lindong28 commented on code in PR #97:
URL: https://github.com/apache/flink-ml/pull/97#discussion_r889952819
##########
flink-ml-iteration/src/main/java/org/apache/flink/iteration/datacache/nonkeyed/Segment.java:
##########
@@ -18,38 +18,80 @@
package org.apache.flink.iteration.datacache.nonkeyed;
+import org.apache.flink.annotation.Internal;
import org.apache.flink.core.fs.Path;
+import org.apache.flink.core.memory.MemorySegment;
-import java.io.Serializable;
+import java.util.List;
import java.util.Objects;
-/** A segment represents a single file for the cache. */
-public class Segment implements Serializable {
+import static org.apache.flink.util.Preconditions.checkArgument;
+import static org.apache.flink.util.Preconditions.checkNotNull;
+import static org.apache.flink.util.Preconditions.checkState;
+/** A segment contains the information about a cache unit. */
+@Internal
+public class Segment {
+
+ /** The path to the file containing cached records. */
private final Path path;
- /** The count of the records in the file. */
+ /** The count of the records in the segment. */
private final int count;
- /** The total length of file. */
- private final long size;
+ /** The total length of file containing cached records. */
+ private long fsSize = -1L;
+
+ /** The memory segments containing cached records. */
+ private List<MemorySegment> cache;
+
+ Segment(Path path, int count, long fsSize) {
+ this.path = checkNotNull(path);
+ checkArgument(count > 0);
+ this.count = count;
+ checkArgument(fsSize > 0);
+ this.fsSize = fsSize;
+ }
- public Segment(Path path, int count, long size) {
- this.path = path;
+ Segment(Path path, int count, List<MemorySegment> cache) {
+ this.path = checkNotNull(path);
+ checkArgument(count > 0);
this.count = count;
- this.size = size;
+ this.cache = checkNotNull(cache);
+ }
+
+ void setCache(List<MemorySegment> cache) {
+ this.cache = checkNotNull(cache);
}
- public Path getPath() {
+ void setDiskInfo(long fsSize) {
Review Comment:
Would it be more intuitive to rename this method as `setFsSize()`?
##########
flink-ml-iteration/src/main/java/org/apache/flink/iteration/datacache/nonkeyed/MemorySegmentWriter.java:
##########
@@ -0,0 +1,191 @@
+/*
+ * 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.flink.iteration.datacache.nonkeyed;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.core.memory.DataOutputView;
+import org.apache.flink.core.memory.DataOutputViewStreamWrapper;
+import org.apache.flink.core.memory.MemorySegment;
+import org.apache.flink.runtime.memory.MemoryAllocationException;
+import org.apache.flink.table.runtime.util.MemorySegmentPool;
+import org.apache.flink.util.Preconditions;
+
+import javax.annotation.Nullable;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+/** A class that writes cache data to memory segments. */
+@Internal
+class MemorySegmentWriter<T> implements SegmentWriter<T> {
+
+ /** The tool to serialize received records into bytes. */
+ private final TypeSerializer<T> serializer;
+
+ /** The pre-allocated path to hold cached records into file system. */
+ private final Path path;
+
+ /** The pool to allocate memory segments from. */
+ private final MemorySegmentPool segmentPool;
+
+ /** The output stream to write serialized content to memory segments. */
+ private final ManagedMemoryOutputStream outputStream;
+
+ /** The wrapper view of output stream to be used with TypeSerializer API.
