/*
* 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.compressing;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.apache.lucene.codecs.CodecUtil;
import org.apache.lucene.codecs.StoredFieldsReader;
import org.apache.lucene.codecs.StoredFieldsWriter;
import org.apache.lucene.codecs.compressing.CompressingStoredFieldsReader.SerializedDocument;
import org.apache.lucene.index.CorruptIndexException;
import org.apache.lucene.index.DocIDMerger;
import org.apache.lucene.index.FieldInfo;
import org.apache.lucene.index.FieldInfos;
import org.apache.lucene.index.IndexFileNames;
import org.apache.lucene.index.IndexableField;
import org.apache.lucene.index.MergeState;
import org.apache.lucene.index.SegmentInfo;
import org.apache.lucene.store.DataOutput;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.GrowableByteArrayDataOutput;
import org.apache.lucene.store.IOContext;
import org.apache.lucene.store.IndexInput;
import org.apache.lucene.store.IndexOutput;
import org.apache.lucene.util.ArrayUtil;
import org.apache.lucene.util.BitUtil;
import org.apache.lucene.util.Bits;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.util.packed.PackedInts;
import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS;
/**
* {@link StoredFieldsWriter} impl for {@link CompressingStoredFieldsFormat}.
* @lucene.experimental
*/
public final class CompressingStoredFieldsWriter extends StoredFieldsWriter {
/** Extension of stored fields file */
public static final String FIELDS_EXTENSION = "fdt";
/** Extension of stored fields index file */
public static final String FIELDS_INDEX_EXTENSION = "fdx";
static final int STRING = 0x00;
static final int BYTE_ARR = 0x01;
static final int NUMERIC_INT = 0x02;
static final int NUMERIC_FLOAT = 0x03;
static final int NUMERIC_LONG = 0x04;
static final int NUMERIC_DOUBLE = 0x05;
static final int TYPE_BITS = PackedInts.bitsRequired(NUMERIC_DOUBLE);
static final int TYPE_MASK = (int) PackedInts.maxValue(TYPE_BITS);
static final String CODEC_SFX_IDX = "Index";
static final String CODEC_SFX_DAT = "Data";
static final int VERSION_START = 1;
static final int VERSION_CURRENT = VERSION_START;
private final String segment;
private CompressingStoredFieldsIndexWriter indexWriter;
private IndexOutput fieldsStream;
private Compressor compressor;
private final CompressionMode compressionMode;
private final int chunkSize;
private final int maxDocsPerChunk;
private final GrowableByteArrayDataOutput bufferedDocs;
private int[] numStoredFields; // number of stored fields
private int[] endOffsets; // end offsets in bufferedDocs
private int docBase; // doc ID at the beginning of the chunk
private int numBufferedDocs; // docBase + numBufferedDocs == current doc ID
private long numChunks; // number of compressed blocks written
private long numDirtyChunks; // number of incomplete compressed blocks written
/** Sole constructor. */
public CompressingStoredFieldsWriter(Directory directory, SegmentInfo si, String segmentSuffix, IOContext context,
String formatName, CompressionMode compressionMode, int chunkSize, int maxDocsPerChunk, int blockSize) throws IOException {
assert directory != null;
this.segment = si.name;
this.compressionMode = compressionMode;
this.compressor = compressionMode.newCompressor();
this.chunkSize = chunkSize;
this.maxDocsPerChunk = maxDocsPerChunk;
this.docBase = 0;
this.bufferedDocs = new GrowableByteArrayDataOutput(chunkSize);
this.numStoredFields = new int[16];
this.endOffsets = new int[16];
this.numBufferedDocs = 0;
boolean success = false;
IndexOutput indexStream = directory.createOutput(IndexFileNames.segmentFileName(segment, segmentSuffix, FIELDS_INDEX_EXTENSION),
context);
try {
