/*
* 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 org.teiid.query.sql.LanguageObject;
import org.teiid.query.sql.LanguageVisitor;
import org.teiid.query.sql.visitor.SQLStringVisitor;
/**
* This class represents a join type.
* Outer joins will put nulls on the outer side for non-matches. "Cross" joins
* have no criteria and are a cross product of all rows in each table. To use
* a JoinType, you should not (and cannot) construct the object - rather you
* should use the provided static constants.
*/
public class JoinType implements LanguageObject {
// Constants defining join type - users will construct these
/** Represents an inner join: a INNER JOIN b */
public static final JoinType JOIN_INNER = new JoinType(0, false);
/** Represents a right outer join: a RIGHT OUTER JOIN b */
public static final JoinType JOIN_RIGHT_OUTER = new JoinType(1, true);
/** Represents a left outer join: a LEFT OUTER JOIN b */
public static final JoinType JOIN_LEFT_OUTER = new JoinType(2, true);
/** Represents a full outer join: a FULL OUTER JOIN b */
public static final JoinType JOIN_FULL_OUTER = new JoinType(3, true);
/** Represents a cross join: a CROSS JOIN b */
public static final JoinType JOIN_CROSS = new JoinType(4, false);
/** Represents a union join: a UNION JOIN b - not used after rewrite */
public static final JoinType JOIN_UNION = new JoinType(5, true);
/** internal SEMI Join type */
public static final JoinType JOIN_SEMI = new JoinType(6, false);
/** internal ANTI SEMI Join type */
public static final JoinType JOIN_ANTI_SEMI = new JoinType(7, true);
private int type;
private boolean outer;
/**
* Construct a join type object. This is private and is only called by
* the static constant objects in this class.
* @param type Type code for object
*/
private JoinType(int type, boolean outer) {
this.type = type;
this.outer = outer;
}
/**
* Used only for comparison during equals, not by users of this class
* @return Type code for object
*/
int getTypeCode() {
return this.type;
}
/**
* To switch directions from left to right or right to left. Joins
* that are not LEFT OUTER or RIGHT OUTER are returned unchanged.
* @return New JoinType constant for the reverse join type
*/
public JoinType getReverseType() {
if(this.equals(JOIN_RIGHT_OUTER)) {
return JOIN_LEFT_OUTER;
} else if(this.equals(JOIN_LEFT_OUTER)) {
return JOIN_RIGHT_OUTER;
}
return this;
}
/**
* Check if this join type is an outer join.
* @return True if left/right/full outer, false if inner/cross
*/
public boolean isOuter() {
return outer;
}
/**
* Override Object.equals() to compare objects
* @param other Other object
* @return True if equal
*/
public boolean equals(Object other) {
if(this == other) {
return true;
}
if(! (other instanceof JoinType)) {
return false;
}
return ((JoinType)other).getTypeCode() == this.type;
}
public void acceptVisitor(LanguageVisitor visitor) {
visitor.visit(this);
}
/**
* Get hash code for this type
* @return Hash code
*/
public int hashCode() {
return this.type;
}
/**
* Class is immutable, so clone can just return the same class
* @return Same object - these objects are immutable
*/
public Object clone() {
return this;
}
/**
* Returns a string representation of an instance of this class.
* @return String representation of object
*/
public String toString() {
return SQLStringVisitor.getSQLString(this);
}
}