GitHub user HyukjinKwon opened a pull request:
https://github.com/apache/spark/pull/20237
[SPARK-22980][PYTHON][SQL] Clarify the length of each series is of each
batch within scalar Pandas UDF
## What changes were proposed in this pull request?
This PR proposes to add a note that saying the length of a scalar Pandas
UDF's `Series` is not of the whole input column but of the batch.
We are fine for a group map UDF because the usage is different from our
typical UDF but scalar UDFs might cause confusion with the normal UDF.
For example, please consider this example:
```python
from pyspark.sql.functions import pandas_udf, col, lit
df = spark.range(1)
f = pandas_udf(lambda x, y: len(x) + y, LongType())
df.select(f(lit('text'), col('id'))).show()
```
```
+------------------+
|<lambda>(text, id)|
+------------------+
| 1|
+------------------+
```
```python
from pyspark.sql.functions import udf, col, lit
df = spark.range(1)
f = udf(lambda x, y: len(x) + y, "long")
df.select(f(lit('text'), col('id'))).show()
```
```
+------------------+
|<lambda>(text, id)|
+------------------+
| 4|
+------------------+
```
## How was this patch tested?
Manually built the doc and checked the output.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/HyukjinKwon/spark SPARK-22980
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/20237.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 #20237
----
commit d2cfed308d343fb55c5fd7c0d30bcbb987948632
Author: hyukjinkwon <gurwls223@...>
Date: 2018-01-11T15:31:05Z
Clarify the length of each series is of each batch within scalar Pandas UDF
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