fieldsStream = directory.createOutput(IndexFileNames.segmentFileName(segment, segmentSuffix, FIELDS_EXTENSION),
context);
final String codecNameIdx = formatName + CODEC_SFX_IDX;
final String codecNameDat = formatName + CODEC_SFX_DAT;
CodecUtil.writeIndexHeader(indexStream, codecNameIdx, VERSION_CURRENT, si.getId(), segmentSuffix);
CodecUtil.writeIndexHeader(fieldsStream, codecNameDat, VERSION_CURRENT, si.getId(), segmentSuffix);
assert CodecUtil.indexHeaderLength(codecNameDat, segmentSuffix) == fieldsStream.getFilePointer();
assert CodecUtil.indexHeaderLength(codecNameIdx, segmentSuffix) == indexStream.getFilePointer();
indexWriter = new CompressingStoredFieldsIndexWriter(indexStream, blockSize);
indexStream = null;
fieldsStream.writeVInt(chunkSize);
fieldsStream.writeVInt(PackedInts.VERSION_CURRENT);
success = true;
} finally {
if (!success) {
IOUtils.closeWhileHandlingException(fieldsStream, indexStream, indexWriter);
}
}
}
@Override
public void close() throws IOException {
try {
IOUtils.close(fieldsStream, indexWriter, compressor);
} finally {
fieldsStream = null;
indexWriter = null;
compressor = null;
}
}
private int numStoredFieldsInDoc;
@Override
public void startDocument() throws IOException {
}
@Override
public void finishDocument() throws IOException {
if (numBufferedDocs == this.numStoredFields.length) {
final int newLength = ArrayUtil.oversize(numBufferedDocs + 1, 4);
this.numStoredFields = Arrays.copyOf(this.numStoredFields, newLength);
endOffsets = Arrays.copyOf(endOffsets, newLength);
}
this.numStoredFields[numBufferedDocs] = numStoredFieldsInDoc;
numStoredFieldsInDoc = 0;
endOffsets[numBufferedDocs] = bufferedDocs.getPosition();
++numBufferedDocs;
if (triggerFlush()) {
flush();
}
}
private static void saveInts(int[] values, int length, DataOutput out) throws IOException {
assert length > 0;
if (length == 1) {
out.writeVInt(values[0]);
} else {
boolean allEqual = true;
for (int i = 1; i < length; ++i) {
if (values[i] != values[0]) {
allEqual = false;
break;
}
}
if (allEqual) {
out.writeVInt(0);
out.writeVInt(values[0]);
} else {
long max = 0;
for (int i = 0; i < length; ++i) {
max |= values[i];
}
final int bitsRequired = PackedInts.bitsRequired(max);
out.writeVInt(bitsRequired);
final PackedInts.Writer w = PackedInts.getWriterNoHeader(out, PackedInts.Format.PACKED, length, bitsRequired, 1);
for (int i = 0; i < length; ++i) {
w.add(values[i]);
}
w.finish();
}
}
}
private void writeHeader(int docBase, int numBufferedDocs, int[] numStoredFields, int[] lengths, boolean sliced) throws IOException {
final int slicedBit = sliced ? 1 : 0;
// save docBase and numBufferedDocs
fieldsStream.writeVInt(docBase);
fieldsStream.writeVInt((numBufferedDocs) << 1 | slicedBit);
// save numStoredFields
saveInts(numStoredFields, numBufferedDocs, fieldsStream);
// save lengths
saveInts(lengths, numBufferedDocs, fieldsStream);
}
private boolean triggerFlush() {
return bufferedDocs.getPosition() >= chunkSize || // chunks of at least chunkSize bytes
numBufferedDocs >= maxDocsPerChunk;
}
private void flush() throws IOException {
indexWriter.writeIndex(numBufferedDocs, fieldsStream.getFilePointer());
// transform end offsets into lengths
final int[] lengths = endOffsets;
for (int i = numBufferedDocs - 1; i > 0; --i) {
lengths[i] = endOffsets[i] - endOffsets[i - 1];
assert lengths[i] >= 0;
}
final boolean sliced = bufferedDocs.getPosition() >= 2 * chunkSize;
writeHeader(docBase, numBufferedDocs, numStoredFields, lengths, sliced);
// compress stored fields to fieldsStream
if (sliced) {
// big chunk, slice it
for (int compressed = 0; compressed < bufferedDocs.getPosition(); compressed += chunkSize) {
compressor.compress(bufferedDocs.getBytes(), compressed, Math.min(chunkSize, bufferedDocs.getPosition() - compressed), fieldsStream);
