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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-6196) Support dynamic schema in Table Function
Date Wed, 05 Apr 2017 16:50:42 GMT

    [ https://issues.apache.org/jira/browse/FLINK-6196?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15957213#comment-15957213
] 

ASF GitHub Bot commented on FLINK-6196:
---------------------------------------

Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3623#discussion_r109931036
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/schema/FlinkTableFunction.scala
---
    @@ -0,0 +1,55 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +package org.apache.flink.table.plan.schema
    +
    +import java.lang.reflect.{Method, Type}
    +import java.util
    +
    +import org.apache.calcite.rel.`type`.{RelDataType, RelDataTypeFactory}
    +import org.apache.calcite.schema.TableFunction
    +import org.apache.calcite.schema.impl.ReflectiveFunctionBase
    +import org.apache.flink.api.common.typeinfo.TypeInformation
    +import org.apache.flink.table.functions.{TableFunction => FlinkUDTF}
    +
    +/**
    +  * This is heavily inspired by Calcite's [[org.apache.calcite.schema.impl.TableFunctionImpl]].
    +  * We need it in order to create a [[org.apache.flink.table.functions.utils.TableSqlFunction]].
    +  * The main difference is that we override the [[getResultType()]] and [[getElementType()]].
    +  *
    +  * @param tableFunction The Table Function instance
    +  * @param evalMethod The eval() method of the [[tableFunction]]
    +  */
    +abstract class FlinkTableFunction(
    +    tableFunction: FlinkUDTF[_],
    +    evalMethod: Method)
    +  extends ReflectiveFunctionBase(evalMethod)
    +  with TableFunction {
    +
    +  override def getElementType(arguments: util.List[AnyRef]): Type = classOf[Array[Object]]
    +
    +  /**
    +    * Returns the TypeInformation for internal usage, i.e. code generation.
    +    */
    +  def getResultType(arguments: util.List[AnyRef]): TypeInformation[_]
    +
    +  /**
    +    * Returns the record type of the table function to integrate with Calcite.
    +    */
    +  def getRowType(typeFactory: RelDataTypeFactory, arguments: util.List[AnyRef]): RelDataType
    --- End diff --
    
    This is method is not overridden and I think it can be removed.


> Support dynamic schema in Table Function
> ----------------------------------------
>
>                 Key: FLINK-6196
>                 URL: https://issues.apache.org/jira/browse/FLINK-6196
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table API & SQL
>            Reporter: Zhuoluo Yang
>            Assignee: Zhuoluo Yang
>
> In many of our use cases. We have to decide the schema of a UDTF at the run time. For
example. udtf('c1, c2, c3') will generate three columns for a lateral view. 
> Most systems such as calcite and hive support this feature. However, the current implementation
of flink didn't implement the feature correctly.



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