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[SPARK-44871][SQL][3.4] Fix percentile_disc behaviour#42610

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[SPARK-44871][SQL][3.4] Fix percentile_disc behaviour#42610
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peter-toth:SPARK-44871-fix-percentile-disc-behaviour-3.4

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What changes were proposed in this pull request?

This PR fixes percentile_disc() function as currently it returns inforrect results in some cases. E.g.:

SELECT
  percentile_disc(0.0) WITHIN GROUP (ORDER BY a) as p0,
  percentile_disc(0.1) WITHIN GROUP (ORDER BY a) as p1,
  percentile_disc(0.2) WITHIN GROUP (ORDER BY a) as p2,
  percentile_disc(0.3) WITHIN GROUP (ORDER BY a) as p3,
  percentile_disc(0.4) WITHIN GROUP (ORDER BY a) as p4,
  percentile_disc(0.5) WITHIN GROUP (ORDER BY a) as p5,
  percentile_disc(0.6) WITHIN GROUP (ORDER BY a) as p6,
  percentile_disc(0.7) WITHIN GROUP (ORDER BY a) as p7,
  percentile_disc(0.8) WITHIN GROUP (ORDER BY a) as p8,
  percentile_disc(0.9) WITHIN GROUP (ORDER BY a) as p9,
  percentile_disc(1.0) WITHIN GROUP (ORDER BY a) as p10
FROM VALUES (0), (1), (2), (3), (4) AS v(a)

currently returns:

+---+---+---+---+---+---+---+---+---+---+---+
| p0| p1| p2| p3| p4| p5| p6| p7| p8| p9|p10|
+---+---+---+---+---+---+---+---+---+---+---+
|0.0|0.0|0.0|1.0|1.0|2.0|2.0|2.0|3.0|3.0|4.0|
+---+---+---+---+---+---+---+---+---+---+---+

but after this PR it returns the correct:

+---+---+---+---+---+---+---+---+---+---+---+
| p0| p1| p2| p3| p4| p5| p6| p7| p8| p9|p10|
+---+---+---+---+---+---+---+---+---+---+---+
|0.0|0.0|0.0|1.0|1.0|2.0|2.0|3.0|3.0|4.0|4.0|
+---+---+---+---+---+---+---+---+---+---+---+

Why are the changes needed?

Bugfix.

Does this PR introduce any user-facing change?

Yes, fixes a correctness bug, but the old behaviour can be restored with spark.sql.legacy.percentileDiscCalculation=true.

How was this patch tested?

Added new UTs.

This PR fixes `percentile_disc()` function as currently it returns inforrect results in some cases. E.g.:
```
SELECT
  percentile_disc(0.0) WITHIN GROUP (ORDER BY a) as p0,
  percentile_disc(0.1) WITHIN GROUP (ORDER BY a) as p1,
  percentile_disc(0.2) WITHIN GROUP (ORDER BY a) as p2,
  percentile_disc(0.3) WITHIN GROUP (ORDER BY a) as p3,
  percentile_disc(0.4) WITHIN GROUP (ORDER BY a) as p4,
  percentile_disc(0.5) WITHIN GROUP (ORDER BY a) as p5,
  percentile_disc(0.6) WITHIN GROUP (ORDER BY a) as p6,
  percentile_disc(0.7) WITHIN GROUP (ORDER BY a) as p7,
  percentile_disc(0.8) WITHIN GROUP (ORDER BY a) as p8,
  percentile_disc(0.9) WITHIN GROUP (ORDER BY a) as p9,
  percentile_disc(1.0) WITHIN GROUP (ORDER BY a) as p10
FROM VALUES (0), (1), (2), (3), (4) AS v(a)
```
currently returns:
```
+---+---+---+---+---+---+---+---+---+---+---+
| p0| p1| p2| p3| p4| p5| p6| p7| p8| p9|p10|
+---+---+---+---+---+---+---+---+---+---+---+
|0.0|0.0|0.0|1.0|1.0|2.0|2.0|2.0|3.0|3.0|4.0|
+---+---+---+---+---+---+---+---+---+---+---+
```
but after this PR it returns the correct:
```
+---+---+---+---+---+---+---+---+---+---+---+
| p0| p1| p2| p3| p4| p5| p6| p7| p8| p9|p10|
+---+---+---+---+---+---+---+---+---+---+---+
|0.0|0.0|0.0|1.0|1.0|2.0|2.0|3.0|3.0|4.0|4.0|
+---+---+---+---+---+---+---+---+---+---+---+
```

Bugfix.

Yes, fixes a correctness bug, but the old behaviour can be restored with `spark.sql.legacy.percentileDiscCalculation=true`.

Added new UTs.

Closes apache#42559 from peter-toth/SPARK-44871-fix-percentile-disc-behaviour.

Authored-by: Peter Toth <peter.toth@gmail.com>
Signed-off-by: Peter Toth <peter.toth@gmail.com>
@MaxGekk

MaxGekk commented Aug 22, 2023

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+1, LGTM. Merging to 3.4.
Thank you, @peter-toth and @cloud-fan for review.