}
} else {
compressor.compress(bufferedDocs.getBytes(), 0, bufferedDocs.getPosition(), fieldsStream);
}
// reset
docBase += numBufferedDocs;
numBufferedDocs = 0;
bufferedDocs.reset();
numChunks++;
}
@Override
public void writeField(FieldInfo info, IndexableField field)
throws IOException {
++numStoredFieldsInDoc;
int bits = 0;
final BytesRef bytes;
final String string;
Number number = field.numericValue();
if (number != null) {
if (number instanceof Byte || number instanceof Short || number instanceof Integer) {
bits = NUMERIC_INT;
} else if (number instanceof Long) {
bits = NUMERIC_LONG;
} else if (number instanceof Float) {
bits = NUMERIC_FLOAT;
} else if (number instanceof Double) {
bits = NUMERIC_DOUBLE;
} else {
throw new IllegalArgumentException("cannot store numeric type " + number.getClass());
}
string = null;
bytes = null;
} else {
bytes = field.binaryValue();
if (bytes != null) {
bits = BYTE_ARR;
string = null;
} else {
bits = STRING;
string = field.stringValue();
if (string == null) {
throw new IllegalArgumentException("field " + field.name() + " is stored but does not have binaryValue, stringValue nor numericValue");
}
}
}
final long infoAndBits = (((long) info.number) << TYPE_BITS) | bits;
bufferedDocs.writeVLong(infoAndBits);
if (bytes != null) {
bufferedDocs.writeVInt(bytes.length);
bufferedDocs.writeBytes(bytes.bytes, bytes.offset, bytes.length);
} else if (string != null) {
bufferedDocs.writeString(string);
} else {
if (number instanceof Byte || number instanceof Short || number instanceof Integer) {
bufferedDocs.writeZInt(number.intValue());
} else if (number instanceof Long) {
writeTLong(bufferedDocs, number.longValue());
} else if (number instanceof Float) {
writeZFloat(bufferedDocs, number.floatValue());
} else if (number instanceof Double) {
writeZDouble(bufferedDocs, number.doubleValue());
} else {
throw new AssertionError("Cannot get here");
}
}
}
// -0 isn't compressed.
static final int NEGATIVE_ZERO_FLOAT = Float.floatToIntBits(-0f);
static final long NEGATIVE_ZERO_DOUBLE = Double.doubleToLongBits(-0d);
// for compression of timestamps
static final long SECOND = 1000L;
static final long HOUR = 60 * 60 * SECOND;
static final long DAY = 24 * HOUR;
static final int SECOND_ENCODING = 0x40;
static final int HOUR_ENCODING = 0x80;
static final int DAY_ENCODING = 0xC0;
/**
* Writes a float in a variable-length format. Writes between one and
* five bytes. Small integral values typically take fewer bytes.
* <p>
* ZFloat --> Header, Bytes*?
* <ul>
* <li>Header --> {@link DataOutput#writeByte Uint8}. When it is
* equal to 0xFF then the value is negative and stored in the next
* 4 bytes. Otherwise if the first bit is set then the other bits
* in the header encode the value plus one and no other
* bytes are read. Otherwise, the value is a positive float value
* whose first byte is the header, and 3 bytes need to be read to
* complete it.
* <li>Bytes --> Potential additional bytes to read depending on the
* header.
* </ul>
*/
static void writeZFloat(DataOutput out, float f) throws IOException {
int intVal = (int) f;
final int floatBits = Float.floatToIntBits(f);
if (f == intVal
&& intVal >= -1
&& intVal <= 0x7D
&& floatBits != NEGATIVE_ZERO_FLOAT) {
// small integer value [-1..125]: single byte
out.writeByte((byte) (0x80 | (1 + intVal)));
} else if ((floatBits >>> 31) == 0) {
// other positive floats: 4 bytes
out.writeInt(floatBits);
} else {
// other negative float: 5 bytes
out.writeByte((byte) 0xFF);
out.writeInt(floatBits);
}
}
/**
* Writes a float in a variable-length format. Writes between one and
* five bytes. Small integral values typically take fewer bytes.
