Github user julianhyde commented on a diff in the pull request:
https://github.com/apache/drill/pull/193#discussion_r45012029
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/DrillDirectScanRel.java
---
@@ -0,0 +1,111 @@
+/**
+ * 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.logical;
+
+import com.google.common.collect.Iterators;
+import org.apache.calcite.plan.RelOptCluster;
+import org.apache.calcite.plan.RelTraitSet;
+import org.apache.calcite.rel.AbstractRelNode;
+import org.apache.calcite.rel.RelWriter;
+import org.apache.calcite.rel.type.RelDataType;
+import org.apache.drill.common.logical.data.LogicalOperator;
+import org.apache.drill.exec.physical.base.PhysicalOperator;
+import org.apache.drill.exec.planner.physical.DrillScanPrel;
+import org.apache.drill.exec.planner.physical.PhysicalPlanCreator;
+import org.apache.drill.exec.planner.physical.PlannerSettings;
+import org.apache.drill.exec.planner.physical.Prel;
+import org.apache.drill.exec.planner.physical.PrelUtil;
+import org.apache.drill.exec.planner.physical.visitor.PrelVisitor;
+import org.apache.drill.exec.record.BatchSchema;
+import org.apache.drill.exec.store.direct.DirectGroupScan;
+
+import java.io.IOException;
+import java.util.Iterator;
+
+/**
+ * Logical and physical RelNode representing a {@link DirectGroupScan}.
This is not backed by a {@link DrillTable},
+ * unlike {@link DrillScanRel}.
+ */
+public class DrillDirectScanRel extends AbstractRelNode implements
DrillScanPrel, DrillRel {
--- End diff --
Yeah, I think DrillDirectScanRel is a wrong turn for this functionality,
because you can't see that it is empty and reason about it. A DirectGroupScan
is a runtime thing, so shouldn't be floating around at planning time.
I notice that DrillValuesRel does not extend Values. If it did, it would
get all of the rules in PruneEmptyRules for free - pruning away Filter, Project
etc. on top of it.
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