewriting can break semantics. Additionally there's no interface for user to specify the determinism for a UDF/UDAF. 
> Say I have non-deterministic UDF & UDAF and run sql like below
> {code:java}
> select coalesce(udf(col0), 100) from foo;
> select nullif(udaf(col0), 1024) from foo;{code}
> They will be rewritten as
> {code:java}
> select case when udf(col0) is not null then udf(col0) else 100 end
> from foo;
> select case when udaf(col0)=1024 then null udaf(col0)
> from foo{code}
> As we can see that non-deterministic UDF & UDAF are called multiple times after written. Thus the condition in WHEN clause might NOT be held all the time.
> We need to provide an interface for user to specify the determinism in UDF/UDAF and consider whether a SqlNode is deterministic when rewriting.



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