* <p>
* ZFloat --> Header, Bytes*?
* <ul>
* <li>Header --> {@link DataOutput#writeByte Uint8}. When it is
* equal to 0xFF then the value is negative and stored in the next
* 8 bytes. When it is equal to 0xFE then the value is stored as a
* float in the next 4 bytes. Otherwise if the first bit is set
* then the other bits in the header encode the value plus one and
* no other bytes are read. Otherwise, the value is a positive float
* value whose first byte is the header, and 7 bytes need to be read
* to complete it.
* <li>Bytes --> Potential additional bytes to read depending on the
* header.
* </ul>
*/
static void writeZDouble(DataOutput out, double d) throws IOException {
int intVal = (int) d;
final long doubleBits = Double.doubleToLongBits(d);
if (d == intVal &&
intVal >= -1 &&
intVal <= 0x7C &&
doubleBits != NEGATIVE_ZERO_DOUBLE) {
// small integer value [-1..124]: single byte
out.writeByte((byte) (0x80 | (intVal + 1)));
return;
} else if (d == (float) d) {
// d has an accurate float representation: 5 bytes
out.writeByte((byte) 0xFE);
out.writeInt(Float.floatToIntBits((float) d));
} else if ((doubleBits >>> 63) == 0) {
// other positive doubles: 8 bytes
out.writeLong(doubleBits);
} else {
// other negative doubles: 9 bytes
out.writeByte((byte) 0xFF);
out.writeLong(doubleBits);
}
}
/**
* Writes a long in a variable-length format. Writes between one and
* ten bytes. Small values or values representing timestamps with day,
* hour or second precision typically require fewer bytes.
* <p>
* ZLong --> Header, Bytes*?
* <ul>
* <li>Header --> The first two bits indicate the compression scheme:
* <ul>
* <li>00 - uncompressed
* <li>01 - multiple of 1000 (second)
* <li>10 - multiple of 3600000 (hour)
* <li>11 - multiple of 86400000 (day)
* </ul>
* Then the next bit is a continuation bit, indicating whether more
* bytes need to be read, and the last 5 bits are the lower bits of
* the encoded value. In order to reconstruct the value, you need to
* combine the 5 lower bits of the header with a vLong in the next
* bytes (if the continuation bit is set to 1). Then
* {@link BitUtil#zigZagDecode(int) zigzag-decode} it and finally
* multiply by the multiple corresponding to the compression scheme.
* <li>Bytes --> Potential additional bytes to read depending on the
* header.
* </ul>
*/
// T for "timestamp"
static void writeTLong(DataOutput out, long l) throws IOException {
int header;
if (l % SECOND != 0) {
header = 0;
} else if (l % DAY == 0) {
// timestamp with day precision
header = DAY_ENCODING;
l /= DAY;
} else if (l % HOUR == 0) {
// timestamp with hour precision, or day precision with a timezone
header = HOUR_ENCODING;
l /= HOUR;
} else {
// timestamp with second precision
header = SECOND_ENCODING;
l /= SECOND;
}
final long zigZagL = BitUtil.zigZagEncode(l);
header |= (zigZagL & 0x1F); // last 5 bits
final long upperBits = zigZagL >>> 5;
if (upperBits != 0) {
header |= 0x20;
}
out.writeByte((byte) header);
if (upperBits != 0) {
out.writeVLong(upperBits);
}
}
@Override
public void finish(FieldInfos fis, int numDocs) throws IOException {
if (numBufferedDocs > 0) {
flush();
numDirtyChunks++; // incomplete: we had to force this flush
} else {
assert bufferedDocs.getPosition() == 0;
}
if (docBase != numDocs) {
throw new RuntimeException("Wrote " + docBase + " docs, finish called with numDocs=" + numDocs);
}
indexWriter.finish(numDocs, fieldsStream.getFilePointer());
fieldsStream.writeVLong(numChunks);
fieldsStream.writeVLong(numDirtyChunks);
CodecUtil.writeFooter(fieldsStream);
assert bufferedDocs.getPosition() == 0;
}
// bulk merge is scary: its caused corruption bugs in the past.
