/*
* JBoss, Home of Professional Open Source.
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership. Some portions may be licensed
* to Red Hat, Inc. under one or more contributor license agreements.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301 USA.
*/
package org.teiid.query.sql.lang;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import org.teiid.core.util.EquivalenceUtil;
import org.teiid.core.util.HashCodeUtil;
import org.teiid.query.QueryPlugin;
import org.teiid.query.sql.LanguageObject;
import org.teiid.query.sql.LanguageVisitor;
import org.teiid.query.sql.symbol.Expression;
import org.teiid.query.sql.visitor.SQLStringVisitor;
/**
* This class represents the GROUP BY clause of a query, which defines the expressions
* that should be used for grouping the results of the query. The groups
* produced in the query are grouped on all symbols listed contained in the
* GROUP BY clause. The GROUP BY clause may not contain aliased elements,
* expressions, or constants.
*/
public class GroupBy implements LanguageObject {
/** The set of expressions for the data elements to be group. */
private List symbols; // List<Expression>
// =========================================================================
// C O N S T R U C T O R S
// =========================================================================
/**
* Constructs a default instance of this class.
*/
public GroupBy() {
symbols = new ArrayList();
}
/**
* Constructs an instance of this class from an ordered set of symbols.
* @param symbols The ordered list of {@link org.teiid.query.sql.symbol.ElementSymbol}s
*/
public GroupBy( List symbols ) {
this.symbols = new ArrayList( symbols );
}
// =========================================================================
// M E T H O D S
// =========================================================================
/**
* Returns the number of symbols in the GROUP BY
* @return Count of the number of symbols in GROUP BY
*/
public int getCount() {
return symbols.size();
}
/**
* Returns an ordered list of the symbols in the GROUP BY
* @return List of {@link org.teiid.query.sql.symbol.ElementSymbol}s
*/
public List getSymbols() {
return symbols;
}
/**
* Adds a new symbol to the list of symbols.
* @param symbol Symbol to add to GROUP BY
*/
public void addSymbol( Expression symbol ) {
if(symbol != null) {
symbols.add(symbol);
}
}
/**
* Replaces the existing set of symbols with a new collection of symbols
* @param symbols Collection of {@link org.teiid.query.sql.symbol.ElementSymbol}s
* to replace current symbols with
*/
public void replaceSymbols( Collection symbols ) {
if(symbols == null) {
throw new IllegalArgumentException(QueryPlugin.Util.getString("ERR.015.010.0003")); //$NON-NLS-1$
}
this.symbols = new ArrayList(symbols);
}
public void acceptVisitor(LanguageVisitor visitor) {
visitor.visit(this);
}
// =========================================================================
// O V E R R I D D E N O B J E C T M E T H O D S
// =========================================================================
/**
* Return a deep copy of this object
* @return Deep copy of object
*/
public Object clone() {
List thisSymbols = getSymbols();
List copySymbols = new ArrayList(thisSymbols.size());
Iterator iter = thisSymbols.iterator();
while(iter.hasNext()) {
Expression es = (Expression) iter.next();
copySymbols.add(es.clone());
}
return new GroupBy(copySymbols);
}
/**
* Compare two GroupBys for equality. Order is important in the comparison.
* @param obj Other object
* @return True if equal
*/
public boolean equals(Object obj) {
if(obj == this) {
return true;
}
if(!(obj instanceof GroupBy)) {
return false;
}
return EquivalenceUtil.areEqual(getSymbols(), ((GroupBy)obj).getSymbols());
}
/**
* Get hashcode for GroupBy. WARNING: The hash code relies on the variables
* in the group by, so changing the variables will change the hash code, causing
* a group by to be lost in a hash structure. Do not hash a GroupBy if you plan
* to change it.
* @return Hash code for object
*/
public int hashCode() {
return HashCodeUtil.hashCode(0, getSymbols());
}
/**
* Returns a string representation of an instance of this class.
* @return String representation of object
*/
public String toString() {
return SQLStringVisitor.getSQLString(this);
}
} // END CLASS