[
https://issues.apache.org/jira/browse/DRILL-5546?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16146649#comment-16146649
]
ASF GitHub Bot commented on DRILL-5546:
---------------------------------------
Github user jinfengni commented on a diff in the pull request:
https://github.com/apache/drill/pull/906#discussion_r135974133
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/project/ProjectRecordBatch.java
---
@@ -768,4 +765,73 @@ else if (exprHasPrefix && refHasPrefix) {
}
}
}
+
+ /**
+ * handle FAST NONE specially when Project for query output. This
happens when input returns a
+ * FAST NONE directly ( input does not return any batch with
schema/data).
+ *
+ * Project operator has to return a batch with schema derived using the
following 3 rules:
+ * Case 1: * ==> expand into an empty list of columns.
+ * Case 2: regular column reference ==> treat as nullable-int column
+ * Case 3: expressions => Call ExpressionTreeMaterialization over an
empty vector contain.
--- End diff --
Done.
> Schema change problems caused by empty batch
> --------------------------------------------
>
> Key: DRILL-5546
> URL: https://issues.apache.org/jira/browse/DRILL-5546
> Project: Apache Drill
> Issue Type: Bug
> Reporter: Jinfeng Ni
> Assignee: Jinfeng Ni
>
> There have been a few JIRAs opened related to schema change failure caused by
> empty batch. This JIRA is opened as an umbrella for all those related JIRAS (
> such as DRILL-4686, DRILL-4734, DRILL4476, DRILL-4255, etc).
>
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