// we try to be extra safe with this impl, but add an escape hatch to
// have a workaround for undiscovered bugs.
static final String BULK_MERGE_ENABLED_SYSPROP = CompressingStoredFieldsWriter.class.getName() + ".enableBulkMerge";
static final boolean BULK_MERGE_ENABLED;
static {
boolean v = true;
try {
v = Boolean.parseBoolean(System.getProperty(BULK_MERGE_ENABLED_SYSPROP, "true"));
} catch (SecurityException ignored) {}
BULK_MERGE_ENABLED = v;
}
@Override
public int merge(MergeState mergeState) throws IOException {
int docCount = 0;
int numReaders = mergeState.maxDocs.length;
MatchingReaders matching = new MatchingReaders(mergeState);
if (mergeState.needsIndexSort) {
/**
* If all readers are compressed and they have the same fieldinfos then we can merge the serialized document
* directly.
*/
List<CompressingStoredFieldsMergeSub> subs = new ArrayList<>();
for(int i=0;i<mergeState.storedFieldsReaders.length;i++) {
if (matching.matchingReaders[i] &&
mergeState.storedFieldsReaders[i] instanceof CompressingStoredFieldsReader) {
CompressingStoredFieldsReader storedFieldsReader = (CompressingStoredFieldsReader) mergeState.storedFieldsReaders[i];
storedFieldsReader.checkIntegrity();
subs.add(new CompressingStoredFieldsMergeSub(storedFieldsReader, mergeState.docMaps[i], mergeState.maxDocs[i]));
} else {
return super.merge(mergeState);
}
}
final DocIDMerger<CompressingStoredFieldsMergeSub> docIDMerger =
DocIDMerger.of(subs, true);
while (true) {
CompressingStoredFieldsMergeSub sub = docIDMerger.next();
if (sub == null) {
break;
}
assert sub.mappedDocID == docCount;
SerializedDocument doc = sub.reader.document(sub.docID);
startDocument();
bufferedDocs.copyBytes(doc.in, doc.length);
numStoredFieldsInDoc = doc.numStoredFields;
finishDocument();
++docCount;
}
finish(mergeState.mergeFieldInfos, docCount);
return docCount;
}
for (int readerIndex=0;readerIndex<numReaders;readerIndex++) {
MergeVisitor visitor = new MergeVisitor(mergeState, readerIndex);
CompressingStoredFieldsReader matchingFieldsReader = null;
if (matching.matchingReaders[readerIndex]) {
final StoredFieldsReader fieldsReader = mergeState.storedFieldsReaders[readerIndex];
// we can only bulk-copy if the matching reader is also a CompressingStoredFieldsReader
if (fieldsReader != null && fieldsReader instanceof CompressingStoredFieldsReader) {
matchingFieldsReader = (CompressingStoredFieldsReader) fieldsReader;
}
}
final int maxDoc = mergeState.maxDocs[readerIndex];
final Bits liveDocs = mergeState.liveDocs[readerIndex];
// if its some other format, or an older version of this format, or safety switch:
if (matchingFieldsReader == null || matchingFieldsReader.getVersion() != VERSION_CURRENT || BULK_MERGE_ENABLED == false) {
// naive merge...
StoredFieldsReader storedFieldsReader = mergeState.storedFieldsReaders[readerIndex];
if (storedFieldsReader != null) {
storedFieldsReader.checkIntegrity();
}
for (int docID = 0; docID < maxDoc; docID++) {
if (liveDocs != null && liveDocs.get(docID) == false) {
continue;
}
startDocument();
storedFieldsReader.visitDocument(docID, visitor);
finishDocument();
++docCount;
}
} else if (matchingFieldsReader.getCompressionMode() == compressionMode &&
matchingFieldsReader.getChunkSize() == chunkSize &&
matchingFieldsReader.getPackedIntsVersion() == PackedInts.VERSION_CURRENT &&
liveDocs == null &&
!tooDirty(matchingFieldsReader)) {
// optimized merge, raw byte copy
// its not worth fine-graining this if there are deletions.
