package org.apache.lucene.index;
/*
* 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.
*/
import java.io.IOException;
import org.apache.lucene.search.SearcherManager; // javadocs
import org.apache.lucene.util.Bits;
/** {@code AtomicReader} is an abstract class, providing an interface for accessing an
index. Search of an index is done entirely through this abstract interface,
so that any subclass which implements it is searchable. IndexReaders implemented
by this subclass do not consist of several sub-readers,
they are atomic. They support retrieval of stored fields, doc values, terms,
and postings.
<p>For efficiency, in this API documents are often referred to via
<i>document numbers</i>, non-negative integers which each name a unique
document in the index. These document numbers are ephemeral -- they may change
as documents are added to and deleted from an index. Clients should thus not
rely on a given document having the same number between sessions.
<p>
<a name="thread-safety"></a><p><b>NOTE</b>: {@link
IndexReader} instances are completely thread
safe, meaning multiple threads can call any of its methods,
concurrently. If your application requires external
synchronization, you should <b>not</b> synchronize on the
<code>IndexReader</code> instance; use your own
(non-Lucene) objects instead.
*/
public abstract class AtomicReader extends IndexReader {
private final AtomicReaderContext readerContext = new AtomicReaderContext(this);
/** Sole constructor. (For invocation by subclass
* constructors, typically implicit.) */
protected AtomicReader() {
super();
}
@Override
public final AtomicReaderContext getContext() {
ensureOpen();
return readerContext;
}
/**
* Returns true if there are norms stored for this field.
* @deprecated (4.0) use {@link #getFieldInfos()} and check {@link FieldInfo#hasNorms()}
* for the field instead.
*/
@Deprecated
public final boolean hasNorms(String field) throws IOException {
ensureOpen();
// note: using normValues(field) != null would potentially cause i/o
FieldInfo fi = getFieldInfos().fieldInfo(field);
return fi != null && fi.hasNorms();
}
/**
* Returns {@link Fields} for this reader.
* This method may return null if the reader has no
* postings.
*/
public abstract Fields fields() throws IOException;
@Override
public final int docFreq(Term term) throws IOException {
final Fields fields = fields();
if (fields == null) {
return 0;
}
final Terms terms = fields.terms(term.field());
if (terms == null) {
return 0;
}
final TermsEnum termsEnum = terms.iterator(null);
if (termsEnum.seekExact(term.bytes(), true)) {
return termsEnum.docFreq();
} else {
return 0;
}
}
/** Returns the number of documents containing the term
* <code>t</code>. This method returns 0 if the term or
* field does not exists. This method does not take into
* account deleted documents that have not yet been merged
* away. */
public final long totalTermFreq(Term term) throws IOException {
final Fields fields = fields();
if (fields == null) {
return 0;
}
final Terms terms = fields.terms(term.field());
if (terms == null) {
return 0;
}
final TermsEnum termsEnum = terms.iterator(null);
if (termsEnum.seekExact(term.bytes(), true)) {
return termsEnum.totalTermFreq();
} else {
return 0;
}
}
/** This may return null if the field does not exist.*/
public final Terms terms(String field) throws IOException {
final Fields fields = fields();
if (fields == null) {
return null;
}
return fields.terms(field);
}
/** Returns {@link DocsEnum} for the specified term.
* This will return null if either the field or
* term does not exist.
* @see TermsEnum#docs(Bits, DocsEnum) */
public final DocsEnum termDocsEnum(Term term) throws IOException {
assert term.field() != null;
assert term.bytes() != null;
final Fields fields = fields();
if (fields != null) {
final Terms terms = fields.terms(term.field());
if (terms != null) {
final TermsEnum termsEnum = terms.iterator(null);
if (termsEnum.seekExact(term.bytes(), true)) {
return termsEnum.docs(getLiveDocs(), null);
}
}
}
return null;
}
/** Returns {@link DocsAndPositionsEnum} for the specified
* term. This will return null if the
* field or term does not exist or positions weren't indexed.
* @see TermsEnum#docsAndPositions(Bits, DocsAndPositionsEnum) */
public final DocsAndPositionsEnum termPositionsEnum(Term term) throws IOException {
assert term.field() != null;
assert term.bytes() != null;
final Fields fields = fields();
if (fields != null) {
final Terms terms = fields.terms(term.field());
if (terms != null) {
final TermsEnum termsEnum = terms.iterator(null);
if (termsEnum.seekExact(term.bytes(), true)) {
return termsEnum.docsAndPositions(getLiveDocs(), null);
}
}
}
return null;
}
/**
* Returns {@link DocValues} for this field.
* This method may return null if the reader has no per-document
* values stored.
*/
public abstract DocValues docValues(String field) throws IOException;
/**
* Returns {@link DocValues} for this field's normalization values.
* This method may return null if the field has no norms.
*/
public abstract DocValues normValues(String field) throws IOException;
/**
* Get the {@link FieldInfos} describing all fields in
* this reader.
* @lucene.experimental
*/
public abstract FieldInfos getFieldInfos();
/** Returns the {@link Bits} representing live (not
* deleted) docs. A set bit indicates the doc ID has not
* been deleted. If this method returns null it means
* there are no deleted documents (all documents are
* live).
*
* The returned instance has been safely published for
* use by multiple threads without additional
* synchronization.
*/
public abstract Bits getLiveDocs();
}