parthchandra commented on code in PR #999:
URL: https://github.com/apache/parquet-mr/pull/999#discussion_r993981829
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parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java:
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@@ -1093,10 +1099,38 @@ private ColumnChunkPageReadStore
internalReadFilteredRowGroup(BlockMetaData bloc
}
}
}
- // actually read all the chunks
+ // Vectored IO up.
+
+ List<FileRange> ranges = new ArrayList<>();
for (ConsecutivePartList consecutiveChunks : allParts) {
- consecutiveChunks.readAll(f, builder);
+ ranges.add(FileRange.createFileRange(consecutiveChunks.offset, (int)
consecutiveChunks.length));
+ }
+ LOG.warn("Doing vectored IO for ranges {}", ranges);
+ f.readVectored(ranges, ByteBuffer::allocate);
Review Comment:
So if I have something like this -
`range 1, delta 1, range2`
I will give you two ranges, `range1`, and `range2` separated by a gap of
`delta1` bytes. If `delta1` is small enough, you will merge `range1` and
`range2` and do a single scan.
If `range1` and `range2` are very large so that the resulting range is even
larger, do you still do a single scan, or do you split the large range into
smaller ranges and tradeoff some seek cost for increased parallelism?
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