MaxGekk pushed a commit that referenced this pull request Aug 22, 2023
### What changes were proposed in this pull request?
This PR fixes `percentile_disc()` function as currently it returns inforrect results in some cases. E.g.:
```
SELECT
  percentile_disc(0.0) WITHIN GROUP (ORDER BY a) as p0,
  percentile_disc(0.1) WITHIN GROUP (ORDER BY a) as p1,
  percentile_disc(0.2) WITHIN GROUP (ORDER BY a) as p2,
  percentile_disc(0.3) WITHIN GROUP (ORDER BY a) as p3,
  percentile_disc(0.4) WITHIN GROUP (ORDER BY a) as p4,
  percentile_disc(0.5) WITHIN GROUP (ORDER BY a) as p5,
  percentile_disc(0.6) WITHIN GROUP (ORDER BY a) as p6,
  percentile_disc(0.7) WITHIN GROUP (ORDER BY a) as p7,
  percentile_disc(0.8) WITHIN GROUP (ORDER BY a) as p8,
  percentile_disc(0.9) WITHIN GROUP (ORDER BY a) as p9,
  percentile_disc(1.0) WITHIN GROUP (ORDER BY a) as p10
FROM VALUES (0), (1), (2), (3), (4) AS v(a)
```
currently returns:
```
+---+---+---+---+---+---+---+---+---+---+---+
| p0| p1| p2| p3| p4| p5| p6| p7| p8| p9|p10|
+---+---+---+---+---+---+---+---+---+---+---+
|0.0|0.0|0.0|1.0|1.0|2.0|2.0|2.0|3.0|3.0|4.0|
+---+---+---+---+---+---+---+---+---+---+---+
```
but after this PR it returns the correct:
```
+---+---+---+---+---+---+---+---+---+---+---+
| p0| p1| p2| p3| p4| p5| p6| p7| p8| p9|p10|
+---+---+---+---+---+---+---+---+---+---+---+
|0.0|0.0|0.0|1.0|1.0|2.0|2.0|3.0|3.0|4.0|4.0|
+---+---+---+---+---+---+---+---+---+---+---+
```

### Why are the changes needed?
Bugfix.

### Does this PR introduce _any_ user-facing change?
Yes, fixes a correctness bug, but the old behaviour can be restored with `spark.sql.legacy.percentileDiscCalculation=true`.

### How was this patch tested?
Added new UTs.

Closes #42610 from peter-toth/SPARK-44871-fix-percentile-disc-behaviour-3.4.

Authored-by: Peter Toth <peter.toth@gmail.com>
Signed-off-by: Max Gekk <max.gekk@gmail.com>
@MaxGekk MaxGekk closed this Aug 22, 2023
viirya pushed a commit to viirya/spark-1 that referenced this pull request Oct 19, 2023
This PR fixes `percentile_disc()` function as currently it returns inforrect results in some cases. E.g.:
```
SELECT
  percentile_disc(0.0) WITHIN GROUP (ORDER BY a) as p0,
  percentile_disc(0.1) WITHIN GROUP (ORDER BY a) as p1,
  percentile_disc(0.2) WITHIN GROUP (ORDER BY a) as p2,
  percentile_disc(0.3) WITHIN GROUP (ORDER BY a) as p3,
  percentile_disc(0.4) WITHIN GROUP (ORDER BY a) as p4,
  percentile_disc(0.5) WITHIN GROUP (ORDER BY a) as p5,
  percentile_disc(0.6) WITHIN GROUP (ORDER BY a) as p6,
  percentile_disc(0.7) WITHIN GROUP (ORDER BY a) as p7,
  percentile_disc(0.8) WITHIN GROUP (ORDER BY a) as p8,
  percentile_disc(0.9) WITHIN GROUP (ORDER BY a) as p9,
  percentile_disc(1.0) WITHIN GROUP (ORDER BY a) as p10
FROM VALUES (0), (1), (2), (3), (4) AS v(a)
```
currently returns:
```
+---+---+---+---+---+---+---+---+---+---+---+
| p0| p1| p2| p3| p4| p5| p6| p7| p8| p9|p10|
+---+---+---+---+---+---+---+---+---+---+---+
|0.0|0.0|0.0|1.0|1.0|2.0|2.0|2.0|3.0|3.0|4.0|
+---+---+---+---+---+---+---+---+---+---+---+
```
but after this PR it returns the correct:
```
+---+---+---+---+---+---+---+---+---+---+---+
| p0| p1| p2| p3| p4| p5| p6| p7| p8| p9|p10|
+---+---+---+---+---+---+---+---+---+---+---+
|0.0|0.0|0.0|1.0|1.0|2.0|2.0|3.0|3.0|4.0|4.0|
+---+---+---+---+---+---+---+---+---+---+---+
```

Bugfix.

Yes, fixes a correctness bug, but the old behaviour can be restored with `spark.sql.legacy.percentileDiscCalculation=true`.

Added new UTs.

Closes apache#42610 from peter-toth/SPARK-44871-fix-percentile-disc-behaviour-3.4.

Authored-by: Peter Toth <peter.toth@gmail.com>
Signed-off-by: Max Gekk <max.gekk@gmail.com>
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3 participants