package org.apache.lucene.codecs.perfield;
/*
* 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 java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.ServiceLoader; // javadocs
import java.util.Set;
import java.util.TreeMap;
import java.util.TreeSet;
import org.apache.lucene.codecs.FieldsConsumer;
import org.apache.lucene.codecs.FieldsProducer;
import org.apache.lucene.codecs.PostingsFormat;
import org.apache.lucene.index.FieldInfo;
import org.apache.lucene.index.Fields;
import org.apache.lucene.index.SegmentReadState;
import org.apache.lucene.index.SegmentWriteState;
import org.apache.lucene.index.Terms;
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.util.RamUsageEstimator;
import static org.apache.lucene.index.FilterAtomicReader.FilterFields;
/**
* Enables per field postings support.
* <p>
* Note, when extending this class, the name ({@link #getName}) is
* written into the index. In order for the field to be read, the
* name must resolve to your implementation via {@link #forName(String)}.
* This method uses Java's
* {@link ServiceLoader Service Provider Interface} to resolve format names.
* <p>
* Files written by each posting format have an additional suffix containing the
* format name. For example, in a per-field configuration instead of <tt>_1.prx</tt>
* filenames would look like <tt>_1_Lucene40_0.prx</tt>.
* @see ServiceLoader
* @lucene.experimental
*/
public abstract class PerFieldPostingsFormat extends PostingsFormat {
/** Name of this {@link PostingsFormat}. */
public static final String PER_FIELD_NAME = "PerField40";
/** {@link FieldInfo} attribute name used to store the
* format name for each field. */
public static final String PER_FIELD_FORMAT_KEY = PerFieldPostingsFormat.class.getSimpleName() + ".format";
/** {@link FieldInfo} attribute name used to store the
* segment suffix name for each field. */
public static final String PER_FIELD_SUFFIX_KEY = PerFieldPostingsFormat.class.getSimpleName() + ".suffix";
/** Sole constructor. */
public PerFieldPostingsFormat() {
super(PER_FIELD_NAME);
}
/** Group of fields written by one PostingsFormat */
static class FieldsGroup {
final Set<String> fields = new TreeSet<>();
int suffix;
/** Custom SegmentWriteState for this group of fields,
* with the segmentSuffix uniqueified for this
* PostingsFormat */
SegmentWriteState state;
};
static String getSuffix(String formatName, String suffix) {
return formatName + "_" + suffix;
}
static String getFullSegmentSuffix(String fieldName, String outerSegmentSuffix, String segmentSuffix) {
if (outerSegmentSuffix.length() == 0) {
return segmentSuffix;
} else {
// TODO: support embedding; I think it should work but
// we need a test confirm to confirm
// return outerSegmentSuffix + "_" + segmentSuffix;
throw new IllegalStateException("cannot embed PerFieldPostingsFormat inside itself (field \"" + fieldName + "\" returned PerFieldPostingsFormat)");
}
}
private class FieldsWriter extends FieldsConsumer {
final SegmentWriteState writeState;
public FieldsWriter(SegmentWriteState writeState) {
this.writeState = writeState;
}
@Override
public void write(Fields fields) throws IOException {
// Maps a PostingsFormat instance to the suffix it
// should use
Map<PostingsFormat,FieldsGroup> formatToGroups = new HashMap<>();
// Holds last suffix of each PostingFormat name
Map<String,Integer> suffixes = new HashMap<>();
// First pass: assign field -> PostingsFormat
for(String field : fields) {
FieldInfo fieldInfo = writeState.fieldInfos.fieldInfo(field);
final PostingsFormat format = getPostingsFormatForField(field);
if (format == null) {
throw new IllegalStateException("invalid null PostingsFormat for field=\"" + field + "\"");
}
String formatName = format.getName();
FieldsGroup group = formatToGroups.get(format);
