/*
* 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.phoenix.compile;
import java.util.Iterator;
import java.util.Map;
import com.google.common.collect.Maps;
import org.apache.phoenix.expression.Expression;
/**
*
* Class to manage list of expressions inside of a select statement by
* deduping them.
*
*
* @since 0.1
*/
public class ExpressionManager {
// Use a Map instead of a Set because we need to get and return
// the existing Expression
private final Map<Expression, Expression> expressionMap;
public ExpressionManager() {
expressionMap = Maps.newHashMap();
}
/**
* Add the expression to the set of known expressions for the select
* clause. If the expression is already in the set, then the new one
* passed in is ignored.
* @param expression the new expression to add
* @return the new expression if not already present in the set and
* the existing one otherwise.
*/
public Expression addIfAbsent(Expression expression) {
Expression existingExpression = expressionMap.get(expression);
if (existingExpression == null) {
expressionMap.put(expression, expression);
return expression;
}
return existingExpression;
}
public int getExpressionCount() {
return expressionMap.size();
}
public Iterator<Expression> getExpressions() {
return expressionMap.keySet().iterator();
}
}