Github user hnfgns commented on a diff in the pull request:
https://github.com/apache/drill/pull/368#discussion_r61491435
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/contrib/SimpleParallelizerMultiPlans.java
---
@@ -0,0 +1,228 @@
+/**
+ * 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.drill.exec.planner.fragment.contrib;
+
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
+
+import org.apache.drill.common.exceptions.ExecutionSetupException;
+import org.apache.drill.common.util.DrillStringUtils;
+import org.apache.drill.exec.ops.QueryContext;
+import org.apache.drill.exec.physical.base.Exchange;
+import org.apache.drill.exec.physical.base.FragmentRoot;
+import org.apache.drill.exec.physical.base.PhysicalOperator;
+import org.apache.drill.exec.planner.PhysicalPlanReader;
+import org.apache.drill.exec.planner.fragment.Fragment;
+import org.apache.drill.exec.planner.fragment.PlanningSet;
+import org.apache.drill.exec.planner.fragment.SimpleParallelizer;
+import org.apache.drill.exec.planner.fragment.Wrapper;
+import
org.apache.drill.exec.planner.fragment.Materializer.IndexedFragmentNode;
+import org.apache.drill.exec.proto.BitControl.PlanFragment;
+import org.apache.drill.exec.proto.BitControl.QueryContextInformation;
+import org.apache.drill.exec.proto.CoordinationProtos.DrillbitEndpoint;
+import org.apache.drill.exec.proto.ExecProtos.FragmentHandle;
+import org.apache.drill.exec.proto.UserBitShared.QueryId;
+import org.apache.drill.exec.rpc.user.UserSession;
+import org.apache.drill.exec.server.options.OptionList;
+import org.apache.drill.exec.work.QueryWorkUnit;
+import org.apache.drill.exec.work.foreman.ForemanSetupException;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.Lists;
+
+/**
+ * SimpleParallelizerMultiPlans class is an extension to SimpleParallelizer
+ * to help with getting PlanFragments for split plan.
+ * Split plan is essentially ability to create multiple Physical Operator
plans from original Physical Operator plan
+ * to be able to run plans separately.
+ * Moving functionality specific to splitting the plan to this class
+ * allows not to pollute parent class with non-authentic functionality
+ *
+ */
+public class SimpleParallelizerMultiPlans extends SimpleParallelizer {
+
+ static final org.slf4j.Logger logger =
org.slf4j.LoggerFactory.getLogger(SimpleParallelizerMultiPlans.class);
+
+ public SimpleParallelizerMultiPlans(QueryContext context) {
+ super(context);
+ }
+
+ /**
+ * Create multiple physical plans from original query planning, it will
allow execute them eventually independently
+ * @param options
+ * @param foremanNode
+ * @param queryId
+ * @param activeEndpoints
+ * @param reader
+ * @param rootFragment
+ * @param session
+ * @param queryContextInfo
+ * @return
+ * @throws ExecutionSetupException
+ */
+ public List<QueryWorkUnit> getSplitFragments(OptionList options,
DrillbitEndpoint foremanNode, QueryId queryId,
+ Collection<DrillbitEndpoint> activeEndpoints, PhysicalPlanReader
reader, Fragment rootFragment,
+ UserSession session, QueryContextInformation queryContextInfo)
throws ExecutionSetupException {
+
+ final PlanningSet planningSet = getFragmentsHelper(activeEndpoints,
rootFragment);
+
+ return generateWorkUnits(
+ options, foremanNode, queryId, reader, rootFragment, planningSet,
session, queryContextInfo);
+ }
+
+ /**
+ * Split plan into multiple plans based on parallelization
+ * Ideally it is applicable only to plans with two major fragments:
Screen and UnionExchange
+ * But there could be cases where we can remove even multiple exchanges
like in case of "order by"
--- End diff --
I am not comfortable with this statement. How do you drop exchange for
"order by" but still sort?
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