Harry Brundage created SPARK-1849:
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Summary: Broken UTF-8 encoded data gets character replacements and
thus can't be "fixed"
Key: SPARK-1849
URL: https://issues.apache.org/jira/browse/SPARK-1849
Project: Spark
Issue Type: Bug
Reporter: Harry Brundage
Fix For: 1.0.0, 0.9.1
Attachments: encoding_test
I'm trying to process a file which isn't valid UTF-8 data inside hadoop using
Spark via {{sc.textFile()}}. Is this possible, and if not, is this a bug that
we should fix? It looks like {{HadoopRDD}} uses
{{org.apache.hadoop.io.Text.toString}} on all the data it ever reads, which I
believe replaces invalid UTF-8 byte sequences with the UTF-8 replacement
character, \uFFFD. Some example code mimicking what {{sc.textFile}} does
underneath:
{code}
scala> sc.textFile(path).collect()(0)
res8: String = ?pple
scala> sc.hadoopFile(path, classOf[TextInputFormat], classOf[LongWritable],
classOf[Text]).map(pair => pair._2.toString).collect()(0).getBytes()
res9: Array[Byte] = Array(-17, -65, -67, 112, 112, 108, 101)
scala> sc.hadoopFile(path, classOf[TextInputFormat], classOf[LongWritable],
classOf[Text]).map(pair => pair._2.getBytes).collect()(0)
res10: Array[Byte] = Array(-60, 112, 112, 108, 101)
{code}
In the above example, the first two snippets show the string representation and
byte representation of the example line of text. The third snippet shows what
happens if you call {{getBytes}} on the {{Text}} object which comes back from
hadoop land: we get the real bytes in the file out.
Now, I think this is a bug, though you may disagree. The text inside my file is
perfectly valid iso-8859-1 encoded bytes, which I would like to be able to
rescue and re-encode into UTF-8, because I want my application to be smart like
that. I think Spark should give me the raw broken string so I can re-encode,
but I can't get at the original bytes in order to guess at what the source
encoding might be, as they have already been replaced. I'm dealing with data
from some CDN access logs which are to put it nicely diversely encoded, but I
think a use case Spark should fully support. So, my suggested fix, which I'd
like some guidance, is to change {{textFile}} to spit out broken strings by not
using {{Text}}'s UTF-8 encoding.
Further compounding this issue is that my application is actually in PySpark,
but we can talk about how bytes fly through to Scala land after this if we
agree that this is an issue at all.
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