FatLittle commented on a change in pull request #1991: URL: https://github.com/apache/calcite/pull/1991#discussion_r451565232
########## File path: core/src/main/java/org/apache/calcite/rel/metadata/RelMdLowerBoundCost.java ########## @@ -0,0 +1,112 @@ +/* + * 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.calcite.rel.metadata; + +import org.apache.calcite.plan.RelOptCost; +import org.apache.calcite.plan.volcano.AbstractConverter; +import org.apache.calcite.plan.volcano.RelSubset; +import org.apache.calcite.plan.volcano.VolcanoPlanner; +import org.apache.calcite.rel.RelNode; +import org.apache.calcite.rel.metadata.BuiltInMetadata.LowerBoundCost; +import org.apache.calcite.util.BuiltInMethod; + +/** + * Default implementations of the + * {@link BuiltInMetadata.LowerBoundCost} + * metadata provider for the standard algebra. + */ +public class RelMdLowerBoundCost implements MetadataHandler<LowerBoundCost> { + + public static final RelMetadataProvider SOURCE = + ReflectiveRelMetadataProvider.reflectiveSource( + new RelMdLowerBoundCost(), BuiltInMethod.LOWER_BOUND_COST.method); + + //~ Constructors ----------------------------------------------------------- + + protected RelMdLowerBoundCost() {} + + //~ Methods ---------------------------------------------------------------- + + public MetadataDef<LowerBoundCost> getDef() { + return BuiltInMetadata.LowerBoundCost.DEF; + } + + public RelOptCost getLowerBoundCost(RelSubset subset, + RelMetadataQuery mq, VolcanoPlanner planner) { + + if (planner.isLogical(subset)) { + // currently only support physical, will improve in the future + return null; + } + + RelOptCost winner = subset.getWinnerCost(); + if (winner != null) { + // when this subset is fully optimized, just return the winner + return winner; + } + + // if group is not fully explored. Its properties like cardinality + // would get changed after exploration. So it cannot return a valid LB + if (!subset.isExplored()) { + return null; + } + + RelOptCost lowerBound = null; Review comment: resolved ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected]
