Ondrej Kokes created SPARK-22236:
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Summary: CSV I/O: does not respect RFC 4180
Key: SPARK-22236
URL: https://issues.apache.org/jira/browse/SPARK-22236
Project: Spark
Issue Type: Improvement
Components: Input/Output
Affects Versions: 2.2.0
Reporter: Ondrej Kokes
Priority: Minor
When reading or writing CSV files with Spark, double quotes are escaped with a
backslash by default. However, the appropriate behaviour as set out by RFC 4180
(and adhered to by many software packages) is to escape using a second double
quote.
This piece of Python code demonstrates the issue
{code}
import csv
with open('testfile.csv', 'w') as f:
cw = csv.writer(f)
cw.writerow(['a 2.5" drive', 'another column'])
cw.writerow(['a "quoted" string', '"quoted"'])
cw.writerow([1,2])
with open('testfile.csv') as f:
print(f.read())
# "a 2.5"" drive",another column
# "a ""quoted"" string","""quoted"""
# 1,2
spark.read.csv('testfile.csv').collect()
# [Row(_c0='"a 2.5"" drive"', _c1='another column'),
# Row(_c0='"a ""quoted"" string"', _c1='"""quoted"""'),
# Row(_c0='1', _c1='2')]
# explicitly stating the escape character fixed the issue
spark.read.option('escape', '"').csv('testfile.csv').collect()
# [Row(_c0='a 2.5" drive', _c1='another column'),
# Row(_c0='a "quoted" string', _c1='"quoted"'),
# Row(_c0='1', _c1='2')]
{code}
The same applies to writes, where reading the file written by Spark may result
in garbage.
{code}
df = spark.read.option('escape', '"').csv('testfile.csv') # reading the file
correctly
df.write.format("csv").save('testout.csv')
with open('testout.csv/part-....csv') as f:
cr = csv.reader(f)
print(next(cr))
print(next(cr))
# ['a 2.5\\ drive"', 'another column']
# ['a \\quoted\\" string"', '\\quoted\\""']
{code}
While it's possible to work with CSV files in a "compatible" manner, it would
be useful if Spark had sensible defaults that conform to the above-mentioned
RFC (as well as W3C recommendations). I realise this would be a breaking change
and thus if accepted, it would probably need to result in a warning first,
before moving to a new default.
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