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Posted to issues@spark.apache.org by "Jose Torres (JIRA)" <ji...@apache.org> on 2017/10/09 20:55:00 UTC

[jira] [Created] (SPARK-22230) agg(last('attr)) gives weird results for streaming

Jose Torres created SPARK-22230:
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             Summary: agg(last('attr)) gives weird results for streaming
                 Key: SPARK-22230
                 URL: https://issues.apache.org/jira/browse/SPARK-22230
             Project: Spark
          Issue Type: Bug
          Components: Structured Streaming
    Affects Versions: 2.2.0
            Reporter: Jose Torres
            Priority: Minor


In stream aggregation, last('attr) yields the last value from the first microbatch forever. I'm not sure if it's fair to call this a correctness bug, since last doesn't have strong correctness semantics, but ignoring all rows past the first microbatch is at least weird.

Simple repro in StreamingAggregationSuite:

    val input = MemoryStream[Int]

    val aggregated = input.toDF().agg(last('value))
    testStream(aggregated, OutputMode.Complete())(
      AddData(input, 1, 2, 3),
      CheckLastBatch(3),
      AddData(input, 4, 5, 6),
      CheckLastBatch(6) // actually yields 3 again



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