/*
* 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 org.apache.directory.server.xdbm.search.impl;
import java.util.ArrayList;
import java.util.List;
import org.apache.directory.server.core.entry.ServerEntry;
import org.apache.directory.server.i18n.I18n;
import org.apache.directory.server.xdbm.IndexCursor;
import org.apache.directory.server.xdbm.Store;
import org.apache.directory.server.xdbm.search.Evaluator;
import org.apache.directory.shared.ldap.NotImplementedException;
import org.apache.directory.shared.ldap.filter.AndNode;
import org.apache.directory.shared.ldap.filter.ExprNode;
import org.apache.directory.shared.ldap.filter.NotNode;
import org.apache.directory.shared.ldap.filter.OrNode;
import org.apache.directory.shared.ldap.filter.ScopeNode;
import org.apache.directory.shared.ldap.filter.SearchScope;
/**
* Builds Cursors over candidates that satisfy a filter expression.
*
* @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
* @version $Rev: 917442 $
*/
public class CursorBuilder<ID>
{
/** The database used by this builder */
private Store<ServerEntry, ID> db = null;
/** Evaluator dependency on a EvaluatorBuilder */
private EvaluatorBuilder<ID> evaluatorBuilder;
/**
* Creates an expression tree enumerator.
*
* @param db database used by this enumerator
* @param evaluatorBuilder the evaluator builder
*/
public CursorBuilder( Store<ServerEntry, ID> db, EvaluatorBuilder<ID> evaluatorBuilder )
{
this.db = db;
this.evaluatorBuilder = evaluatorBuilder;
}
public <T> IndexCursor<?, ServerEntry, ID> build( ExprNode node ) throws Exception
{
switch ( node.getAssertionType() )
{
/* ---------- LEAF NODE HANDLING ---------- */
case APPROXIMATE:
return new ApproximateCursor<T, ID>( db, ( ApproximateEvaluator<T, ID> ) evaluatorBuilder.build( node ) );
case EQUALITY:
return new EqualityCursor<T, ID>( db, ( EqualityEvaluator<T, ID> ) evaluatorBuilder.build( node ) );
case GREATEREQ:
return new GreaterEqCursor<T, ID>( db, ( GreaterEqEvaluator<T, ID> ) evaluatorBuilder.build( node ) );
case LESSEQ:
return new LessEqCursor<T, ID>( db, ( LessEqEvaluator<T, ID> ) evaluatorBuilder.build( node ) );
case PRESENCE:
return new PresenceCursor<ID>( db, ( PresenceEvaluator<ID> ) evaluatorBuilder.build( node ) );
case SCOPE:
if ( ( ( ScopeNode ) node ).getScope() == SearchScope.ONELEVEL )
{
return new OneLevelScopeCursor<ID>( db,
( OneLevelScopeEvaluator<ServerEntry, ID> ) evaluatorBuilder.build( node ) );
}
else
{
return new SubtreeScopeCursor<ID>( db, ( SubtreeScopeEvaluator<ServerEntry, ID> ) evaluatorBuilder
.build( node ) );
}
case SUBSTRING:
return new SubstringCursor<ID>( db, ( SubstringEvaluator<ID> ) evaluatorBuilder.build( node ) );
/* ---------- LOGICAL OPERATORS ---------- */
case AND:
return buildAndCursor( ( AndNode ) node );
case NOT:
return new NotCursor<ID, ID>( db, evaluatorBuilder.build( ( ( NotNode ) node ).getFirstChild() ) );
case OR:
return buildOrCursor( ( OrNode ) node );
/* ---------- NOT IMPLEMENTED ---------- */
case ASSERTION:
case EXTENSIBLE:
throw new NotImplementedException();
default:
throw new IllegalStateException( I18n.err( I18n.ERR_260, node.getAssertionType() ) );
}
}
/**
* Creates a OrCursor over a disjunction expression branch node.
*
* @param node the disjunction expression branch node
* @return Cursor over candidates satisfying disjunction expression
* @throws Exception on db access failures
*/
private IndexCursor<?, ServerEntry, ID> buildOrCursor( OrNode node ) throws Exception
{
List<ExprNode> children = node.getChildren();
List<IndexCursor<? extends Object, ServerEntry, ID>> childCursors = new ArrayList<IndexCursor<?, ServerEntry, ID>>(
children.size() );
List<Evaluator<? extends ExprNode, ServerEntry, ID>> childEvaluators = new ArrayList<Evaluator<? extends ExprNode, ServerEntry, ID>>(
children.size() );
// Recursively create Cursors and Evaluators for each child expression node
for ( ExprNode child : children )
{
childCursors.add( build( child ) );
childEvaluators.add( evaluatorBuilder.build( child ) );
}
return new OrCursor( childCursors, childEvaluators );
}
/**
* Creates an AndCursor over a conjunction expression branch node.
*
* @param node a conjunction expression branch node
* @return Cursor over the conjunction expression
* @throws Exception on db access failures
*/
private IndexCursor<?, ServerEntry, ID> buildAndCursor( AndNode node ) throws Exception
{
int minIndex = 0;
long minValue = Long.MAX_VALUE;
//noinspection UnusedAssignment
long value = Long.MAX_VALUE;
/*
* We scan the child nodes of a branch node searching for the child
* expression node with the smallest scan count. This is the child
* we will use for iteration by creating a Cursor over its expression.
*/
final List<ExprNode> children = node.getChildren();
for ( int ii = 0; ii < children.size(); ii++ )
{
ExprNode child = children.get( ii );
Object count = child.get( "count" );
if ( count == null )
{
continue;
}
value = ( Long ) count;
minValue = Math.min( minValue, value );
if ( minValue == value )
{
minIndex = ii;
}
}
// Once found we build the child Evaluators minus the one for the minChild
ExprNode minChild = children.get( minIndex );
List<Evaluator<? extends ExprNode, ServerEntry, ID>> childEvaluators = new ArrayList<Evaluator<? extends ExprNode, ServerEntry, ID>>(
children.size() - 1 );
for ( ExprNode child : children )
{
if ( child == minChild )
{
continue;
}
childEvaluators.add( evaluatorBuilder.build( child ) );
}
// Do recursive call to build min child Cursor then create AndCursor
IndexCursor<?, ServerEntry, ID> childCursor = build( minChild );
return new AndCursor( childCursor, childEvaluators );
}
}