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Posted to commits@spark.apache.org by gu...@apache.org on 2018/01/13 07:13:49 UTC
spark git commit: [SPARK-22980][PYTHON][SQL] Clarify the length of
each series is of each batch within scalar Pandas UDF
Repository: spark
Updated Branches:
refs/heads/master 55dbfbca3 -> cd9f49a2a
[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.
Author: hyukjinkwon <gu...@gmail.com>
Closes #20237 from HyukjinKwon/SPARK-22980.
Project: http://git-wip-us.apache.org/repos/asf/spark/repo
Commit: http://git-wip-us.apache.org/repos/asf/spark/commit/cd9f49a2
Tree: http://git-wip-us.apache.org/repos/asf/spark/tree/cd9f49a2
Diff: http://git-wip-us.apache.org/repos/asf/spark/diff/cd9f49a2
Branch: refs/heads/master
Commit: cd9f49a2aed3799964976ead06080a0f7044a0c3
Parents: 55dbfbc
Author: hyukjinkwon <gu...@gmail.com>
Authored: Sat Jan 13 16:13:44 2018 +0900
Committer: hyukjinkwon <gu...@gmail.com>
Committed: Sat Jan 13 16:13:44 2018 +0900
----------------------------------------------------------------------
python/pyspark/sql/functions.py | 5 +++++
1 file changed, 5 insertions(+)
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http://git-wip-us.apache.org/repos/asf/spark/blob/cd9f49a2/python/pyspark/sql/functions.py
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diff --git a/python/pyspark/sql/functions.py b/python/pyspark/sql/functions.py
index 733e32b..e1ad659 100644
--- a/python/pyspark/sql/functions.py
+++ b/python/pyspark/sql/functions.py
@@ -2184,6 +2184,11 @@ def pandas_udf(f=None, returnType=None, functionType=None):
| 8| JOHN DOE| 22|
+----------+--------------+------------+
+ .. note:: The length of `pandas.Series` within a scalar UDF is not that of the whole input
+ column, but is the length of an internal batch used for each call to the function.
+ Therefore, this can be used, for example, to ensure the length of each returned
+ `pandas.Series`, and can not be used as the column length.
+
2. GROUP_MAP
A group map UDF defines transformation: A `pandas.DataFrame` -> A `pandas.DataFrame`
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