parthchandra commented on code in PR #999:
URL: https://github.com/apache/parquet-mr/pull/999#discussion_r992841047
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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:
Then it may make sense to do what the `readAllVectored` method is doing -
split each `ConsecutiveParts` into contiguous sub-ranges of 8MB (configurable).
Presumably when you merge ranges, you have a limit so you will get a large
consecutive read but not hit the memory allocation issues.
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