// if the format is older, its always handled by the naive merge case above
assert matchingFieldsReader.getVersion() == VERSION_CURRENT;
matchingFieldsReader.checkIntegrity();
// flush any pending chunks
if (numBufferedDocs > 0) {
flush();
numDirtyChunks++; // incomplete: we had to force this flush
}
// iterate over each chunk. we use the stored fields index to find chunk boundaries,
// read the docstart + doccount from the chunk header (we write a new header, since doc numbers will change),
// and just copy the bytes directly.
IndexInput rawDocs = matchingFieldsReader.getFieldsStream();
CompressingStoredFieldsIndexReader index = matchingFieldsReader.getIndexReader();
rawDocs.seek(index.getStartPointer(0));
int docID = 0;
while (docID < maxDoc) {
// read header
int base = rawDocs.readVInt();
if (base != docID) {
throw new CorruptIndexException("invalid state: base=" + base + ", docID=" + docID, rawDocs);
}
int code = rawDocs.readVInt();
// write a new index entry and new header for this chunk.
int bufferedDocs = code >>> 1;
indexWriter.writeIndex(bufferedDocs, fieldsStream.getFilePointer());
fieldsStream.writeVInt(docBase); // rebase
fieldsStream.writeVInt(code);
docID += bufferedDocs;
docBase += bufferedDocs;
docCount += bufferedDocs;
if (docID > maxDoc) {
throw new CorruptIndexException("invalid state: base=" + base + ", count=" + bufferedDocs + ", maxDoc=" + maxDoc, rawDocs);
}
// copy bytes until the next chunk boundary (or end of chunk data).
// using the stored fields index for this isn't the most efficient, but fast enough
// and is a source of redundancy for detecting bad things.
final long end;
if (docID == maxDoc) {
end = matchingFieldsReader.getMaxPointer();
} else {
end = index.getStartPointer(docID);
}
fieldsStream.copyBytes(rawDocs, end - rawDocs.getFilePointer());
}
if (rawDocs.getFilePointer() != matchingFieldsReader.getMaxPointer()) {
throw new CorruptIndexException("invalid state: pos=" + rawDocs.getFilePointer() + ", max=" + matchingFieldsReader.getMaxPointer(), rawDocs);
}
// since we bulk merged all chunks, we inherit any dirty ones from this segment.
numChunks += matchingFieldsReader.getNumChunks();
numDirtyChunks += matchingFieldsReader.getNumDirtyChunks();
} else {
// optimized merge, we copy serialized (but decompressed) bytes directly
// even on simple docs (1 stored field), it seems to help by about 20%
// if the format is older, its always handled by the naive merge case above
assert matchingFieldsReader.getVersion() == VERSION_CURRENT;
matchingFieldsReader.checkIntegrity();
for (int docID = 0; docID < maxDoc; docID++) {
if (liveDocs != null && liveDocs.get(docID) == false) {
continue;
}
SerializedDocument doc = matchingFieldsReader.document(docID);
startDocument();
bufferedDocs.copyBytes(doc.in, doc.length);
numStoredFieldsInDoc = doc.numStoredFields;
finishDocument();
++docCount;
}
}
}
finish(mergeState.mergeFieldInfos, docCount);
return docCount;
}
/**
* Returns true if we should recompress this reader, even though we could bulk merge compressed data
* <p>
* The last chunk written for a segment is typically incomplete, so without recompressing,
* in some worst-case situations (e.g. frequent reopen with tiny flushes), over time the
* compression ratio can degrade. This is a safety switch.
*/
boolean tooDirty(CompressingStoredFieldsReader candidate) {
// more than 1% dirty, or more than hard limit of 1024 dirty chunks
return candidate.getNumDirtyChunks() > 1024 ||
candidate.getNumDirtyChunks() * 100 > candidate.getNumChunks();
}
private static class CompressingStoredFieldsMergeSub extends DocIDMerger.Sub {
private final CompressingStoredFieldsReader reader;
private final int maxDoc;
int docID = -1;
public CompressingStoredFieldsMergeSub(CompressingStoredFieldsReader reader, MergeState.DocMap docMap, int maxDoc) {
super(docMap);
this.maxDoc = maxDoc;
this.reader = reader;
}
@Override
public int nextDoc() {
docID++;
if (docID == maxDoc) {
return NO_MORE_DOCS;
} else {
return docID;
}
}
}
}