*/
+ private final DataOutputView outputView;
+
+ /** The number of records added so far. */
+ private int count;
+
+ MemorySegmentWriter(
+ TypeSerializer<T> serializer,
+ Path path,
+ MemorySegmentPool segmentPool,
+ long expectedSize)
+ throws MemoryAllocationException {
+ this.serializer = serializer;
+ this.path = path;
+ this.segmentPool = segmentPool;
+ this.outputStream = new ManagedMemoryOutputStream(segmentPool,
expectedSize);
+ this.outputView = new DataOutputViewStreamWrapper(outputStream);
+ this.count = 0;
+ }
+
+ @Override
+ public boolean addRecord(T record) throws IOException {
+ if (outputStream.getPos() >= DataCacheWriter.MAX_SEGMENT_SIZE) {
+ return false;
+ }
+ try {
+ serializer.serialize(record, outputView);
+ count++;
+ return true;
+ } catch (IOException e) {
+ if (e.getCause() instanceof MemoryAllocationException) {
+ return false;
+ }
+ throw e;
+ }
+ }
+
+ @Override
+ public Optional<Segment> finish() throws IOException {
+ if (count > 0) {
+ return Optional.of(new Segment(path, count,
outputStream.getSegments()));
+ } else {
+ segmentPool.returnAll(outputStream.getSegments());
+ return Optional.empty();
+ }
+ }
+
+ /** An output stream subclass that accepts bytes and writes them to memory
segments. */
+ private static class ManagedMemoryOutputStream extends OutputStream {
+
+ /** The pool to allocate memory segments from. */
+ private final MemorySegmentPool segmentPool;
+
+ /** The number of bytes in a memory segment. */
+ private final int pageSize;
+
+ /** The memory segments containing written bytes. */
+ private final List<MemorySegment> segments = new ArrayList<>();
+
+ /** The index of the segment that currently accepts written bytes. */
+ private int segmentIndex;
+
+ /** THe number of bytes in the current segment that have been written.
*/
+ private int segmentOffset;
+
+ /** THe number of bytes that have been written so far. */
+ private long globalOffset;
+
+ public ManagedMemoryOutputStream(MemorySegmentPool segmentPool, long
expectedSize)
+ throws MemoryAllocationException {
+ this.segmentPool = segmentPool;
+ this.pageSize = segmentPool.pageSize();
+ this.segmentIndex = 0;
+ this.segmentOffset = 0;
+
+ Preconditions.checkArgument(expectedSize >= 0);
+ ensureCapacity(Math.max(expectedSize, 1L));
+ }
+
+ public long getPos() {
+ return globalOffset;
+ }
+
+ public List<MemorySegment> getSegments() {
+ return segments;
+ }
+
+ @Override
+ public void write(int b) throws IOException {
+ write(new byte[] {(byte) b}, 0, 1);
+ }
+
+ @Override
+ public void write(@Nullable byte[] b, int off, int len) throws
IOException {
+ try {
+ ensureCapacity(globalOffset + len);
+ } catch (MemoryAllocationException e) {
+ throw new IOException(e);
+ }
+ writeRecursive(b, off, len);
+ }
+
+ private void ensureCapacity(long capacity) throws
MemoryAllocationException {
+ Preconditions.checkArgument(capacity > 0);
+ int required =
+ (int) (capacity % pageSize == 0 ? capacity / pageSize :
capacity / pageSize + 1)
+ - segments.size();
+
+ List<MemorySegment> allocatedSegments = new ArrayList<>();
+ for (int i = 0; i < required; i++) {
+ MemorySegment memorySegment = segmentPool.nextSegment();
+ if (memorySegment == null) {
+ segmentPool.returnAll(allocatedSegments);
+ throw new MemoryAllocationException();
+ }
+ allocatedSegments.add(memorySegment);
+ }
+
+ segments.addAll(allocatedSegments);
+ }
+
+ private void writeRecursive(byte[] b, int off, int len) {
Review Comment:
Could we change this function to be iterative to improve performance?
##########
flink-ml-iteration/src/main/java/org/apache/flink/iteration/datacache/nonkeyed/MemorySegmentWriter.java:
##########
@@ -0,0 +1,191 @@
+/*
+ * 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.flink.iteration.datacache.nonkeyed;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.core.memory.DataOutputView;
+import org.apache.flink.core.memory.DataOutputViewStreamWrapper;
+import org.apache.flink.core.memory.MemorySegment;
+import org.apache.flink.runtime.memory.MemoryAllocationException;
+import org.apache.flink.table.runtime.util.MemorySegmentPool;
+import org.apache.flink.util.Preconditions;
+
+import javax.annotation.Nullable;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+/** A class that writes cache data to memory segments. */
+@Internal
+class MemorySegmentWriter<T> implements SegmentWriter<T> {
+
+ /** The tool to serialize received records into bytes. */
+ private final TypeSerializer<T> serializer;
+
+ /** The pre-allocated path to hold cached records into file system. */
+ private final Path path;
+
+ /** The pool to allocate memory segments from. */
+ private final MemorySegmentPool segmentPool;
+
+ /** The output stream to write serialized content to memory segments. */
+ private final ManagedMemoryOutputStream outputStream;
+
+ /** The wrapper view of output stream to be used with TypeSerializer API.
