| /* |
| * 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.lucene.codecs.uniformsplit; |
| |
| import java.io.IOException; |
| import org.apache.lucene.store.DataOutput; |
| import org.apache.lucene.util.Accountable; |
| import org.apache.lucene.util.BytesRef; |
| import org.apache.lucene.util.IOSupplier; |
| |
| /** |
| * Immutable stateless index dictionary kept in RAM. |
| * |
| * <p>Implementations must be immutable. |
| * |
| * <p>Use {@link IndexDictionary.Builder} to build the {@link IndexDictionary}. |
| * |
| * <p>Create a stateful {@link IndexDictionary.Browser} to seek a term in this {@link |
| * IndexDictionary} and get its corresponding block file pointer to the terms block file. |
| * |
| * <p>There is a single implementation of this interface, {@link FSTDictionary}. However this |
| * interface allows you to plug easily a new kind of index dictionary to experiment and improve the |
| * existing one. |
| * |
| * @lucene.experimental |
| */ |
| public interface IndexDictionary extends Accountable { |
| |
| /** |
| * Writes this dictionary to the provided output. |
| * |
| * @param blockEncoder The {@link BlockEncoder} for specific encoding of this index dictionary; or |
| * null if none. |
| */ |
| void write(DataOutput output, BlockEncoder blockEncoder) throws IOException; |
| |
| /** Creates a new {@link IndexDictionary.Browser}. */ |
| Browser browser() throws IOException; |
| |
| /** Builds an immutable {@link IndexDictionary}. */ |
| interface Builder { |
| |
| /** |
| * Adds a [block key - block file pointer] entry to the dictionary. |
| * |
| * <p>The Uniform Split technique adds block keys in the dictionary. See {@link BlockReader} and |
| * {@link TermBytes} for more info about block key and minimal distinguishing prefix (MDP). |
| * |
| * <p>All block keys are added in strictly increasing order of the block file pointers, this |
| * allows long encoding optimizations such as with {@link |
| * org.apache.lucene.util.fst.PositiveIntOutputs} for {@link org.apache.lucene.util.fst.FST}. |
| * |
| * @param blockKey The block key which is the minimal distinguishing prefix (MDP) of the first |
| * term of a block. |
| * @param blockFilePointer Non-negative file pointer to the start of the block in the block |
| * file. |
| */ |
| void add(BytesRef blockKey, long blockFilePointer) throws IOException; |
| |
| /** Builds the immutable {@link IndexDictionary} for the added entries. */ |
| IndexDictionary build() throws IOException; |
| } |
| |
| /** |
| * Stateful {@link IndexDictionary.Browser} to seek a term in this {@link IndexDictionary} and get |
| * its corresponding block file pointer in the block file. |
| */ |
| interface Browser { |
| |
| /** |
| * Seeks the given term in the {@link IndexDictionary} and returns its corresponding block file |
| * pointer. |
| * |
| * @return The block file pointer corresponding to the term if it matches exactly a block key in |
| * the dictionary. Otherwise the floor block key, which is the greatest block key present in |
| * the dictionary that is alphabetically preceding the searched term. Otherwise {@code -1} |
| * if there is no floor block key because the searched term precedes alphabetically the |
| * first block key of the dictionary. |
| */ |
| long seekBlock(BytesRef term) throws IOException; |
| } |
| |
| /** |
| * Supplier for a new stateful {@link Browser} created on the immutable {@link IndexDictionary}. |
| * |
| * <p>The immutable {@link IndexDictionary} is lazy loaded thread safely. This lazy loading allows |
| * us to load it only when {@link org.apache.lucene.index.TermsEnum#seekCeil} or {@link |
| * org.apache.lucene.index.TermsEnum#seekExact} are called (it is not loaded for a direct |
| * all-terms enumeration). |
| */ |
| interface BrowserSupplier extends IOSupplier<Browser>, Accountable {} |
| } |