GitHub user dongjoon-hyun opened a pull request:
https://github.com/apache/spark/pull/14095
[SPARK-16429][SQL] Include `StringType` columns in Scala/Python `describe()`
## What changes were proposed in this pull request?
Currently, Spark `describe` supports `StringType`. However, Scala/Python
`describe()` returns a dataset for only all numeric columns. SparkR returns all
columns. This PR include `StringType` columns in Scala/Python `describe()`,
`describe` without argument.
**Before**
* Scala
```scala
scala>
spark.read.json("examples/src/main/resources/people.json").describe("age",
"name").show()
+-------+------------------+-------+
|summary| age| name|
+-------+------------------+-------+
| count| 2| 3|
| mean| 24.5| null|
| stddev|7.7781745930520225| null|
| min| 19| Andy|
| max| 30|Michael|
+-------+------------------+-------+
scala>
spark.read.json("examples/src/main/resources/people.json").describe().show()
+-------+------------------+
|summary| age|
+-------+------------------+
| count| 2|
| mean| 24.5|
| stddev|7.7781745930520225|
| min| 19|
| max| 30|
+-------+------------------+
```
* Python
```
>>>
spark.read.json("examples/src/main/resources/people.json").describe().show()
+-------+------------------+
|summary| age|
+-------+------------------+
| count| 2|
| mean| 24.5|
| stddev|7.7781745930520225|
| min| 19|
| max| 30|
+-------+------------------+
```
* R
```r
> collect(describe(read.json("examples/src/main/resources/people.json")))
summary age name
1 count 2 3
2 mean 24.5 <NA>
3 stddev 7.7781745930520225 <NA>
4 min 19 Andy
5 max 30 Michael
```
**After**
* Scala
```scala
scala>
spark.read.json("examples/src/main/resources/people.json").describe().show()
+-------+------------------+-------+
|summary| age| name|
+-------+------------------+-------+
| count| 2| 3|
| mean| 24.5| null|
| stddev|7.7781745930520225| null|
| min| 19| Andy|
| max| 30|Michael|
+-------+------------------+-------+
```
* Python
```
>>>
spark.read.json("examples/src/main/resources/people.json").describe().show()
+-------+------------------+-------+
|summary| age| name|
+-------+------------------+-------+
| count| 2| 3|
| mean| 24.5| null|
| stddev|7.7781745930520225| null|
| min| 19| Andy|
| max| 30|Michael|
+-------+------------------+-------+
```
* R
SparkR is the same.
## How was this patch tested?
Pass the Jenkins with a update testcase.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/dongjoon-hyun/spark SPARK-16429
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/14095.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 #14095
----
commit df2edd730216e659dbcebdcbda61dd67fbcf8d55
Author: Dongjoon Hyun <dongj...@apache.org>
Date: 2016-07-07T20:45:26Z
[SPARK-16429][SQL] Include `StringType` columns in Scala/Python `describe()`
----
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