Github user wselwood commented on the issue:
https://github.com/apache/spark/pull/18088
Good catch @HyukjinKwon Sorry about that.
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GitHub user wselwood opened a pull request:
https://github.com/apache/spark/pull/18088
[Minor] document edge case of updateFunc usage
## What changes were proposed in this pull request?
Include documentation of the fact that the updateFunc is sometimes called
with no new
