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[SPARK-27340][SS] Alias on TimeWindow expression cause watermark metadata lost #28326

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[SPARK-27340][SS] Alias on TimeWindow expression cause watermark metadata lost #28326

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18d1fe3
Add reproduce UT and add Liangchang as co-author
xuanyuanking Apr 24, 2020
3fd8ce2
Fix in analyzer
xuanyuanking Apr 24, 2020
05ed338
rollback
xuanyuanking Apr 27, 2020
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14 changes: 1 addition & 13 deletions sql/core/src/main/scala/org/apache/spark/sql/Column.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -972,9 +972,6 @@ class Column(val expr: Expression) extends Logging {
* df.select($"colA".as("colB"))
* }}}
*
* If the current column has metadata associated with it, this metadata will be propagated
* to the new column. If this not desired, use `as` with explicitly empty metadata.
*
* @group expr_ops
* @since 1.3.0
*/
Expand Down Expand Up @@ -1011,9 +1008,6 @@ class Column(val expr: Expression) extends Logging {
* df.select($"colA".as('colB))
* }}}
*
* If the current column has metadata associated with it, this metadata will be propagated
* to the new column. If this not desired, use `as` with explicitly empty metadata.
*
* @group expr_ops
* @since 1.3.0
*/
Expand All @@ -1040,17 +1034,11 @@ class Column(val expr: Expression) extends Logging {
* df.select($"colA".name("colB"))
* }}}
*
* If the current column has metadata associated with it, this metadata will be propagated
* to the new column. If this not desired, use `as` with explicitly empty metadata.
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@gatorsmile gatorsmile Apr 27, 2020

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Why removing these comments?

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@xuanyuanking xuanyuanking Apr 28, 2020

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These comments added together with the changes we just reverted. But it's good to have clear comments, I'll rephrase and add them back in the follow-up.

*
* @group expr_ops
* @since 2.0.0
*/
def name(alias: String): Column = withExpr {
normalizedExpr() match {
case ne: NamedExpression => Alias(expr, alias)(explicitMetadata = Some(ne.metadata))
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@cloud-fan cloud-fan Apr 27, 2020

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This was added by #8215. But looking at the added tests at that time, we just want to carry over the metadata from the child of Alias, which doesn't need this change as Alias.metedata can inherit its child's metadata.

case other => Alias(other, alias)()
}
Alias(expr, alias)()
}

/**
Expand Down
11 changes: 11 additions & 0 deletions sql/core/src/test/scala/org/apache/spark/sql/streaming/EventTimeWatermarkSuite.scala
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Expand Up @@ -593,6 +593,17 @@ class EventTimeWatermarkSuite extends StreamTest with BeforeAndAfter with Matche
}
}

test("SPARK-27340 Alias on TimeWindow expression cause watermark metadata lost") {
val inputData = MemoryStream[Int]
val aliasWindow = inputData.toDF()
.withColumn("eventTime", $"value".cast("timestamp"))
.withWatermark("eventTime", "10 seconds")
.select(window($"eventTime", "5 seconds") as 'aliasWindow)
// Check the eventTime metadata is kept in the top level alias.
assert(aliasWindow.logicalPlan.output.exists(
_.metadata.contains(EventTimeWatermark.delayKey)))
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@HeartSaVioR HeartSaVioR Apr 27, 2020

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    val windowedAggregation = aliasWindow
      .groupBy('aliasWindow)
      .agg(count("*") as 'count)
      .select($"aliasWindow".getField("start").cast("long").as[Long], $"count".as[Long])

    testStream(windowedAggregation)(
      AddData(inputData, 10, 11, 12, 13, 14, 15),
      CheckNewAnswer(),
      AddData(inputData, 25),   // Advance watermark to 15 seconds
      CheckNewAnswer((10, 5)),
      assertNumStateRows(2),
      AddData(inputData, 10),   // Should not emit anything as data less than watermark
      CheckNewAnswer(),
      assertNumStateRows(2)
    )

Let's append this to make the UT verifying E2E (yes this is same as other UTs in this suite, and the revised UT fails on master branch even without assertion to check metadata directly) - and then we no longer need to have complicated stream-stream join UT.

}

test("test no-data flag") {
val flagKey = SQLConf.STREAMING_NO_DATA_MICRO_BATCHES_ENABLED.key

Expand Down
26 changes: 26 additions & 0 deletions sql/core/src/test/scala/org/apache/spark/sql/streaming/StreamingJoinSuite.scala
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Expand Up @@ -991,4 +991,30 @@ class StreamingOuterJoinSuite extends StreamTest with StateStoreMetricsTest with
)
}
}

test("SPARK-27340 Windowed left out join with Alias on TimeWindow") {
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@dongjoon-hyun dongjoon-hyun Apr 27, 2020

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super nit. out -> outer, Let's ignore for now.

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@xuanyuanking xuanyuanking Apr 28, 2020

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Thanks, delete this test in #28390.

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@HeartSaVioR HeartSaVioR Apr 27, 2020

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I guess this is to retain the efforts of origin PR, but based on root cause, it should be pretty much easier to reproduce (and you actually did it in EventTimeWatermarkSuite).

Let's remove this test in new commit (so that we can still retain the credit) and append more code on new UT to do E2E test. I'll comment there for code we need to add.

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@xuanyuanking xuanyuanking Apr 28, 2020

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Thanks, addressed in #28390.

val (leftInput, df1) = setupStream("left", 2)
val (rightInput, df2) = setupStream("right", 3)
val left = df1.select('key, window('leftTime, "10 second") as 'leftWindow, 'leftValue)
val right = df2.select('key, window('rightTime, "10 second") as 'rightWindow, 'rightValue)
val joined = left.join(
right,
left("key") === right("key") && left("leftWindow") === right("rightWindow"),
"left_outer")
.select(left("key"), $"leftWindow.end".cast("long"), 'leftValue, 'rightValue)

testStream(joined)(
// Test inner part of the join.
MultiAddData(leftInput, 1, 2, 3, 4, 5)(rightInput, 3, 4, 5, 6, 7),
CheckNewAnswer((3, 10, 6, 9), (4, 10, 8, 12), (5, 10, 10, 15)),

MultiAddData(leftInput, 21)(rightInput, 22), // watermark = 11, no-data-batch computes nulls
CheckNewAnswer(Row(1, 10, 2, null), Row(2, 10, 4, null)),
assertNumStateRows(total = 2, updated = 12),

AddData(leftInput, 22),
CheckNewAnswer(Row(22, 30, 44, 66)),
assertNumStateRows(total = 3, updated = 1)
)
}
}