amaliujia edited a comment on issue #1587: [CALCITE-3272] Support TUMBLE as Table Valued Function including an enumerable implementation, stream.iq and DESCRIPTOR URL: https://github.com/apache/calcite/pull/1587#issuecomment-568799995 @danny0405 I understand your concerns. Current implementation is less extensible as there will be more built-in table-valued function implementations and we cannot have many if-else with their own enumerable implementations. An implementor interface would be desired for each implementation. However, I believe current `CallImplementor` or `NotNullImplementor` is not enough for table-valued functions like `tumbling`. Table-valued functions cannot be done by the following code. ``` // RexCalls that are suitable for `CallImplementor` or `NotNullImplementor` for (operand : call.operands()) { translate(operand); } translate(call, translatedOperands); ``` Because at least it requires `inputPhysType`, and very likely require `outputPhysType`and others params. Likely, table-valued function need following this: ``` translate(table_valued_fucntion_call.operands()) // with the help of `inputPhysType`. translate(table_valued_fucntion_call); ``` I can give a simple example: assume there is a table-valued function(TVF) that takes an table as input and a descriptor of a single column name. This TVF always return a table with all distinct values from one of columns that is specified by the descriptor in input table. In this example, `inputPhysType` will be needed. I think we need a new interface for this purpose, I have filed [CALCITE-3629](https://issues.apache.org/jira/browse/CALCITE-3629). In this PR, I made some changes to move some Tumbling code to `EnumUtils`, per the existing practice of enumerables and not every line of code can be moved out. Meanwhile, I would suggest to solve [CALCITE-3629](https://issues.apache.org/jira/browse/CALCITE-3629) when I add `HOP` implementation (a work after this PR). The rationale is we need more implementations to build an abstraction and then which leads to a good interface design.
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