/**
* 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.drill.exec.planner.logical.RelOptHelper;
import org.apache.calcite.plan.RelOptRule;
import org.apache.calcite.plan.RelOptRuleCall;
import org.apache.calcite.rex.RexLiteral;
public class PushLimitToTopN extends Prule{
public static final RelOptRule INSTANCE = new PushLimitToTopN();
private PushLimitToTopN() {
super(RelOptHelper.some(LimitPrel.class, RelOptHelper.some(SingleMergeExchangePrel.class, RelOptHelper.any(SortPrel.class))), "PushLimitToTopN");
}
@Override
public void onMatch(RelOptRuleCall call) {
final LimitPrel limit = (LimitPrel) call.rel(0);
final SingleMergeExchangePrel smex = (SingleMergeExchangePrel) call.rel(1);
final SortPrel sort = (SortPrel) call.rel(2);
// First offset to include into results (inclusive). Null implies it is starting from offset 0
int offset = limit.getOffset() != null ? Math.max(0, RexLiteral.intValue(limit.getOffset())) : 0;
int fetch = limit.getFetch() != null? Math.max(0, RexLiteral.intValue(limit.getFetch())) : 0;
final TopNPrel topN = new TopNPrel(limit.getCluster(), sort.getTraitSet(), sort.getInput(), offset + fetch, sort.getCollation());
final LimitPrel newLimit = new LimitPrel(limit.getCluster(), limit.getTraitSet(),
new SingleMergeExchangePrel(smex.getCluster(), smex.getTraitSet(), topN, sort.getCollation()),
limit.getOffset(), limit.getFetch());
call.transformTo(newLimit);
}
}