GitHub user HyukjinKwon opened a pull request:
https://github.com/apache/spark/pull/18618
[SPARK-20090][PYTHON] Add StructType.fieldNames in PySpark
## What changes were proposed in this pull request?
This PR proposes `StructType.fieldNames` that returns immutable tuple
rather than a mutable (undocumented) `StructType.names`.
There are two points here:
- API consistency with Scala/Java
- Provide a safe way to get the field names. Manipulating these might
cause unexpected behaviour as below:
```python
from pyspark.sql.types import *
struct = StructType([StructField("f1", StringType(), True)])
names = struct.names
del names[0]
spark.createDataFrame([{"f1": 1}], struct).show()
```
```
...
java.lang.IllegalStateException: Input row doesn't have expected number
of values required by the schema. 1 fields are required while 0 values are
provided.
at
org.apache.spark.sql.execution.python.EvaluatePython$.fromJava(EvaluatePython.scala:138)
at
org.apache.spark.sql.SparkSession$$anonfun$6.apply(SparkSession.scala:741)
at
org.apache.spark.sql.SparkSession$$anonfun$6.apply(SparkSession.scala:741)
...
```
## How was this patch tested?
Added tests in `python/pyspark/sql/tests.py`.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/HyukjinKwon/spark SPARK-20090
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/18618.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 #18618
----
commit efe113fdb8f2ec7ba57766b0b87a6c8df9728291
Author: hyukjinkwon <[email protected]>
Date: 2017-07-13T02:06:44Z
Add StructType.fieldNames in PySpark
----
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