[
https://issues.apache.org/jira/browse/SPARK-19488?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Wenchen Fan resolved SPARK-19488.
---------------------------------
Resolution: Fixed
Fix Version/s: 2.2.0
Issue resolved by pull request 16834
[https://github.com/apache/spark/pull/16834]
> CSV infer schema does not take into account Inf,-Inf,NaN
> --------------------------------------------------------
>
> Key: SPARK-19488
> URL: https://issues.apache.org/jira/browse/SPARK-19488
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 2.0.2
> Environment: Windows 10, SparkShell
> Reporter: Shivam Dalmia
> Assignee: Song Jun
> Labels: easyfix, features
> Fix For: 2.2.0
>
>
> I observed that while loading a CSV as a dataframe, user-specified values for
> nanValue, positiveInf and negativeInf are disregarded when inferSchema =
> true. (They work if a user-specified schema is provided). However, even the
> spark defaults for the infinities (Inf and -Inf) do not work with
> inferSchema.
> Taking a look at the source code for the inferSchema for CSV
> (CSVInferSchema.scala), I found the following code snippet.
> {code}
> 1. private def tryParseDouble(field: String, options: CSVOptions):
> DataType = {
> 2. if ((allCatch opt field.toDouble).isDefined) {
> 3. DoubleType
> 4. } else {
> 5. tryParseTimestamp(field, options)
> 6. }
> 7. }
> 8.
> 9. private def tryParseTimestamp(field: String, options:
> CSVOptions): DataType = {
> 10. // This case infers a custom `dataFormat` is set.
> 11. if ((allCatch opt
> options.timestampFormat.parse(field)).isDefined) {
> 12. TimestampType
> 13. } else if ((allCatch opt
> DateTimeUtils.stringToTime(field)).isDefined) {
> 14. // We keep this for backwords competibility.
> 15. TimestampType
> 16. } else {
> 17. tryParseBoolean(field, options)
> 18. }
> 19. }
> {code}
> Interestingly, the user-specified csv options are not at all used while
> determining if the field is of type double (as we can see in line 2). We can
> see that the options is used for timestamp type (line 11), which is why the
> 'dateFormat' option does work.
> However, when the field is NaN, it works because scala's toDouble function
> does convert the string NaN to the double equivalent of NaN. (I tried it
> using the shell):
> {code}
> scala> allCatch.opt(field.toDouble)
> res12: Option[Double] = Some(8.0942)
> scala> var field = "NaN";
> field: String = NaN
> scala> allCatch.opt(field.toDouble)
> res13: Option[Double] = Some(NaN)
> scala> var field = "Inf";
> field: String = Inf
> scala> allCatch.opt(field.toDouble)
> res14: Option[Double] = None
> {code}
> Interestingly, scala does have Double equivalents of Infinity and -Infinity
> (but spark defaults are Inf and -Inf, which is why they don't work):
> {code}
> scala> field = "Infinity";
> field: String = Infinity
> scala> allCatch.opt(field.toDouble)
> res15: Option[Double] = Some(Infinity)
> scala> field = "-Infinity";
> field: String = -Infinity
> scala> allCatch.opt(field.toDouble)
> res16: Option[Double] = Some(-Infinity)
> {code}
> The following csv, when ingested with inferSchema = true, therefore
> interprets the value column as a Double! (Regardless of the user-specified
> options)
> {code}
> ID,name,value,irrational,prime,real
> 1,e,2.7,true,false,true
> 2,pi,3.14,true,false,true
> 3,inf,Infinity,false,false,true
> 4,-inf,-Infinity,false,false,true
> 5,i,NaN,false,false,false
> {code}
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