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ASF GitHub Bot commented on FLINK-4469: --------------------------------------- Github user twalthr commented on a diff in the pull request: https://github.com/apache/flink/pull/2653#discussion_r90033099 --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/TableFunctionCall.scala --- @@ -0,0 +1,110 @@ +/* + * 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.api.table + +import org.apache.flink.api.common.typeinfo.TypeInformation +import org.apache.flink.api.table.expressions.{Expression, UnresolvedFieldReference} +import org.apache.flink.api.table.functions.TableFunction +import org.apache.flink.api.table.functions.utils.UserDefinedFunctionUtils.getFieldInfo +import org.apache.flink.api.table.plan.logical.{LogicalNode, LogicalTableFunctionCall} + + +/** + * A [[TableFunctionCall]] represents a call to a [[TableFunction]] with actual parameters. + * + * For Scala users, Flink will help to parse a [[TableFunction]] to [[TableFunctionCall]] + * implicitly. For Java users, Flink will help to parse a string expression to + * [[TableFunctionCall]]. So users do not need to create a [[TableFunctionCall]] manually. + * + * @param functionName function name + * @param tableFunction user-defined table function + * @param parameters actual parameters of function + * @param resultType type information of returned table + */ +case class TableFunctionCall( + functionName: String, + tableFunction: TableFunction[_], + parameters: Seq[Expression], + resultType: TypeInformation[_]) { + + private var aliases: Option[Seq[Expression]] = None + + /** + * Assigns an alias for this table function returned fields that the following `select()` clause + * can refer to. + * + * @param aliasList alias for this table function returned fields + * @return this table function call + */ + def as(aliasList: Expression*): TableFunctionCall = { + this.aliases = Some(aliasList) + this + } + + /** + * Converts an API class to a logical node for planning. + */ + private[flink] def toLogicalTableFunctionCall(child: LogicalNode): LogicalTableFunctionCall = { + val originNames = getFieldInfo(resultType)._1 + + // determine the final field names + val fieldNames = if (aliases.isDefined) { + val aliasList = aliases.get + if (aliasList.length != originNames.length) { + throw ValidationException( + s"List of column aliases must have same degree as table; " + + s"the returned table of function '$functionName' has ${originNames.length} " + + s"columns (${originNames.mkString(",")}), " + + s"whereas alias list has ${aliasList.length} columns") + } else if (!aliasList.forall(_.isInstanceOf[UnresolvedFieldReference])) { + throw ValidationException("Alias only accept name expressions as arguments") + } else { + aliasList.map(_.asInstanceOf[UnresolvedFieldReference].name).toArray + } + } else { + originNames + } + + LogicalTableFunctionCall( + functionName, + tableFunction, + parameters, + resultType, + fieldNames, + child) + } +} + + +case class TableFunctionCallBuilder[T: TypeInformation](udtf: TableFunction[T]) { --- End diff -- I would move this class to `org.apache.flink.api.scala.table`. It is Scala API only and fits better next to `expressionDsl.scala` > Add support for user defined table function in Table API & SQL > -------------------------------------------------------------- > > Key: FLINK-4469 > URL: https://issues.apache.org/jira/browse/FLINK-4469 > Project: Flink > Issue Type: New Feature > Components: Table API & SQL > Reporter: Jark Wu > Assignee: Jark Wu > > Normal user-defined functions, such as concat(), take in a single input row > and output a single output row. In contrast, table-generating functions > transform a single input row to multiple output rows. It is very useful in > some cases, such as look up in HBase by rowkey and return one or more rows. > Adding a user defined table function should: > 1. inherit from UDTF class with specific generic type T > 2. define one or more evel function. > NOTE: > 1. the eval method must be public and non-static. > 2. the generic type T is the row type returned by table function. Because of > Java type erasure, we can’t extract T from the Iterable. > 3. use {{collect(T)}} to emit table row > 4. eval method can be overload. Blink will choose the best match eval method > to call according to parameter types and number. > {code} > public class Word { > public String word; > public Integer length; > } > public class SplitStringUDTF extends UDTF<Word> { > public Iterable<Word> eval(String str) { > if (str != null) { > for (String s : str.split(",")) { > collect(new Word(s, s.length())); > } > } > } > } > // in SQL > tableEnv.registerFunction("split", new SplitStringUDTF()) > tableEnv.sql("SELECT a, b, t.* FROM MyTable, LATERAL TABLE(split(c)) AS > t(w,l)") > // in Java Table API > tableEnv.registerFunction("split", new SplitStringUDTF()) > // rename split table columns to “w” and “l” > table.crossApply("split(c) as (w, l)") > .select("a, b, w, l") > // without renaming, we will use the origin field names in the POJO/case/... > table.crossApply("split(c)") > .select("a, b, word, length") > // in Scala Table API > val split = new SplitStringUDTF() > table.crossApply(split('c) as ('w, 'l)) > .select('a, 'b, 'w, 'l) > // outerApply for outer join to a UDTF > table.outerApply(split('c)) > .select('a, 'b, 'word, 'length) > {code} > See [1] for more information about UDTF design. > [1] > https://docs.google.com/document/d/15iVc1781dxYWm3loVQlESYvMAxEzbbuVFPZWBYuY1Ek/edit# -- This message was sent by Atlassian JIRA (v6.3.4#6332)