/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hp.hpl.jena.sdb.core.sqlnode;
import java.util.ArrayList;
import java.util.List;
import com.hp.hpl.jena.sdb.core.sqlexpr.SqlColumn;
import com.hp.hpl.jena.sdb.shared.SDBInternalError;
// Unused - see SqlSelectBlock
public class SqlProject extends SqlNodeBase1
{
// Development:
// + SqlRename is an alias and just SqlProject of pre-calculated
// columns because SQL uses SELECT for both.
// + SqlCoalesce is a SqlProject with a COALESCE function
List <ColAlias> cols = null ;
// ---- Factory methods
/** make sure this node is a projection */
// This is not quite SqlSelectBlock.
/*public*/private static SqlNode project(SqlNode sqlNode)
{
return project(sqlNode, null) ;
}
/** make sure this node is a projection and add a column */
/*public*/private static SqlNode project(SqlNode sqlNode, SqlColumn col, String colOutName)
{
SqlColumn asCol = new SqlColumn(null, colOutName) ;
ColAlias colAlias = new ColAlias(col, asCol) ;
return SqlProject.project(sqlNode, colAlias) ;
}
/** make sure this node is a projection and add a column */
/*public*/public static SqlNode project(SqlNode sqlNode, ColAlias col)
{
// Not if to be left to the bridge.
//return SqlSelectBlock.project(sqlNode, col) ;
SqlProject p = ensure(sqlNode) ;
if ( col != null )
{
verify(p, col) ;
col.check(sqlNode.getAliasName()) ;
p.cols.add(col) ;
}
return p ;
}
private static void verify(SqlProject p, ColAlias col)
{
String newColName = col.getAlias().getColumnName() ;
for ( ColAlias a : p.getCols() )
if ( a.getAlias().getColumnName().equals(newColName) )
throw new SDBInternalError("Attempt to use same alias twice") ;
}
private static SqlProject ensure(SqlNode sqlNode)
{
if ( sqlNode.isProject() )
return sqlNode.asProject() ;
else
return new SqlProject(sqlNode) ;
}
// ----
private SqlProject(SqlNode sqlNode)
{ this(sqlNode, new ArrayList<ColAlias>()) ; }
private SqlProject(SqlNode sqlNode, List<ColAlias> cols)
{
super(null, sqlNode) ;
this.cols = cols ;
}
@Override
public boolean isProject() { return true ; }
@Override
public SqlProject asProject() { return this ; }
@Override
public boolean usesColumn(SqlColumn c) { return cols.contains(c) ; }
public List<ColAlias> getCols() { return cols ; }
@Override
public void visit(SqlNodeVisitor visitor)
{ throw new SDBInternalError("SqlProject.visit") ; }
//{ visitor.visit(this) ; }
@Override
public SqlNode apply(SqlTransform transform, SqlNode subNode)
{ throw new SDBInternalError("SqlProject.apply") ; }
//{ return transform.transform(this, subNode) ; }
@Override
public SqlNode copy(SqlNode subNode)
{
return new SqlProject(subNode, this.getCols()) ;
}
}