*/
+ private final DataOutputView outputView;
+
+ /** The number of records added so far. */
+ private int count;
+
+ MemorySegmentWriter(
+ TypeSerializer<T> serializer,
+ Path path,
+ MemorySegmentPool segmentPool,
+ long expectedSize)
+ throws MemoryAllocationException {
+ this.serializer = serializer;
+ this.path = path;
+ this.segmentPool = segmentPool;
+ this.outputStream = new ManagedMemoryOutputStream(segmentPool,
expectedSize);
+ this.outputView = new DataOutputViewStreamWrapper(outputStream);
+ this.count = 0;
+ }
+
+ @Override
+ public boolean addRecord(T record) throws IOException {
+ if (outputStream.getPos() >= DataCacheWriter.MAX_SEGMENT_SIZE) {
+ return false;
+ }
+ try {
+ serializer.serialize(record, outputView);
+ count++;
+ return true;
+ } catch (IOException e) {
+ if (e.getCause() instanceof MemoryAllocationException) {
+ return false;
+ }
+ throw e;
+ }
+ }
+
+ @Override
+ public Optional<Segment> finish() throws IOException {
+ if (count > 0) {
+ return Optional.of(new Segment(path, count,
outputStream.getSegments()));
+ } else {
+ segmentPool.returnAll(outputStream.getSegments());
+ return Optional.empty();
+ }
+ }
+
+ /** An output stream subclass that accepts bytes and writes them to memory
segments. */
+ private static class ManagedMemoryOutputStream extends OutputStream {
+
+ /** The pool to allocate memory segments from. */
+ private final MemorySegmentPool segmentPool;
+
+ /** The number of bytes in a memory segment. */
+ private final int pageSize;
+
+ /** The memory segments containing written bytes. */
+ private final List<MemorySegment> segments = new ArrayList<>();
+
+ /** The index of the segment that currently accepts written bytes. */
+ private int segmentIndex;
+
+ /** THe number of bytes in the current segment that have been written.
*/
+ private int segmentOffset;
+
+ /** THe number of bytes that have been written so far. */
+ private long globalOffset;
+
+ public ManagedMemoryOutputStream(MemorySegmentPool segmentPool, long
expectedSize)
+ throws MemoryAllocationException {
+ this.segmentPool = segmentPool;
+ this.pageSize = segmentPool.pageSize();
+ this.segmentIndex = 0;
+ this.segmentOffset = 0;
+
+ Preconditions.checkArgument(expectedSize >= 0);
+ ensureCapacity(Math.max(expectedSize, 1L));
+ }
+
+ public long getPos() {
+ return globalOffset;
+ }
+
+ public List<MemorySegment> getSegments() {
+ return segments;
+ }
+
+ @Override
+ public void write(int b) throws IOException {
+ write(new byte[] {(byte) b}, 0, 1);
+ }
+
+ @Override
+ public void write(@Nullable byte[] b, int off, int len) throws
IOException {
+ try {
+ ensureCapacity(globalOffset + len);
+ } catch (MemoryAllocationException e) {
+ throw new IOException(e);
+ }
+ writeRecursive(b, off, len);
+ }
+
+ private void ensureCapacity(long capacity) throws
MemoryAllocationException {
+ Preconditions.checkArgument(capacity > 0);
+ int required =
+ (int) (capacity % pageSize == 0 ? capacity / pageSize :
capacity / pageSize + 1)
+ - segments.size();
+
+ List<MemorySegment> allocatedSegments = new ArrayList<>();
+ for (int i = 0; i < required; i++) {
+ MemorySegment memorySegment = segmentPool.nextSegment();
+ if (memorySegment == null) {
+ segmentPool.returnAll(allocatedSegments);
Review Comment:
Should we also return `segments` to the segmentPool? This could be useful
when `write(...)` encounters limit.
