/*
* 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.symbol;
import java.util.concurrent.atomic.AtomicInteger;
import org.teiid.query.sql.LanguageVisitor;
import org.teiid.query.sql.lang.QueryCommand;
import org.teiid.query.sql.lang.SubqueryContainer;
import org.teiid.query.sql.visitor.SQLStringVisitor;
/**
* This is an Expression implementation that can be used in a SELECT clause.
* It has a subquery Command which must only produce exactly one
* value (or an Exception will result during query processing). It's type
* will be the type of the one symbol to be produced. In theory an instance
* of this could be used wherever an Expression is legal, but it is
* specifically needed for the SELECT clause.
*/
public class ScalarSubquery implements Expression, SubqueryContainer<QueryCommand>, ContextReference {
private static AtomicInteger ID = new AtomicInteger();
private QueryCommand command;
private Class<?> type;
private int hashCode;
private String id = "$sc/id" + ID.getAndIncrement(); //$NON-NLS-1$
private boolean shouldEvaluate;
/**
* Default constructor
*/
ScalarSubquery() {
super();
}
public ScalarSubquery(QueryCommand subqueryCommand){
this.setCommand(subqueryCommand);
}
public boolean shouldEvaluate() {
return shouldEvaluate;
}
public void setShouldEvaluate(boolean shouldEvaluate) {
this.shouldEvaluate = shouldEvaluate;
}
@Override
public String getContextSymbol() {
return id;
}
@Override
public Expression getValueExpression() {
return null;
}
/**
* @see org.teiid.query.sql.symbol.Expression#isResolved()
*/
public boolean isResolved() {
return (this.getType() != null);
}
/**
* @see org.teiid.query.sql.symbol.Expression#getType()
*/
public Class<?> getType() {
if (this.type == null){
Expression symbol = this.command.getProjectedSymbols().iterator().next();
this.type = symbol.getType();
}
//may still be null if this.command wasn't resolved
return this.type;
}
/**
* Set type of ScalarSubquery
* @param type New type
*/
public void setType(Class<?> type) {
this.type = type;
}
public QueryCommand getCommand() {
return this.command;
}
/**
* Sets the command. Also modifies the hash code of this object, so
* caution should be used in using this method.
*/
public void setCommand(QueryCommand command){
this.command = command;
this.hashCode = command.hashCode();
}
public void acceptVisitor(LanguageVisitor visitor) {
visitor.visit(this);
}
/**
* Compare this ScalarSubquery to another ScalarSubquery for equality.
* @param obj Other object
* @return true if objects are equal
*/
public boolean equals(Object obj) {
if(this == obj) {
return true;
}
if(! (obj instanceof ScalarSubquery)) {
return false;
}
ScalarSubquery other = (ScalarSubquery) obj;
return other.getCommand().equals(this.getCommand());
}
/**
* Get hashcode for the object
* @return Hash code
*/
public int hashCode() {
return this.hashCode;
}
/**
* Returns a safe clone
* @see java.lang.Object#clone()
*/
public Object clone() {
QueryCommand copyCommand = null;
if(getCommand() != null) {
copyCommand = (QueryCommand) getCommand().clone();
}
ScalarSubquery clone = new ScalarSubquery(copyCommand);
//Don't invoke the lazy-loading getType()
clone.setType(this.type);
clone.shouldEvaluate = this.shouldEvaluate;
return clone;
}
/**
* Returns string representation of this object.
* @return String representing the object
*/
public String toString() {
return SQLStringVisitor.getSQLString(this);
}
}