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https://issues.apache.org/jira/browse/DRILL-5839?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16193607#comment-16193607
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ASF GitHub Bot commented on DRILL-5839:
---------------------------------------
Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/974#discussion_r143049947
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/store/mock/MockRecordReader.java
---
@@ -52,7 +52,7 @@ public MockRecordReader(FragmentContext context,
MockScanEntry config) {
private int getEstimatedRecordSize(MockColumn[] types) {
int x = 0;
- for (int i = 0; i < types.length; i++) {
+ for (int i = 0; i < (types == null ? 0 : types.length); i++) {
--- End diff --
Nit: maybe use:
```
if (types == null) { return 0; }
// Original code here..
```
> Handle Empty Batches in Merge Receiver
> --------------------------------------
>
> Key: DRILL-5839
> URL: https://issues.apache.org/jira/browse/DRILL-5839
> Project: Apache Drill
> Issue Type: Bug
> Components: Execution - Flow
> Affects Versions: 1.11.0
> Reporter: Padma Penumarthy
> Assignee: Padma Penumarthy
> Fix For: 1.12.0
>
>
> merge receiver throws an exception when it receives first batch as empty
> batch (no rows and no schema) from any of the senders. Problem is that the
> operator expects at least one batch with schema (0 rows is ok, 0 columns is
> not) from each of its senders.
> The way algorithm works is as follows:
> Get the first batch from each of the senders.
> Create hyper vector container with this first batch from each of the senders.
> Add the batches from senders to the priority queue
> Pop from priority queue, get the index for the current batch from that
> sender,
> and use that to copy from the hyper vector to the outgoing vector
> When the end of batch from a sender is reached, load the next batch from the
> sender.
> Stop when there are no more batches from any of the senders.
> If any of the senders do not send first batch with schema and if we skip
> adding that batch to the hyper vector, hyper vector is not setup correctly
> and all the offsets from selection vector to individual batches from senders
> with in the hyper vector are messed up.
> Fix for this problem is when we receive empty batch from any of the senders,
> create dummy batch with schema from one of the other senders and add it to
> the hyper vector.
> If all senders send empty first batches, we just return NONE to downstream
> operator.
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