[GitHub] [samza] atoomula commented on a change in pull request #1386: [SAMZA-2557] Adding support for nested rows access via dot path.

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atoomula commented on a change in pull request #1386:
URL: https://github.com/apache/samza/pull/1386#discussion_r448989230



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File path: samza-sql/src/main/java/org/apache/samza/sql/translator/MessageStreamCollector.java
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@@ -0,0 +1,214 @@
+/*
+ * 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.samza.sql.translator;
+
+import java.io.Closeable;
+import java.io.Serializable;
+import java.time.Duration;
+import java.util.ArrayDeque;
+import java.util.Collection;
+import java.util.Deque;
+import java.util.function.Function;
+import org.apache.samza.context.Context;
+import org.apache.samza.operators.KV;
+import org.apache.samza.operators.MessageStream;
+import org.apache.samza.operators.OutputStream;
+import org.apache.samza.operators.functions.AsyncFlatMapFunction;
+import org.apache.samza.operators.functions.FilterFunction;
+import org.apache.samza.operators.functions.FlatMapFunction;
+import org.apache.samza.operators.functions.JoinFunction;
+import org.apache.samza.operators.functions.MapFunction;
+import org.apache.samza.operators.functions.SinkFunction;
+import org.apache.samza.operators.functions.StreamTableJoinFunction;
+import org.apache.samza.operators.windows.Window;
+import org.apache.samza.operators.windows.WindowPane;
+import org.apache.samza.serializers.KVSerde;
+import org.apache.samza.serializers.Serde;
+import org.apache.samza.sql.data.SamzaSqlRelMessage;
+import org.apache.samza.table.Table;
+
+
+/**
+ * Collector of Map and Filter Samza Functions to collect call stack on the top of Remote table.
+ * This Collector will be used by Join operator and trigger it when applying the join function post lookup.
+ *
+ * Note that this is needed because the Remote Table can not expose a proper {@code MessageStream}.
+ * It is a work around to minimize the amount of code changes of the current Query Translator {@link org.apache.samza.sql.translator.QueryTranslator},
+ * But in an ideal world, we should use Calcite planner in conventional way we can combine function when via translation of RelNodes.

Review comment:
       I still do not get it. Why can't we use query optimization for remote tables and if we see a filter/projection between table (we can detect table vs stream in the optimizer rule) and join in the Calcite plan, push them up ?




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