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https://issues.apache.org/jira/browse/DRILL-5344?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15905988#comment-15905988
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ASF GitHub Bot commented on DRILL-5344:
---------------------------------------
Github user Ben-Zvi commented on a diff in the pull request:
https://github.com/apache/drill/pull/778#discussion_r105520793
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/xsort/managed/PriorityQueueCopierTemplate.java
---
@@ -57,9 +57,12 @@ public void setup(FragmentContext context,
BufferAllocator allocator, VectorAcce
queueSize = 0;
for (int i = 0; i < size; i++) {
- vector4.set(i, i, batchGroups.get(i).getNextIndex());
- siftUp();
- queueSize++;
+ int index = batchGroups.get(i).getNextIndex();
+ vector4.set(i, i, index);
--- End diff --
If the record batch is empty, why set this (65535) value in the vector ?
Probably usually the empty batch is last, so queueSize would not be
incremented; otherwise if the next iteration brings a non empty batch, then
siftUp() may run into that 65535 .... (not sure ...)
> External sort priority queue copier fails with an empty batch
> -------------------------------------------------------------
>
> Key: DRILL-5344
> URL: https://issues.apache.org/jira/browse/DRILL-5344
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.10.0
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Priority: Minor
> Fix For: 1.11.0
>
>
> The external sort uses a "priority queue copier" to merge batches when
> spilling or when merging spilled batches.
> The code will fail with an {{IndexOutOfBoundsException}} if any record batch
> is empty. The reason is a faulty assumption in generated code:
> {code}
> public void setup(...) {
> ...
> vector4.set(i, i, batchGroups.get(i).getNextIndex());
> ...
> }
> public int getNextIndex() {
> if (pointer == getRecordCount()) {
> return -1;
> }
> ...
> }
> {code}
> The code to get the next index returns -1 when the "position" in a record
> batch is zero. The -1 position translates (when truncated) into 65535 which
> produces the index exception.
> The workaround has been to special case empty batches elsewhere in the code,
> apparently to avoid hitting this error.
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