org.apache.calcite.adapter.pig.PigRel Maven / Gradle / Ivy
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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.calcite.adapter.pig;
import org.apache.calcite.plan.Convention;
import org.apache.calcite.rel.RelNode;
import java.util.ArrayList;
import java.util.List;
/**
* Relational expression that uses the Pig calling convention.
*/
public interface PigRel extends RelNode {
/**
* Converts this node to a Pig Latin statement.
*/
void implement(Implementor implementor);
// String getPigRelationAlias();
//
// String getFieldName(int index);
/** Calling convention for relational operations that occur in Pig. */
Convention CONVENTION = new Convention.Impl("PIG", PigRel.class);
/**
* Callback for the implementation process that converts a tree of
* {@link PigRel} nodes into complete Pig Latin script.
*/
class Implementor {
/**
* An ordered list of Pig Latin statements.
*
* See
*
* Pig Latin reference.
*/
private final List statements = new ArrayList<>();
public String getTableName(RelNode input) {
final List qualifiedName = input.getTable().getQualifiedName();
return qualifiedName.get(qualifiedName.size() - 1);
}
public String getPigRelationAlias(RelNode input) {
return getTableName(input);
}
public String getFieldName(RelNode input, int index) {
return input.getRowType().getFieldList().get(index).getName();
}
public void addStatement(String statement) {
statements.add(statement);
}
public void visitChild(int ordinal, RelNode input) {
assert ordinal == 0;
((PigRel) input).implement(this);
}
public List getStatements() {
return statements;
}
public String getScript() {
return String.join("\n", statements);
}
}
}