richardstartin commented on a change in pull request #6320:
URL: https://github.com/apache/incubator-pinot/pull/6320#discussion_r536910850
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File path:
pinot-core/src/main/java/org/apache/pinot/core/segment/creator/impl/inv/OffHeapBitmapInvertedIndexCreator.java
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@@ -181,33 +188,51 @@ 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()) {
+ // map the offsets buffer
+ final int startOfBitmaps = (_cardinality + 1) * Integer.BYTES;
+ int bitmapOffset = startOfBitmaps;
+ offsetBuffer = channel.map(FileChannel.MapMode.READ_WRITE, 0,
bitmapOffset).order(LITTLE_ENDIAN);
+ offsetBuffer.putInt(reverseBytes(bitmapOffset));
+ RoaringBitmap[] bitmaps = new RoaringBitmap[_cardinality];
Review comment:
> Do RoaringBitmap and MutableRoaringBitmap serialize to the same bytes?
Yes, they do.
> For off-heap creator, we don't want to keep all bitmaps on heap. We should
try to create and serialize the bitmaps one by one. Not sure about the cost if
we map a buffer per bitmap
I can see the incentive not to allocate so much on heap, but the alternative
is mapping many times (and it's a relatively costly operation) or mapping too
many bytes and truncating the channel. I have done the latter in the past to
get round this, but there may be downsides I'm unaware of. I've updated to use
this strategy and allocation pressure is indeed reduced.
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