[SPARK-23004][SS] Ensure StateStore.commit is called only once in a streaming aggregation task #21124
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What changes were proposed in this pull request?
A structured streaming query with a streaming aggregation can throw the following error in rare cases.
This can happen when the following conditions are accidentally hit.
TypedImperativeAggregation
(for example,collect_set
,collect_list
,percentile
, etc.).update}
modeThis causes StateStore.commit to be called twice. See the JIRA for a more detailed explanation. The solution is to use
NextIterator
orCompletionIterator
, each of which has a flag to prevent the "onCompletion" task from being called more than once. In this PR, I chose to implement usingNextIterator
.How was this patch tested?
Added unit test that I have confirm will fail without the fix.