| /* |
| * 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 org.apache.directory.server.xdbm.IndexEntry; |
| import org.apache.directory.server.xdbm.AbstractIndexCursor; |
| import org.apache.directory.server.xdbm.IndexCursor; |
| import org.apache.directory.server.xdbm.search.Evaluator; |
| import org.apache.directory.server.core.cursor.InvalidCursorPositionException; |
| import org.apache.directory.server.core.entry.ServerEntry; |
| import org.apache.directory.shared.ldap.filter.ExprNode; |
| |
| import java.util.*; |
| |
| |
| /** |
| * A Cursor returning candidates satisfying a logical conjunction expression. |
| * |
| * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a> |
| * @version $Rev$ |
| */ |
| public class AndCursor<V> extends AbstractIndexCursor<V, ServerEntry> |
| { |
| private static final String UNSUPPORTED_MSG = |
| "AndCursors are not ordered and do not support positioning by element."; |
| private final IndexCursor<V,ServerEntry> wrapped; |
| private final List<Evaluator<? extends ExprNode, ServerEntry>> evaluators; |
| private boolean available = false; |
| |
| |
| public AndCursor( IndexCursor<V, ServerEntry> wrapped, |
| List<Evaluator<? extends ExprNode, ServerEntry>> evaluators ) |
| { |
| this.wrapped = wrapped; |
| this.evaluators = optimize( evaluators ); |
| } |
| |
| |
| public boolean available() |
| { |
| return available; |
| } |
| |
| |
| public void beforeValue( Long id, V value ) |
| { |
| throw new UnsupportedOperationException( UNSUPPORTED_MSG ); |
| } |
| |
| |
| public void afterValue( Long id, V value ) |
| { |
| throw new UnsupportedOperationException( UNSUPPORTED_MSG ); |
| } |
| |
| |
| public void before( IndexEntry<V, ServerEntry> element ) throws Exception |
| { |
| throw new UnsupportedOperationException( UNSUPPORTED_MSG ); |
| } |
| |
| |
| public void after( IndexEntry<V, ServerEntry> element ) throws Exception |
| { |
| throw new UnsupportedOperationException( UNSUPPORTED_MSG ); |
| } |
| |
| |
| public void beforeFirst() throws Exception |
| { |
| wrapped.beforeFirst(); |
| available = false; |
| } |
| |
| |
| public void afterLast() throws Exception |
| { |
| wrapped.afterLast(); |
| available = false; |
| } |
| |
| |
| public boolean first() throws Exception |
| { |
| beforeFirst(); |
| return next(); |
| } |
| |
| |
| public boolean last() throws Exception |
| { |
| afterLast(); |
| return previous(); |
| } |
| |
| |
| public boolean previous() throws Exception |
| { |
| while ( wrapped.previous() ) |
| { |
| IndexEntry<?,ServerEntry> candidate = wrapped.get(); |
| if ( matches( candidate ) ) |
| { |
| return available = true; |
| } |
| } |
| |
| return available = false; |
| } |
| |
| |
| public boolean next() throws Exception |
| { |
| while ( wrapped.next() ) |
| { |
| IndexEntry<?,ServerEntry> candidate = wrapped.get(); |
| if ( matches( candidate ) ) |
| { |
| return available = true; |
| } |
| } |
| |
| return available = false; |
| } |
| |
| |
| public IndexEntry<V, ServerEntry> get() throws Exception |
| { |
| if ( available ) |
| { |
| return wrapped.get(); |
| } |
| |
| throw new InvalidCursorPositionException( "Cursor has not been positioned yet." ); |
| } |
| |
| |
| public boolean isElementReused() |
| { |
| return wrapped.isElementReused(); |
| } |
| |
| |
| public void close() throws Exception |
| { |
| super.close(); |
| wrapped.close(); |
| } |
| |
| |
| /** |
| * TODO - duplicate code from AndEvaluator just make utility for this and |
| * for the same code in the OrEvaluator once done. |
| * |
| * Takes a set of Evaluators and copies then sorts them in a new list with |
| * increasing scan counts on their expression nodes. This is done to have |
| * the Evaluators with the least scan count which have the highest |
| * probability of rejecting a candidate first. That will increase the |
| * chance of shorting the checks on evaluators early so extra lookups and |
| * comparisons are avoided. |
| * |
| * @param unoptimized the unoptimized list of Evaluators |
| * @return optimized Evaluator list with increasing scan count ordering |
| */ |
| private List<Evaluator<? extends ExprNode,ServerEntry>> |
| optimize( List<Evaluator<? extends ExprNode,ServerEntry>> unoptimized ) |
| { |
| List<Evaluator<? extends ExprNode,ServerEntry>> optimized = |
| new ArrayList<Evaluator<? extends ExprNode,ServerEntry>>( unoptimized.size() ); |
| optimized.addAll( unoptimized ); |
| Collections.sort( optimized, new Comparator<Evaluator<?,ServerEntry>>() |
| { |
| public int compare( Evaluator<?, ServerEntry> e1, Evaluator<?, ServerEntry> e2 ) |
| { |
| long scanCount1 = ( Long ) e1.getExpression().get( "count" ); |
| long scanCount2 = ( Long ) e2.getExpression().get( "count" ); |
| |
| if ( scanCount1 == scanCount2 ) |
| { |
| return 0; |
| } |
| |
| /* |
| * We want the Evaluator with the smallest scan count first |
| * since this node has the highest probability of failing, or |
| * rather the least probability of succeeding. That way we |
| * can short the sub-expression evaluation process. |
| */ |
| if ( scanCount1 < scanCount2 ) |
| { |
| return -1; |
| } |
| |
| return 1; |
| } |
| }); |
| |
| return optimized; |
| } |
| |
| |
| private boolean matches( IndexEntry<?, ServerEntry> indexEntry ) throws Exception |
| { |
| for ( Evaluator<?,ServerEntry> evaluator : evaluators ) |
| { |
| if ( ! evaluator.evaluate( indexEntry ) ) |
| { |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| } |