## What changes were proposed in this pull request?
For some datasources which are based on HadoopRDD or NewHadoopRDD, such as spark-xml, InputFileBlockHolder doesn't work with Python UDF.
The method to reproduce it is, running the following codes with `bin/pyspark --packages com.databricks:spark-xml_2.11:0.4.1`:
from pyspark.sql.functions import udf,input_file_name
from pyspark.sql.types import StringType
from pyspark.sql import SparkSession
def filename(path):
return path
session = SparkSession.builder.appName('APP').getOrCreate()
session.udf.register('sameText', filename)
sameText = udf(filename, StringType())
df = session.read.format('xml').load('a.xml', rowTag='root').select('*', input_file_name().alias('file'))
df.select('file').show() # works
df.select(sameText(df['file'])).show() # returns empty content
The issue is because in `HadoopRDD` and `NewHadoopRDD` we set the file block's info in `InputFileBlockHolder` before the returned iterator begins consuming. `InputFileBlockHolder` will record this info into thread local variable. When running Python UDF in batch, we set up another thread to consume the iterator from child plan's output rdd, so we can't read the info back in another thread.
To fix this, we have to set the info in `InputFileBlockHolder` after the iterator begins consuming. So the info can be read in correct thread.
## How was this patch tested?
Manual test with above example codes for spark-xml package on pyspark: `bin/pyspark --packages com.databricks:spark-xml_2.11:0.4.1`.
Added pyspark test.
Please review http://spark.apache.org/contributing.html before opening a pull request.
Author: Liang-Chi Hsieh <viirya@gmail.com>
Closes#16585 from viirya/fix-inputfileblock-hadooprdd.
d06172b88e