exec/java-exec/src/main/java/org/apache/drill/exec/expr/HoldingContainerExpression.java

/*
 * 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.expr;

import java.util.Collections;
import java.util.Iterator;

import org.apache.drill.common.expression.ExpressionPosition;
import org.apache.drill.common.expression.LogicalExpression;
import org.apache.drill.common.expression.visitors.ExprVisitor;
import org.apache.drill.common.types.TypeProtos.MajorType;
import org.apache.drill.exec.expr.ClassGenerator.HoldingContainer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Wrapper around a representation of a "Holder" to represent that
 * Holder as an expression. Whether this expression represents a
 * declaration, initialization, or reference (use) of the holder
 * depends on the visitor applied to this expression.
 * <p>
 * This expression class is a run-time implementation detail; it
 * shows up in the "unknown" bucket within the visitor, where it
 * must be parsed out using <code>instanceof</code> (or assumed.)
 */
public class HoldingContainerExpression implements LogicalExpression{
  static final Logger logger = LoggerFactory.getLogger(HoldingContainerExpression.class);

  final HoldingContainer container;

  public HoldingContainerExpression(HoldingContainer container) {
    this.container = container;
  }

  @Override
  public Iterator<LogicalExpression> iterator() {
    return Collections.emptyIterator();
  }

  @Override
  public MajorType getMajorType() {
    return container.getMajorType();
  }

  @Override
  public <T, V, E extends Exception> T accept(ExprVisitor<T, V, E> visitor, V value) throws E {
    return visitor.visitUnknown(this, value);
  }

  public HoldingContainer getContainer() {
    return container;
  }

  @Override
  public ExpressionPosition getPosition() {
    return ExpressionPosition.UNKNOWN;
  }

  @Override
  public int getSelfCost() {
    return 0;  // TODO
  }

  @Override
  public int getCumulativeCost() {
    return 0; // TODO
  }

  @Override
  public String toString() {
    return container.toString();
  }
}