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https://issues.apache.org/jira/browse/FLINK-7062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16651748#comment-16651748
 ] 

ASF GitHub Bot commented on FLINK-7062:
---------------------------------------

dawidwys commented on a change in pull request #6815:  [FLINK-7062][cep][table] 
Added basic support for MATCH_RECOGNIZE
URL: https://github.com/apache/flink/pull/6815#discussion_r225551310
 
 

 ##########
 File path: 
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/MatchCodeGenerator.scala
 ##########
 @@ -0,0 +1,320 @@
+/*
+ * 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.codegen
+
+import java.util
+
+import org.apache.calcite.rex._
+import org.apache.calcite.sql.fun.SqlStdOperatorTable._
+import org.apache.flink.api.common.functions._
+import org.apache.flink.api.common.typeinfo.TypeInformation
+import org.apache.flink.api.java.typeutils.ListTypeInfo
+import org.apache.flink.cep.pattern.conditions.IterativeCondition
+import org.apache.flink.cep.{PatternFlatSelectFunction, PatternSelectFunction}
+import org.apache.flink.table.api.{TableConfig, TableException}
+import org.apache.flink.table.codegen.CodeGenUtils.{boxedTypeTermForTypeInfo, 
newName, primitiveDefaultValue}
+import org.apache.flink.table.codegen.Indenter.toISC
+import org.apache.flink.table.plan.schema.RowSchema
+import org.apache.flink.util.Collector
+import org.apache.flink.util.MathUtils.checkedDownCast
+import java.lang.{Long => JLong}
+
+import scala.collection.JavaConverters._
+
+/**
+  * A code generator for generating CEP related functions.
+  *
+  * @param config configuration that determines runtime behavior
+  * @param nullableInput input(s) can be null.
+  * @param input type information about the first input of the Function
+  * @param currentPattern if generating condition the name of pattern, which 
the condition will
+  *                       be applied to
+  */
+class MatchCodeGenerator(
+    config: TableConfig,
+    nullableInput: Boolean,
+    input: TypeInformation[_ <: Any],
+    currentPattern: Option[String] = None)
+  extends CodeGenerator(config, nullableInput, input){
+
+  def generateMatchFunction[F <: Function, T <: Any](
+    name: String,
+    clazz: Class[F],
+    bodyCode: String,
+    returnType: TypeInformation[T])
+  : GeneratedFunction[F, T] = {
+    // This is a separate method from FunctionCodeGenerator#generateFunction 
because as of now
+    // functions in CEP library do not support rich interfaces
+    val funcName = newName(name)
+    val collectorTypeTerm = classOf[Collector[Any]].getCanonicalName
+    val (functionClass, signature, inputStatements, isInterface) =
+      if (clazz == classOf[IterativeCondition[_]]) {
+        val baseClass = classOf[IterativeCondition[_]]
+        val inputTypeTerm = boxedTypeTermForTypeInfo(input)
+        val contextType = 
classOf[IterativeCondition.Context[_]].getCanonicalName
+
+        (baseClass,
+          s"boolean filter( Object _in1, $contextType $contextTerm)",
+          List(s"$inputTypeTerm $input1Term = ($inputTypeTerm) _in1;"),
+          false)
+      } else if (clazz == classOf[PatternSelectFunction[_, _]]) {
+        val baseClass = classOf[PatternSelectFunction[_, _]]
+        val inputTypeTerm =
+          s"java.util.Map<String, 
java.util.List<${boxedTypeTermForTypeInfo(input)}>>"
+
+        (baseClass,
+          s"Object select($inputTypeTerm $input1Term)",
+          List(),
+          true)
+      } else if (clazz == classOf[PatternFlatSelectFunction[_, _]]) {
+        val baseClass = classOf[PatternFlatSelectFunction[_, _]]
+        val inputTypeTerm =
+          s"java.util.Map<String, 
java.util.List<${boxedTypeTermForTypeInfo(input)}>>"
+
+        (baseClass,
+          s"void flatSelect($inputTypeTerm $input1Term, $collectorTypeTerm 
$collectorTerm)",
+          List(),
+          true)
+      } else {
+        throw new CodeGenException("Unsupported Function.")
+      }
+
+    val extendsKeyword = if (isInterface) "implements" else "extends"
+    val funcCode = j"""
+      |public class $funcName $extendsKeyword 
${functionClass.getCanonicalName} {
+      |
+      |  ${reuseMemberCode()}
+      |
+      |  public $funcName() throws Exception {
+      |    ${reuseInitCode()}
+      |  }
+      |
+      |  @Override
+      |  public $signature throws Exception {
+      |    ${inputStatements.mkString("\n")}
+      |    ${reusePerRecordCode()}
+      |    ${reuseInputUnboxingCode()}
+      |    $bodyCode
+      |  }
+      |}
+    """.stripMargin
+
+    GeneratedFunction(funcName, returnType, funcCode)
+  }
+
+  def generatePartitionKeyAccess(
+    partitionKey: RexInputRef
+  ) : GeneratedExpression = {
+    // extracts partition keys from any element of the match
+    val eventNameTerm = newName("event")
+    val eventTypeTerm = boxedTypeTermForTypeInfo(input)
+
+    val keyAccess = generateFieldAccess(input, eventNameTerm, 
partitionKey.getIndex)
+
+    val keyCode = s"""
+       |$eventTypeTerm $eventNameTerm = null;
+       |for (java.util.Map.Entry entry : $input1Term.entrySet()) {
+       |  java.util.List<$eventTypeTerm> value = 
(java.util.List<$eventTypeTerm>) entry.getValue();
+       |  if (value != null && value.size() > 0) {
+       |    $eventNameTerm = ($eventTypeTerm) value.get(0);
+       |    break;
+       |  }
+       |}
+       |
+       |${keyAccess.code}
+       """.stripMargin
+
+    keyAccess.copy(code = keyCode)
+  }
+
+  def generateOneRowPerMatchExpression(
+    partitionKeys: util.List[RexNode],
+    measures: util.Map[String, RexNode],
+    returnType: RowSchema
+  ): GeneratedExpression = {
+    // For "ONE ROW PER MATCH", the output columns include:
+    // 1) the partition columns;
+    // 2) the columns defined in the measures clause.
+    val resultExprs =
+      partitionKeys.asScala.map { case inputRef: RexInputRef =>
+        generatePartitionKeyAccess(inputRef)
+      } ++ returnType.fieldNames.filter(measures.containsKey(_)).map { 
fieldName =>
+        generateExpression(measures.get(fieldName))
+      }
+
+    generateResultExpression(
+      resultExprs,
+      returnType.typeInfo,
+      returnType.fieldNames)
+  }
+
+  override def visitCall(call: RexCall): GeneratedExpression = {
+    call.getOperator match {
+      case PREV | NEXT =>
+        val countLiteral = call.operands.get(1).asInstanceOf[RexLiteral]
+        val count = countLiteral.getValueAs(classOf[JLong])
+        if (count != 0) {
+          throw new TableException("Flink does not support physical offsets 
within partition.")
 
