GitHub user dongjoon-hyun opened a pull request:
https://github.com/apache/spark/pull/15317
[SPARK-17739][SQL] Collapse adjacent similar Window operators
## What changes were proposed in this pull request?
Currently, Spark does not collapse adjacent windows with the same
partitioning and sorting. This PR implements `CollapseWindow` optimizer to
solve that.
For example:
```
val df = spark.range(1000).select($"id" % 100 as "grp", $"id", rand() as
"col1", rand() as "col2")
// Add summary statistics for all columns
import org.apache.spark.sql.expressions.Window
val cols = Seq("id", "col1", "col2")
val window = Window.partitionBy($"grp").orderBy($"id")
val result = cols.foldLeft(df) { (base, name) =>
base.withColumn(s"${name}_avg", avg(col(name)).over(window))
.withColumn(s"${name}_stddev", stddev(col(name)).over(window))
.withColumn(s"${name}_min", min(col(name)).over(window))
.withColumn(s"${name}_max", max(col(name)).over(window))
}
```
**Before**
```
scala> result.explain
== Physical Plan ==
Window [max(col2#19) windowspecdefinition(grp#17L, id#14L ASC NULLS FIRST,
RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS col2_max#234], [grp#17L],
[id#14L ASC NULLS FIRST]
+- Window [min(col2#19) windowspecdefinition(grp#17L, id#14L ASC NULLS
FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS col2_min#216],
[grp#17L], [id#14L ASC NULLS FIRST]
+- Window [stddev_samp(col2#19) windowspecdefinition(grp#17L, id#14L ASC
NULLS FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS
col2_stddev#191], [grp#17L], [id#14L ASC NULLS FIRST]
+- Window [avg(col2#19) windowspecdefinition(grp#17L, id#14L ASC
NULLS FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS
col2_avg#167], [grp#17L], [id#14L ASC NULLS FIRST]
+- Window [max(col1#18) windowspecdefinition(grp#17L, id#14L ASC
NULLS FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS
col1_max#152], [grp#17L], [id#14L ASC NULLS FIRST]
+- Window [min(col1#18) windowspecdefinition(grp#17L, id#14L
ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS
col1_min#138], [grp#17L], [id#14L ASC NULLS FIRST]
+- Window [stddev_samp(col1#18)
windowspecdefinition(grp#17L, id#14L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW) AS col1_stddev#117], [grp#17L], [id#14L ASC NULLS
FIRST]
+- Window [avg(col1#18) windowspecdefinition(grp#17L,
id#14L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS
col1_avg#97], [grp#17L], [id#14L ASC NULLS FIRST]
+- Window [max(id#14L) windowspecdefinition(grp#17L,
id#14L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS
id_max#86L], [grp#17L], [id#14L ASC NULLS FIRST]
+- Window [min(id#14L)
windowspecdefinition(grp#17L, id#14L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW) AS id_min#76L], [grp#17L], [id#14L ASC NULLS FIRST]
+- *Project [grp#17L, id#14L, col1#18, col2#19,
id_avg#26, id_stddev#42]
+- Window [stddev_samp(_w0#59)
windowspecdefinition(grp#17L, id#14L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW) AS id_stddev#42], [grp#17L], [id#14L ASC NULLS FIRST]
+- *Project [grp#17L, id#14L, col1#18,
col2#19, id_avg#26, cast(id#14L as double) AS _w0#59]
+- Window [avg(id#14L)
windowspecdefinition(grp#17L, id#14L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW) AS id_avg#26], [grp#17L], [id#14L ASC NULLS FIRST]
+- *Sort [grp#17L ASC NULLS FIRST,
id#14L ASC NULLS FIRST], false, 0
+- Exchange
hashpartitioning(grp#17L, 200)
+- *Project [(id#14L % 100) AS
grp#17L, id#14L, rand(-6329949029880411066) AS col1#18,
rand(-7251358484380073081) AS col2#19]
+- *Range (0, 1000, step=1,
splits=Some(8))
```
**After**
```
scala> result.explain
== Physical Plan ==
Window [max(col2#5) windowspecdefinition(grp#3L, id#0L ASC NULLS FIRST,
RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS col2_max#220, min(col2#5)
windowspecdefinition(grp#3L, id#0L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW) AS col2_min#202, stddev_samp(col2#5)
windowspecdefinition(grp#3L, id#0L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW) AS col2_stddev#177, avg(col2#5)
windowspecdefinition(grp#3L, id#0L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW) AS col2_avg#153, max(col1#4)
windowspecdefinition(grp#3L, id#0L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW) AS col1_max#138, min(col1#4)
windowspecdefinition(grp#3L, id#0L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW) AS col1_min#124, stddev_samp(col1#4)
windowspecdefinition(grp#3L, id#0L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW) AS col1_stddev#103, avg(col1#4)
windowspecdefinition(grp#3L,
id#0L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS
col1_avg#83, max(id#0L) windowspecdefinition(grp#3L, id#0L ASC NULLS FIRST,
RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS id_max#72L, min(id#0L)
windowspecdefinition(grp#3L, id#0L ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW) AS id_min#62L], [grp#3L], [id#0L ASC NULLS FIRST]
+- *Project [grp#3L, id#0L, col1#4, col2#5, id_avg#12, id_stddev#28]
+- Window [stddev_samp(_w0#45) windowspecdefinition(grp#3L, id#0L ASC
NULLS FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS
id_stddev#28], [grp#3L], [id#0L ASC NULLS FIRST]
+- *Project [grp#3L, id#0L, col1#4, col2#5, id_avg#12, cast(id#0L as
double) AS _w0#45]
+- Window [avg(id#0L) windowspecdefinition(grp#3L, id#0L ASC NULLS
FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS id_avg#12],
[grp#3L], [id#0L ASC NULLS FIRST]
+- *Sort [grp#3L ASC NULLS FIRST, id#0L ASC NULLS FIRST],
false, 0
+- Exchange hashpartitioning(grp#3L, 200)
+- *Project [(id#0L % 100) AS grp#3L, id#0L,
rand(6537478539664068821) AS col1#4, rand(-8961093871295252795) AS col2#5]
+- *Range (0, 1000, step=1, splits=Some(8))
```
## How was this patch tested?
Pass the Jenkins tests with a newly added testsuite.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/dongjoon-hyun/spark SPARK-17739
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/15317.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #15317
----
commit 2d682b8cf110e16b98982d824fb298d5dc3d2094
Author: Dongjoon Hyun <[email protected]>
Date: 2016-09-30T22:02:36Z
[SPARK-17739][SQL] Collapse adjacent similar Window operators
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