Github user chaithu14 commented on a diff in the pull request:
https://github.com/apache/incubator-apex-malhar/pull/113#discussion_r46111198
--- Diff:
library/src/main/java/com/datatorrent/lib/join/AbstractJoinOperator.java ---
@@ -0,0 +1,341 @@
+/*
+ * Copyright (c) 2014 DataTorrent, Inc. ALL Rights Reserved.
+ *
+ * Licensed 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 com.datatorrent.lib.join;
+
+import java.lang.reflect.Array;
+import java.util.ArrayList;
+import java.util.Calendar;
+import java.util.List;
+
+import org.apache.hadoop.classification.InterfaceStability.Evolving;
+
+import com.datatorrent.api.Context;
+import com.datatorrent.api.DefaultInputPort;
+import com.datatorrent.api.DefaultOutputPort;
+import com.datatorrent.api.Operator;
+import com.datatorrent.api.annotation.InputPortFieldAnnotation;
+import com.datatorrent.common.util.BaseOperator;
+
+/**
+ * <p>
+ * This is the base implementation of join operator. Operator receives
tuples from multiple streams,
+ * applies the join operation based on constraint and emit the joined
value.
+ * Subclasses should provide implementation to
createOutputTuple,copyValue, getKeyValue, getTime methods.
+ *
+ * <b>Properties:</b><br>
+ * <b>expiryTime</b>: Expiry time for stored tuples<br>
+ * <b>includeFieldStr</b>: List of comma separated fields to be added to
the output tuple.
+ * Ex: Field1,Field2;Field3,Field4<br>
+ * <b>keyFields</b>: List of comma separated key field for both the
streams. Ex: Field1,Field2<br>
+ * <b>timeFields</b>: List of comma separated time field for both the
streams. Ex: Field1,Field2<br>
--- End diff --
Join operator is time based. timeField specifies the field of tuple which
has the time.
For example, One input port receives customer details and the other port
receives Order details.
Schema for the Customer be in the form of <ID, Name, RTime>
Schema for the Order be in the form of <OID, OTime, CID, Amount>
Now, Join the tuples of Customer and Order streams where Customer.ID =
Order.CID and the constraint is matched tuples must have timestamp within 5
minutes.
Here, key Fields = ID, CID and Time Fields = RTime, OTime
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