##########
flink-ml-iteration/src/main/java/org/apache/flink/iteration/datacache/nonkeyed/MemorySegmentWriter.java:
##########
@@ -0,0 +1,191 @@
+/*
+ * 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.flink.iteration.datacache.nonkeyed;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.core.memory.DataOutputView;
+import org.apache.flink.core.memory.DataOutputViewStreamWrapper;
+import org.apache.flink.core.memory.MemorySegment;
+import org.apache.flink.runtime.memory.MemoryAllocationException;
+import org.apache.flink.table.runtime.util.MemorySegmentPool;
+import org.apache.flink.util.Preconditions;
+
+import javax.annotation.Nullable;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+/** A class that writes cache data to memory segments. */
+@Internal
+class MemorySegmentWriter<T> implements SegmentWriter<T> {
+
+ /** The tool to serialize received records into bytes. */
+ private final TypeSerializer<T> serializer;
+
+ /** The pre-allocated path to hold cached records into file system. */
+ private final Path path;
+
+ /** The pool to allocate memory segments from. */
+ private final MemorySegmentPool segmentPool;
+
+ /** The output stream to write serialized content to memory segments. */
+ private final ManagedMemoryOutputStream outputStream;
+
+ /** The wrapper view of output stream to be used with TypeSerializer API.
*/
+ private final DataOutputView outputView;
+
+ /** The number of records added so far. */
+ private int count;
+
+ MemorySegmentWriter(
+ TypeSerializer<T> serializer,
+ Path path,
+ MemorySegmentPool segmentPool,
+ long expectedSize)
+ throws MemoryAllocationException {
+ this.serializer = serializer;
+ this.path = path;
+ this.segmentPool = segmentPool;
+ this.outputStream = new ManagedMemoryOutputStream(segmentPool,
expectedSize);
+ this.outputView = new DataOutputViewStreamWrapper(outputStream);
+ this.count = 0;
+ }
+
+ @Override
+ public boolean addRecord(T record) throws IOException {
+ if (outputStream.getPos() >= DataCacheWriter.MAX_SEGMENT_SIZE) {
+ return false;
+ }
+ try {
+ serializer.serialize(record, outputView);
+ count++;
+ return true;
+ } catch (IOException e) {
+ if (e.getCause() instanceof MemoryAllocationException) {
+ return false;
+ }
+ throw e;
+ }
+ }
+
+ @Override
+ public Optional<Segment> finish() throws IOException {
+ if (count > 0) {
+ return Optional.of(new Segment(path, count,
outputStream.getSegments()));
+ } else {
+ segmentPool.returnAll(outputStream.getSegments());
+ return Optional.empty();
+ }
+ }
+
+ /** An output stream subclass that accepts bytes and writes them to memory
segments. */
+ private static class ManagedMemoryOutputStream extends OutputStream {
+
+ /** The pool to allocate memory segments from. */
+ private final MemorySegmentPool segmentPool;
+
+ /** The number of bytes in a memory segment. */
+ private final int pageSize;
+
+ /** The memory segments containing written bytes. */
+ private final List<MemorySegment> segments = new ArrayList<>();
+
+ /** The index of the segment that currently accepts written bytes. */
+ private int segmentIndex;
+
+ /** THe number of bytes in the current segment that have been written.
*/
+ private int segmentOffset;
+
+ /** THe number of bytes that have been written so far. */
+ private long globalOffset;
+
+ public ManagedMemoryOutputStream(MemorySegmentPool segmentPool, long
expectedSize)
+ throws MemoryAllocationException {
+ this.segmentPool = segmentPool;
+ this.pageSize = segmentPool.pageSize();
+ this.segmentIndex = 0;
+ this.segmentOffset = 0;
+
+ Preconditions.checkArgument(expectedSize >= 0);
+ ensureCapacity(Math.max(expectedSize, 1L));
+ }
+
+ public long getPos() {
+ return globalOffset;
+ }
+
+ public List<MemorySegment> getSegments() {
+ return segments;
+ }
+
+ @Override
+ public void write(int b) throws IOException {
+ write(new byte[] {(byte) b}, 0, 1);
+ }
+
+ @Override
+ public void write(@Nullable byte[] b, int off, int len) throws
IOException {
+ try {
+ ensureCapacity(globalOffset + len);
Review Comment:
Instead of repeatedly allocate `List<MemorySegment>` instance and do divide
operation for each write(...), would it be simpler to just maintain
`allocatedBytes` and just check `globalOffset + len <= allocatedBytes` for must
write() operation?
