/**
* 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.common.logical.data;
import com.google.common.collect.Iterators;
import org.apache.drill.common.exceptions.ExpressionParsingException;
import org.apache.drill.common.expression.PathSegment;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonTypeName;
import org.apache.drill.common.logical.data.visitors.LogicalVisitor;
import java.util.Iterator;
@JsonTypeName("project")
public class Project extends SingleInputOperator {
private final NamedExpression[] selections;
@JsonCreator
public Project(@JsonProperty("projections") NamedExpression[] selections) {
this.selections = selections;
if(selections == null || selections.length == 0) throw new ExpressionParsingException("Project did not provide any projection selections. At least one projection must be provided.");
for (int i = 0; i < selections.length; i++) {
PathSegment segment = selections[i].getRef().getRootSegment();
CharSequence path = segment.getNameSegment().getPath();
if (!segment.isNamed() || !path.equals("output"))
throw new ExpressionParsingException(String.format(
"Outputs for projections always have to start with named path of output. First segment was named '%s' or was named [%s]", path, segment.isNamed()));
}
}
@JsonProperty("projections")
public NamedExpression[] getSelections() {
return selections;
}
@Override
public <T, X, E extends Throwable> T accept(LogicalVisitor<T, X, E> logicalVisitor, X value) throws E {
return logicalVisitor.visitProject(this, value);
}
@Override
public Iterator<LogicalOperator> iterator() {
return Iterators.singletonIterator(getInput());
}
}