[GitHub] spark pull request #20959: [SPARK-23846][SQL] The samplingRatio option for C...

[HyukjinKwon]

Github user HyukjinKwon commented on a diff in the pull request:

    https://github.com/apache/spark/pull/20959#discussion_r182607885
  
    --- Diff: 
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/csv/CSVDataSource.scala
 ---
    @@ -161,7 +161,8 @@ object TextInputCSVDataSource extends CSVDataSource {
           val firstRow = new 
CsvParser(parsedOptions.asParserSettings).parseLine(firstLine)
           val caseSensitive = 
sparkSession.sessionState.conf.caseSensitiveAnalysis
           val header = makeSafeHeader(firstRow, caseSensitive, parsedOptions)
    -      val tokenRDD = csv.rdd.mapPartitions { iter =>
    +      val sampled: Dataset[String] = CSVUtils.sample(csv, parsedOptions)
    +      val tokenRDD = sampled.rdd.mapPartitions { iter =>
    --- End diff --
    
    ```
    $ tree .
    .
    ├── a.json
    ├── b.json
    ├── c.json
    ├── d.json
    ├── e.json
    ├── f.json
    └── h.json
    
    0 directories, 7 files
    ```
    
    ```
    $ cat *
    {"a": "a"}
    {"a": 1}
    
    {"a": 1}
    
    {"a": 1}
    
    {"a": 1}
    
    {"a": 1}
    
    {"a": 1}
    ```
    
    ```scala
    scala> spark.read.option("samplingRatio", 0.1).json("tmp").schema
    res0: org.apache.spark.sql.types.StructType = 
StructType(StructField(a,LongType,true))
    
    scala> spark.read.option("samplingRatio", 1).json("tmp").schema
    res1: org.apache.spark.sql.types.StructType = 
StructType(StructField(a,StringType,true))
    ```



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