if (group == null) {
// First time we are seeing this format; create a
// new instance
// bump the suffix
Integer suffix = suffixes.get(formatName);
if (suffix == null) {
suffix = 0;
} else {
suffix = suffix + 1;
}
suffixes.put(formatName, suffix);
String segmentSuffix = getFullSegmentSuffix(field,
writeState.segmentSuffix,
getSuffix(formatName, Integer.toString(suffix)));
group = new FieldsGroup();
group.state = new SegmentWriteState(writeState, segmentSuffix);
group.suffix = suffix;
formatToGroups.put(format, group);
} else {
// we've already seen this format, so just grab its suffix
assert suffixes.containsKey(formatName);
}
group.fields.add(field);
String previousValue = fieldInfo.putAttribute(PER_FIELD_FORMAT_KEY, formatName);
assert previousValue == null;
previousValue = fieldInfo.putAttribute(PER_FIELD_SUFFIX_KEY, Integer.toString(group.suffix));
assert previousValue == null;
}
// Second pass: write postings
for(Map.Entry<PostingsFormat,FieldsGroup> ent : formatToGroups.entrySet()) {
PostingsFormat format = ent.getKey();
final FieldsGroup group = ent.getValue();
// Exposes only the fields from this group:
Fields maskedFields = new FilterFields(fields) {
@Override
public Iterator<String> iterator() {
return group.fields.iterator();
}
};
format.fieldsConsumer(group.state).write(maskedFields);
}
}
}
private class FieldsReader extends FieldsProducer {
private final Map<String,FieldsProducer> fields = new TreeMap<>();
private final Map<String,FieldsProducer> formats = new HashMap<>();
public FieldsReader(final SegmentReadState readState) throws IOException {
// Read _X.per and init each format:
boolean success = false;
try {
// Read field name -> format name
for (FieldInfo fi : readState.fieldInfos) {
if (fi.isIndexed()) {
final String fieldName = fi.name;
final String formatName = fi.getAttribute(PER_FIELD_FORMAT_KEY);
if (formatName != null) {
// null formatName means the field is in fieldInfos, but has no postings!
final String suffix = fi.getAttribute(PER_FIELD_SUFFIX_KEY);
assert suffix != null;
PostingsFormat format = PostingsFormat.forName(formatName);
String segmentSuffix = getSuffix(formatName, suffix);
if (!formats.containsKey(segmentSuffix)) {
formats.put(segmentSuffix, format.fieldsProducer(new SegmentReadState(readState, segmentSuffix)));
}
fields.put(fieldName, formats.get(segmentSuffix));
}
}
}
success = true;
} finally {
if (!success) {
IOUtils.closeWhileHandlingException(formats.values());
}
}
}
@Override
public Iterator<String> iterator() {
return Collections.unmodifiableSet(fields.keySet()).iterator();
}
@Override
public Terms terms(String field) throws IOException {
FieldsProducer fieldsProducer = fields.get(field);
return fieldsProducer == null ? null : fieldsProducer.terms(field);
}
@Override
public int size() {
return fields.size();
}
@Override
public void close() throws IOException {
IOUtils.close(formats.values());
}
@Override
public long ramBytesUsed() {
long sizeInBytes = 0;
for(Map.Entry<String,FieldsProducer> entry: formats.entrySet()) {
sizeInBytes += entry.getKey().length() * RamUsageEstimator.NUM_BYTES_CHAR;
sizeInBytes += entry.getValue().ramBytesUsed();
}
return sizeInBytes;
}
}
@Override
public final FieldsConsumer fieldsConsumer(SegmentWriteState state)
throws IOException {
return new FieldsWriter(state);
}
@Override
public final FieldsProducer fieldsProducer(SegmentReadState state)
throws IOException {
return new FieldsReader(state);
}
/**
* Returns the postings format that should be used for writing
* new segments of <code>field</code>.
* <p>
* The field to format mapping is written to the index, so
* this method is only invoked when writing, not when reading. */
public abstract PostingsFormat getPostingsFormatForField(String field);
}