##########
flink-ml-iteration/src/main/java/org/apache/flink/iteration/datacache/nonkeyed/FileSegmentWriter.java:
##########
@@ -0,0 +1,89 @@
+/*
+ * 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.flink.iteration.datacache.nonkeyed;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.core.fs.FSDataOutputStream;
+import org.apache.flink.core.fs.FileSystem;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.core.memory.DataOutputView;
+import org.apache.flink.core.memory.DataOutputViewStreamWrapper;
+
+import java.io.BufferedOutputStream;
+import java.io.IOException;
+import java.util.Optional;
+
+/** A class that writes cache data to a target file in given file system. */
+@Internal
+class FileSegmentWriter<T> implements SegmentWriter<T> {
+
+ /** The tool to serialize received records into bytes. */
+ private final TypeSerializer<T> serializer;
+
+ /** The path to the target file. */
+ private final Path path;
+
+ /** The output stream that writes to the target file. */
+ private final FSDataOutputStream outputStream;
+
+ /** A buffer that wraps the output stream to optimize performance. */
+ private final BufferedOutputStream bufferedOutputStream;
+
+ /** The wrapper view of output stream to be used with TypeSerializer API.
*/
+ private final DataOutputView outputView;
+
+ /** The number of records added so far. */
+ private int count;
+
+ FileSegmentWriter(TypeSerializer<T> serializer, Path path) throws
IOException {
+ this.serializer = serializer;
+ this.path = path;
+ this.outputStream = path.getFileSystem().create(path,
FileSystem.WriteMode.NO_OVERWRITE);
+ this.bufferedOutputStream = new BufferedOutputStream(outputStream);
+ this.outputView = new
DataOutputViewStreamWrapper(bufferedOutputStream);
+ }
+
+ @Override
+ public boolean addRecord(T record) throws IOException {
+ if (outputStream.getPos() >= DataCacheWriter.MAX_SEGMENT_SIZE) {
+ return false;
+ }
+ serializer.serialize(record, outputView);
+ count++;
+ return true;
+ }
+
+ @Override
+ public Optional<Segment> finish() throws IOException {
+ this.bufferedOutputStream.flush();
Review Comment:
nits: we use `this` when the member variable name collide with the input
parameter name. This typically happen in the constructor. It looks like we
don't need to use `this` here.
##########
flink-ml-iteration/src/main/java/org/apache/flink/iteration/datacache/nonkeyed/DataCacheReader.java:
##########
@@ -20,120 +20,91 @@
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.api.java.tuple.Tuple2;
-import org.apache.flink.core.fs.FSDataInputStream;
-import org.apache.flink.core.fs.FileSystem;
-import org.apache.flink.core.memory.DataInputView;
-import org.apache.flink.core.memory.DataInputViewStreamWrapper;
import javax.annotation.Nullable;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
-/** Reads the cached data from a list of paths. */
+/** Reads the cached data from a list of segments. */
public class DataCacheReader<T> implements Iterator<T> {
+ /** The tool to deserialize bytes into records. */
private final TypeSerializer<T> serializer;
- private final FileSystem fileSystem;
-
+ /** The segments where to read the records from. */
private final List<Segment> segments;
- @Nullable private SegmentReader currentSegmentReader;
+ /** The current reader for next records. */
+ @Nullable private SegmentReader<T> currentReader;
- public DataCacheReader(
- TypeSerializer<T> serializer, FileSystem fileSystem, List<Segment>
segments)
- throws IOException {
- this(serializer, fileSystem, segments, new Tuple2<>(0, 0));
+ /** The index of the segment that current reader reads from. */
+ private int segmentIndex;
+
+ /** The number of records that have been read through current reader so
far. */
+ private int segmentCount;
+
+ public DataCacheReader(TypeSerializer<T> serializer, List<Segment>
segments) {
+ this(serializer, segments, Tuple2.of(0, 0));
}
public DataCacheReader(
TypeSerializer<T> serializer,
- FileSystem fileSystem,
List<Segment> segments,
- Tuple2<Integer, Integer> readerPosition)
- throws IOException {
-
+ Tuple2<Integer, Integer> readerPosition) {
this.serializer = serializer;
- this.fileSystem = fileSystem;
this.segments = segments;
+ this.segmentIndex = readerPosition.f0;
+ this.segmentCount = readerPosition.f1;
- if (readerPosition.f0 < segments.size()) {
- this.currentSegmentReader = new SegmentReader(readerPosition.f0,
readerPosition.f1);
- }
+ createSegmentReader(readerPosition.f0, readerPosition.f1);
Review Comment:
The `readerPosition.f1` refers to the number of records that have been read
from the `DataCache`, right?
But `createSegmentReader(...)` passes this position directly to the
`MemorySegmentReader` constructor, which interprets this value as the number of
records that should be skipped `within this segment`.
Should this inconsistency be fixed?
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