 Review comment:
   No we do not support physical offsets at all. Physical offset index elements 
independently from which rows were matched, e.g. you can index to before the 
start of a match. We do not have access to such elements.
   
   The `if` clause here is only because calcite translates every PRV into 
`PREV` call.

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> Support the basic functionality of MATCH_RECOGNIZE
> --------------------------------------------------
>
>                 Key: FLINK-7062
>                 URL: https://issues.apache.org/jira/browse/FLINK-7062
>             Project: Flink
>          Issue Type: Sub-task
>          Components: CEP, Table API &amp; SQL
>            Reporter: Dian Fu
>            Assignee: Dian Fu
>            Priority: Major
>              Labels: pull-request-available
>
> In this JIRA, we will support the basic functionality of {{MATCH_RECOGNIZE}} 
> in Flink SQL API which includes the support of syntax {{MEASURES}}, 
> {{PATTERN}} and {{DEFINE}}. This would allow users write basic cep use cases 
> with SQL like the following example:
> {code}
> SELECT T.aid, T.bid, T.cid
> FROM MyTable
> MATCH_RECOGNIZE (
>   MEASURES
>     A.id AS aid,
>     B.id AS bid,
>     C.id AS cid
>   PATTERN (A B C)
>   DEFINE
>     A AS A.name = 'a',
>     B AS B.name = 'b',
>     C AS C.name = 'c'
> ) AS T
> {code}



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