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/*
* 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.facet.taxonomy;
import java.io.Closeable;
import java.io.IOException;
import java.util.Map;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.TwoPhaseCommit;
/**
* TaxonomyWriter is the interface which the faceted-search library uses to dynamically build the
* taxonomy at indexing time.
*
* Notes about concurrent access to the taxonomy:
*
*
An implementation must allow multiple readers and a single writer to be active concurrently.
* Readers follow so-called "point in time" semantics, i.e., a reader object will only see taxonomy
* entries which were available at the time it was created. What the writer writes is only available
* to (new) readers after the writer's commit() is called.
*
*
Faceted search keeps two indices - namely Lucene's main index, and this taxonomy index. When
* one or more readers are active concurrently with the writer, care must be taken to avoid an
* inconsistency between the state of these two indices: When writing to the indices, the taxonomy
* must always be committed to disk *before* the main index, because the main index refers to
* categories listed in the taxonomy. Such control can best be achieved by turning off the main
* index's "autocommit" feature, and explicitly calling commit() for both indices (first for the
* taxonomy, then for the main index). In old versions of Lucene (2.2 or earlier), when autocommit
* could not be turned off, a more complicated solution needs to be used. E.g., use some sort of
* (possibly inter-process) locking to ensure that a reader is being opened only right after both
* indices have been flushed (and before anything else is written to them).
*
* @lucene.experimental
*/
public interface TaxonomyWriter extends Closeable, TwoPhaseCommit {
/**
* addCategory() adds a category with a given path name to the taxonomy, and returns its ordinal.
* If the category was already present in the taxonomy, its existing ordinal is returned.
*
*
Before adding a category, addCategory() makes sure that all its ancestor categories exist in
* the taxonomy as well. As result, the ordinal of a category is guaranteed to be smaller then the
* ordinal of any of its descendants.
*/
public int addCategory(FacetLabel categoryPath) throws IOException;
/**
* getParent() returns the ordinal of the parent category of the category with the given ordinal.
*
*
When a category is specified as a path name, finding the path of its parent is as trivial as
* dropping the last component of the path. getParent() is functionally equivalent to calling
* getPath() on the given ordinal, dropping the last component of the path, and then calling
* getOrdinal() to get an ordinal back.
*
*
If the given ordinal is the ROOT_ORDINAL, an INVALID_ORDINAL is returned. If the given
* ordinal is a top-level category, the ROOT_ORDINAL is returned. If an invalid ordinal is given
* (negative or beyond the last available ordinal), an IndexOutOfBoundsException is thrown.
* However, it is expected that getParent will only be called for ordinals which are already known
* to be in the taxonomy. TODO (Facet): instead of a getParent(ordinal) method, consider having a
*
*
getCategory(categorypath, prefixlen) which is similar to addCategory except it doesn't add
* new categories; This method can be used to get the ordinals of all prefixes of the given
* category, and it can use exactly the same code and cache used by addCategory() so it means less
* code.
*/
public int getParent(int ordinal) throws IOException;
/**
* getSize() returns the number of categories in the taxonomy.
*
*
Because categories are numbered consecutively starting with 0, it means the taxonomy
* contains ordinals 0 through getSize()-1.
*
*
Note that the number returned by getSize() is often slightly higher than the number of
* categories inserted into the taxonomy; This is because when a category is added to the
* taxonomy, its ancestors are also added automatically (including the root, which always get
* ordinal 0).
*/
public int getSize();
/** Sets the commit user data iterable. See {@link IndexWriter#setLiveCommitData}. */
public void setLiveCommitData(Iterable> commitUserData);
/** Returns the commit user data iterable that was set on {@link #setLiveCommitData(Iterable)}. */
public Iterable> getLiveCommitData();
}