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package com.salesforce.phoenix.compile;
import java.util.Iterator;
import java.util.Map;
import com.google.common.collect.Maps;
import com.salesforce.phoenix.expression.Expression;
/**
*
* Class to manage list of expressions inside of a select statement by
* deduping them.
*
* @author jtaylor
* @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();
}
}