richardstartin commented on a change in pull request #6320:
URL: https://github.com/apache/incubator-pinot/pull/6320#discussion_r536565284
##########
File path:
pinot-core/src/main/java/org/apache/pinot/core/segment/creator/impl/inv/OffHeapBitmapInvertedIndexCreator.java
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@@ -181,33 +188,49 @@ public void seal()
}
// Create bitmaps from inverted index buffers and serialize them to file
- try (DataOutputStream offsetDataStream = new DataOutputStream(
- new BufferedOutputStream(new FileOutputStream(_invertedIndexFile)));
- FileOutputStream bitmapFileStream = new
FileOutputStream(_invertedIndexFile);
- DataOutputStream bitmapDataStream = new DataOutputStream(new
BufferedOutputStream(bitmapFileStream))) {
- int bitmapOffset = (_cardinality + 1) * Integer.BYTES;
- offsetDataStream.writeInt(bitmapOffset);
- bitmapFileStream.getChannel().position(bitmapOffset);
-
+ ByteBuffer offsetBuffer = null;
+ ByteBuffer bitmapBuffer = null;
+ try (FileChannel channel = new RandomAccessFile(_invertedIndexFile,
"rw").getChannel()) {
Review comment:
Two places.
- We found that serializing to `ByteBuffer` could be up to 20x faster than
to `DataOutput`, which was why the API was added.
- If the bitmaps being materialised prior to serialisation below get
reasonably large, using `RoaringBitmapWriter` improves the efficiency of
construction. This is because when you call `RoaringBitmap.add`, it does a
binary search in the high 16 bits of the value to figure out where to put the
low 16 bits, but `RoaringBitmapWriter` assumes all adds are appends and
optimises for it.
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