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https://issues.apache.org/jira/browse/CALCITE-3513?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17020458#comment-17020458
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Julian Hyde commented on CALCITE-3513:
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Ok, so I think the subject of this case should be "When a table function
returns null, treat it as an empty relation". When we have that change, we can
treat table functions the same as regular functions.
> Unify TableFunction implementor's NullPolicy and its behavior
> -------------------------------------------------------------
>
> Key: CALCITE-3513
> URL: https://issues.apache.org/jira/browse/CALCITE-3513
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.21.0
> Reporter: Feng Zhu
> Assignee: Feng Zhu
> Priority: Major
> Labels: pull-request-available
> Time Spent: 4h
> Remaining Estimate: 0h
>
> *Example:*
> TableFunctionTest#_testMultipleScannableTableFunctionWithNamedParameters_
> {code:java}
> SQL3:
> select * from table("s"."Maze"(HEIGHT => 3, WIDTH => 5){code}
> *RelNode:*
> {code:java}
> EnumerableTableFunctionScan(invocation=[Maze(5, 3, DEFAULT())],
> rowType=[RecordType(VARCHAR(12) S)], elementType=[class
> [Ljava.lang.Object;]){code}
> *Code:*
> {code:java}
> public org.apache.calcite.linq4j.Enumerable bind(final
> org.apache.calcite.DataContext root) {
> return
> org.apache.calcite.runtime.Enumerables.slice0(org.apache.calcite.util.Smalls.MazeTable.generate2(5,
> 3, null).scan(root));
> }{code}
> *Inconsistency:*
> Current now, _*TableFunctionImpl*_ creats its implementor with
> _*NullPolicy.ANY*_. If we follow the NullPolicy, it will generate null,
> rather than MazeTable.generate2(5, 3, null)
> It is not consistent with its definition.
> {code:java}
> /** If any of the arguments are null, return null. */
> ANY{code}
> *Root Cause:*
> The issue is covered due to current codegen's mechanism, which combines a
> mutable states (_*NullAs*_) and *_NullPolicy_* together to determine the
> semantics for null checking.
> The implementation for example query actually do nothing about arguments'
> null checking.
> We can ignore this minor case at the moment, but the inconsistency prevents
> further optimizations. However, under current codegen implementation, I
> failed to figure out a test case to trigger the problem.
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