reading a xml file in Pyspark-CodePudding

I have a spark session opened and a directory with a .xml file on it. I just want to read the schema of the .xml file but I guess spark doesn´t do it directly as if, for example, I want to read a parquet.

I mean, I´m trying to do something like:

path = "/.../.../.../filename.xml"
df_xml = spark.read.format("xml").option("rowTag", "<the rowTag name here>").load(path)
df_xml.printSchema()

What I got is:

File "/opt/mapr/spark/spark-2.4.4/python/pyspark/sql/readwriter.py", line 166, in load
    return self._df(self._jreader.load(path))
  File "/opt/mapr/spark/spark-2.4.4/python/lib/py4j-0.10.7-src.zip/py4j/java_gateway.py", line 1257, in __call__
  File "/opt/mapr/spark/spark-2.4.4/python/pyspark/sql/utils.py", line 63, in deco
    return f(*a, **kw)
  File "/opt/mapr/spark/spark-2.4.4/python/lib/py4j-0.10.7-src.zip/py4j/protocol.py", line 328, in get_return_value
py4j.protocol.Py4JJavaError: An error occurred while calling o92.load.
: java.lang.ClassNotFoundException: Failed to find data source: xml. 

Caused by: java.lang.ClassNotFoundException: xml.DefaultSource

Has anyone try to read the schema of a xml file in pyspark? I´m new on this, I´ll really appreciate your feedback.

CodePudding user response：

Parquet format contains information about the schema, XML doesn't. You can't just read the schema without inferring it from the data.

Since I don't have information about your XML file I'll use this sample: XML Sample File

Save that XML sample to sample.xml and you'll have to specify the Spark XML package in order to parse the XML file.

Here's the example:

from pyspark.sql import SparkSession

if __name__ == "__main__":
    spark = SparkSession \
        .builder \
        .appName("Test") \
        .config("spark.jars.packages", "com.databricks:spark-xml_2.12:0.13.0") \
        .getOrCreate()

    df = spark.read.format('xml').options(rowTag='catalog').load('sample.xml')
    df.printSchema()

The result is:

root
 |-- book: array (nullable = true)
 |    |-- element: struct (containsNull = true)
 |    |    |-- _id: string (nullable = true)
 |    |    |-- author: string (nullable = true)
 |    |    |-- description: string (nullable = true)
 |    |    |-- genre: string (nullable = true)
 |    |    |-- price: double (nullable = true)
 |    |    |-- publish_date: date (nullable = true)
 |    |    |-- title: string (nullable = true)