[
https://issues.apache.org/jira/browse/FLINK-4469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15711944#comment-15711944
]
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_r90052039
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/codegen/calls/TableFunctionCallGen.scala
---
@@ -0,0 +1,78 @@
+/*
+ * 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.codegen.calls
+
+import org.apache.flink.api.common.typeinfo.TypeInformation
+import org.apache.flink.api.table.codegen.CodeGenUtils._
+import org.apache.flink.api.table.codegen.{CodeGenException,
CodeGenerator, GeneratedExpression}
+import org.apache.flink.api.table.functions.TableFunction
+import
org.apache.flink.api.table.functions.utils.UserDefinedFunctionUtils._
+
+/**
+ * Generates a call to user-defined [[TableFunction]].
+ *
+ * @param tableFunction user-defined [[TableFunction]] that might be
overloaded
+ * @param signature actual signature with which the function is called
+ * @param returnType actual return type required by the surrounding
+ */
+class TableFunctionCallGen(
+ tableFunction: TableFunction[_],
+ signature: Seq[TypeInformation[_]],
+ returnType: TypeInformation[_])
+ extends CallGenerator {
+
+ override def generate(
+ codeGenerator: CodeGenerator,
+ operands: Seq[GeneratedExpression])
+ : GeneratedExpression = {
+ // determine function signature
+ val matchingSignature = getSignature(tableFunction.getClass, signature)
+ .getOrElse(throw new CodeGenException("No matching signature
found."))
+
+ // convert parameters for function (output boxing)
+ val parameters = matchingSignature
+ .zip(operands)
+ .map { case (paramClass, operandExpr) =>
+ if (paramClass.isPrimitive) {
+ operandExpr
+ } else {
+ val boxedTypeTerm =
boxedTypeTermForTypeInfo(operandExpr.resultType)
+ val boxedExpr =
codeGenerator.generateOutputFieldBoxing(operandExpr)
+ val exprOrNull: String = if (codeGenerator.nullCheck) {
+ s"${boxedExpr.nullTerm} ? null : ($boxedTypeTerm)
${boxedExpr.resultTerm}"
+ } else {
+ boxedExpr.resultTerm
+ }
+ boxedExpr.copy(resultTerm = exprOrNull)
+ }
+ }
+
+ // generate function call
+ val functionReference =
codeGenerator.addReusableInstance(tableFunction)
+ val functionCallCode =
+ s"""
+ |${parameters.map(_.code).mkString("\n")}
+ |$functionReference.clear();
+
|$functionReference.eval(${parameters.map(_.resultTerm).mkString(", ")});
+ |""".stripMargin
+
+ // has no result
+ GeneratedExpression(functionReference, "false", functionCallCode,
returnType)
--- End diff --
Btw. I created the constant `GeneratedExpression.NEVER_NULL` instead of
`"false"` to make it more readable.
> 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#
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