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/*
* 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;
import org.apache.calcite.plan.Context;
import org.apache.calcite.plan.Contexts;
import org.apache.calcite.plan.RelOptCluster;
import org.apache.calcite.plan.RelOptSchema;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.RelFactories;
import org.apache.calcite.tools.RelBuilder;
import org.apache.calcite.tools.RelBuilderFactory;
import org.apache.calcite.util.Util;
public class DrillRelBuilder extends RelBuilder {
private final RelFactories.FilterFactory filterFactory;
protected DrillRelBuilder(Context context, RelOptCluster cluster, RelOptSchema relOptSchema) {
super(context, cluster, relOptSchema);
this.filterFactory =
Util.first(context.unwrap(RelFactories.FilterFactory.class),
RelFactories.DEFAULT_FILTER_FACTORY);
}
/**
* Original method {@link RelBuilder#empty} returns empty values rel.
* In the order to preserve data row types, filter with false predicate is created.
*/
@Override
public RelBuilder empty() {
// pops the frame from the stack and returns its relational expression
RelNode relNode = build();
// creates filter with false in the predicate
final RelNode filter = filterFactory.createFilter(relNode, cluster.getRexBuilder().makeLiteral(false));
push(filter);
return this;
}
/** Creates a {@link RelBuilderFactory}, a partially-created DrillRelBuilder.
* Just add a {@link RelOptCluster} and a {@link RelOptSchema} */
public static RelBuilderFactory proto(final Context context) {
return new RelBuilderFactory() {
public RelBuilder create(RelOptCluster cluster, RelOptSchema schema) {
return new DrillRelBuilder(context, cluster, schema);
}
};
}
/** Creates a {@link RelBuilderFactory} that uses a given set of factories. */
public static RelBuilderFactory proto(Object... factories) {
return proto(Contexts.of(factories));
}
}
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