viirya opened a new pull request #35521:
URL: https://github.com/apache/spark/pull/35521
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### What changes were proposed in this pull request?
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This change proposes to change how streaming `dropDuplicates` handles keys
in its states. Currently if no watermark column in dedup keys, the states are
kept in the operator's state store and won't be removed at all. This change
proposes to remove states which are expired on watermark.
### Why are the changes needed?
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Currently streaming `dropDuplicates` simply stores all states forever if no
watermark-attached key exists.
For streaming stateful operator, this seems counterintuitive behavior if we
consider other stateful operations such as streaming joining.
It also means the number of state will grow up infinitely as we observe in
real application. But it doesn't make sense to add a time column into dedup
keys because we don't really deduplicate rows by [key, time] but only by [key].
More reasonable streaming dedup seems to remove out-of-watermark states if
the input data (not key) has watermark. Note that, unfortunately, this will be
a behavior change, for streaming queries with dedup operation.
### Does this PR introduce _any_ user-facing change?
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Yes. The state value format will be changed for streaming dedup. This is
also a behavior change for streaming dedup.
### How was this patch tested?
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Added test.
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