Prasanth J created HIVE-6287:
--------------------------------
Summary: batchSize computation in Vectorized ORC reader can cause
BufferUnderFlowException when PPD is enabled
Key: HIVE-6287
URL: https://issues.apache.org/jira/browse/HIVE-6287
Project: Hive
Issue Type: Bug
Components: Vectorization
Affects Versions: 0.13.0
Reporter: Prasanth J
Assignee: Prasanth J
Attachments: HIVE-6287.WIP.patch
nextBatch() method that computes the batchSize is only aware of stripe
boundaries. This will not work when PPD in ORC is enabled as PPD works at row
group level (stripe contains multiple row groups). By default, row group stride
is 10000. When PPD is enabled, some row groups may get eliminated. After row
group elimination, disk ranges are computed based on the selected row groups.
If batchSize computation is not aware of this, it will lead to
BufferUnderFlowException (reading beyond disk range). Following scenario should
illustrate it more clearly
{code}
|--------------------------------- STRIPE 1
------------------------------------|
|-- row grp 1 --|-- row grp 2 --|-- row grp 3 --|-- row grp 4 --|-- row grp 5
--|
|--------- diskrange 1 ---------| |- diskrange 2
-|
^
(marker)
{code}
diskrange1 will have 20000 rows and diskrange 2 will have 10000 rows. Since
nextBatch() was not aware of row groups and hence the diskranges, it tries to
read 1024 values from the end of diskrange 1 where it should only read 20000 %
1024 = 544 values. This will result in BufferUnderFlowException.
To fix this, a marker is placed at the end of each range and batchSize is
computed accordingly. {code}batchSize =
Math.min(VectorizedRowBatch.DEFAULT_SIZE, (markerPosition - rowInStripe));{code}
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