Zoltán Borók-Nagy created IMPALA-10135:
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Summary: Insert events doesn't contain the inserted data files
Key: IMPALA-10135
URL: https://issues.apache.org/jira/browse/IMPALA-10135
Project: IMPALA
Issue Type: Bug
Reporter: Zoltán Borók-Nagy
When Impala generates INSERT EVENTs it doesn't add the newly inserted datafiles.
The problem is that Impala misuses Sets.difference(set1, set2). From the API
doc at
[https://guava.dev/releases/28.2-jre/api/docs/com/google/common/collect/Sets.html#difference-java.util.Set-java.util.Set-]
"The returned set contains all elements that are contained by {{set1}} and not
contained by {{set2}}. {{set2}} may also contain elements not present in
{{set1}}; these are simply ignored."
So the name "difference" is a bit misleading, its rather a subtraction between
set1 and set2.
Unfortunately Impala passes the parameters in wrong order:
Sets.difference(beforeInsert, afterInsert):
[https://github.com/apache/impala/blob/4cb3c3556e77ee24003383155ca5e1b70be4db6e/fe/src/main/java/org/apache/impala/service/CatalogOpExecutor.java#L4581]
So the result will be always empty.
There's another problem with INSERT OVERWRITEs, in that case we never fill the
data files of the insert event.
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