Github user julianhyde commented on a diff in the pull request:
https://github.com/apache/drill/pull/169#discussion_r40465777
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/physical/LimitUnionExchangeTransposeRule.java
---
@@ -0,0 +1,64 @@
+/**
+ * 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.physical;
+
+import org.apache.calcite.plan.RelOptRule;
+import org.apache.calcite.plan.RelOptRuleCall;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rex.RexLiteral;
+import org.apache.calcite.rex.RexNode;
+import org.apache.drill.exec.planner.logical.RelOptHelper;
+
+import java.math.BigDecimal;
+
+public class LimitUnionExchangeTransposeRule extends Prule{
+ public static final RelOptRule INSTANCE = new
LimitUnionExchangeTransposeRule();
+
+ private LimitUnionExchangeTransposeRule() {
+ super(RelOptHelper.some(LimitPrel.class,
RelOptHelper.any(UnionExchangePrel.class)), "LimitUnionExchangeTransposeRule");
+ }
+
+ @Override
+ public boolean matches(RelOptRuleCall call) {
+ final LimitPrel limit = (LimitPrel) call.rel(0);
+
+ return !limit.isPushDown();
+ }
+
+ @Override
+ public void onMatch(RelOptRuleCall call) {
+ final LimitPrel limit = (LimitPrel) call.rel(0);
+ final UnionExchangePrel unionExchangePrel = (UnionExchangePrel)
call.rel(1);
+
+ RelNode child = unionExchangePrel.getInput();
+
+ final int offset = limit.getOffset() != null ? Math.max(0,
RexLiteral.intValue(limit.getOffset())) : 0;
+ final int fetch = limit.getFetch() != null? Math.max(0,
RexLiteral.intValue(limit.getFetch())) : 0;
--- End diff --
@hsuanyi There are several changes going into Calcite for optimizing
limits. See https://issues.apache.org/jira/browse/CALCITE-831 and re-use those
rules in drill if applicable.
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