如何将整列的大小写改为小写？

Question

我想在Spark数据集中将整列的大小写更改为小写

        Desired Input
        +------+--------------------+
        |ItemID|       Category name|
        +------+--------------------+
        |   ABC|BRUSH & BROOM HAN...|
        |   XYZ|WHEEL BRUSH PARTS...|
        +------+--------------------+

        Desired Output
        +------+--------------------+
        |ItemID|       Category name|
        +------+--------------------+
        |   ABC|brush & broom han...|
        |   XYZ|wheel brush parts...|
        +------+--------------------+

我尝试使用collectAsList()和toString(),这对于非常大的数据集来说是一个缓慢而复杂的过程.

我还发现了一种方法'较低',但没有知道如何让它在dasaset中工作请建议我一个简单或有效的方法来做到这一点.提前致谢

Answer 1

我知道了

        String columnName="Category name";
        src=src.withColumn(columnName, lower(col(columnName)));
        src.show();

这取代了旧的列,新的列保留了整个数据集.

        +------+--------------------+
        |ItemID|       Category name|
        +------+--------------------+
        |   ABC|brush & broom han...|
        |   XYZ|wheel brush parts...|
        +------+--------------------+

Answer 2

使用lower功能org.apache.spark.sql.functions

例如:

df.select($"q1Content", lower($"q1Content")).show

输出.

+--------------------+--------------------+
|           q1Content|    lower(q1Content)|
+--------------------+--------------------+
|What is the step ...|what is the step ...|
|What is the story...|what is the story...|
|How can I increas...|how can i increas...|
|Why am I mentally...|why am i mentally...|
|Which one dissolv...|which one dissolv...|
|Astrology: I am a...|astrology: i am a...|
| Should I buy tiago?| should i buy tiago?|
|How can I be a go...|how can i be a go...|
|When do you use  ...|when do you use  ...|
|Motorola (company...|motorola (company...|
|Method to find se...|method to find se...|
|How do I read and...|how do i read and...|
|What can make Phy...|what can make phy...|
|What was your fir...|what was your fir...|
|What are the laws...|what are the laws...|
|What would a Trum...|what would a trum...|
|What does manipul...|what does manipul...|
|Why do girls want...|why do girls want...|
|Why are so many Q...|why are so many q...|
|Which is the best...|which is the best...|
+--------------------+--------------------+