[
https://issues.apache.org/jira/browse/FLINK-4469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15674228#comment-15674228
]
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_r88482480
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/functions/utils/TableSqlFunction.scala
---
@@ -0,0 +1,99 @@
+/*
+ * 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.functions.utils
+
+import com.google.common.base.Predicate
+import org.apache.calcite.rel.`type`.RelDataType
+import org.apache.calcite.sql._
+import org.apache.calcite.sql.`type`._
+import org.apache.calcite.sql.parser.SqlParserPos
+import org.apache.calcite.sql.validate.SqlUserDefinedTableFunction
+import org.apache.calcite.util.Util
+import org.apache.flink.api.common.typeinfo.TypeInformation
+import org.apache.flink.api.table.functions.TableFunction
+import org.apache.flink.api.table.FlinkTypeFactory
+
+import scala.collection.JavaConversions._
+import java.util
+
+import org.apache.flink.api.table.plan.schema.FlinkTableFunctionImpl
+
+/**
+ * Calcite wrapper for user-defined table functions.
+ */
+class TableSqlFunction(
+ name: String,
+ udtf: TableFunction[_],
+ rowTypeInfo: TypeInformation[_],
+ returnTypeInference: SqlReturnTypeInference,
+ operandTypeInference: SqlOperandTypeInference,
+ operandTypeChecker: SqlOperandTypeChecker,
+ paramTypes: util.List[RelDataType],
+ functionImpl: FlinkTableFunctionImpl[_])
+ extends SqlUserDefinedTableFunction(
+ new SqlIdentifier(name, SqlParserPos.ZERO),
+ returnTypeInference,
+ operandTypeInference,
+ operandTypeChecker,
+ paramTypes,
+ functionImpl) {
+
+ def getTableFunction = udtf
+
+ def getRowTypeInfo = rowTypeInfo
+
+ def getPojoFieldMapping = functionImpl.fieldIndexes
+
+}
+
+object TableSqlFunction {
+ /**
+ *
+ * @param name function name (used by SQL parser)
+ * @param udtf user defined table function to be called
+ * @param rowTypeInfo the row type information generated by the table
function
+ * @param typeFactory type factory for converting Flink's between
Calcite's types
+ * @param functionImpl calcite table function schema
+ * @return
+ */
+ def apply(
+ name: String,
+ udtf: TableFunction[_],
+ rowTypeInfo: TypeInformation[_],
+ typeFactory: FlinkTypeFactory,
+ functionImpl: FlinkTableFunctionImpl[_]): TableSqlFunction = {
+
+ val argTypes: util.List[RelDataType] = new util.ArrayList[RelDataType]
+ val typeFamilies: util.List[SqlTypeFamily] = new
util.ArrayList[SqlTypeFamily]
+ for (o <- functionImpl.getParameters) {
+ val relType: RelDataType = o.getType(typeFactory)
+ argTypes.add(relType)
+ typeFamilies.add(Util.first(relType.getSqlTypeName.getFamily,
SqlTypeFamily.ANY))
--- End diff --
Could you add some comments in this method?
> 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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