/*
* Copyright Aduna (http://www.aduna-software.com/) (c) 2008.
*
* Licensed under the Aduna BSD-style license.
*/
package org.openrdf.sail.rdbms.algebra.factories;
import static org.openrdf.sail.rdbms.algebra.base.SqlExprSupport.sqlNull;
import static org.openrdf.sail.rdbms.algebra.base.SqlExprSupport.str;
import static org.openrdf.sail.rdbms.algebra.base.SqlExprSupport.unsupported;
import org.openrdf.model.BNode;
import org.openrdf.model.Value;
import org.openrdf.query.algebra.Datatype;
import org.openrdf.query.algebra.Lang;
import org.openrdf.query.algebra.MathExpr;
import org.openrdf.query.algebra.QueryModelNode;
import org.openrdf.query.algebra.Str;
import org.openrdf.query.algebra.ValueConstant;
import org.openrdf.query.algebra.ValueExpr;
import org.openrdf.query.algebra.Var;
import org.openrdf.query.algebra.helpers.QueryModelVisitorBase;
import org.openrdf.sail.rdbms.algebra.BNodeColumn;
import org.openrdf.sail.rdbms.algebra.SqlNull;
import org.openrdf.sail.rdbms.algebra.StringValue;
import org.openrdf.sail.rdbms.algebra.base.SqlExpr;
import org.openrdf.sail.rdbms.exceptions.UnsupportedRdbmsOperatorException;
/**
* BNode expression factory - creates a {@link BNodeColumn} or a
* {@link StringValue} of the BNode ID.
*
* @author James Leigh
*/
public class BNodeExprFactory extends QueryModelVisitorBase<UnsupportedRdbmsOperatorException> {
protected SqlExpr result;
public SqlExpr createBNodeExpr(ValueExpr expr)
throws UnsupportedRdbmsOperatorException
{
result = null;
if (expr == null) {
return new SqlNull();
}
expr.visit(this);
if (result == null) {
return new SqlNull();
}
return result;
}
@Override
public void meet(Datatype node) {
result = sqlNull();
}
@Override
public void meet(Lang node)
throws UnsupportedRdbmsOperatorException
{
result = sqlNull();
}
@Override
public void meet(MathExpr node)
throws UnsupportedRdbmsOperatorException
{
result = sqlNull();
}
@Override
public void meet(Str node) {
result = sqlNull();
}
@Override
public void meet(ValueConstant vc) {
result = valueOf(vc.getValue());
}
@Override
public void meet(Var var) {
if (var.getValue() == null) {
result = new BNodeColumn(var);
}
else {
result = valueOf(var.getValue());
}
}
@Override
protected void meetNode(QueryModelNode arg)
throws UnsupportedRdbmsOperatorException
{
throw unsupported(arg);
}
private SqlExpr valueOf(Value value) {
if (value instanceof BNode) {
return str(((BNode)value).stringValue());
}
return sqlNull();
}
}