如何将整列的大小写更改为小写？

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...|
        +------+--------------------+

我尝试了 collectAsList() 和 toString()，这对于非常大的数据集来说是缓慢而复杂的过程。

我也找到了一种方法 'lower' 但不知道如何在 dasaset 中使用它请给我一个简单或有效的方法来完成上述操作。提前致谢

Answer 1

使用 org.apache.spark.sql.functions

中的 lower 函数

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...|
+--------------------+--------------------+

Answer 2

我知道了（使用 Functions#lower，参见 Javadoc）

import org.apache.spark.sql.functions.lower

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

这用保留整个数据集的新列替换了旧列。

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

Answer 3

首先你应该通过

添加库

import static org.apache.spark.sql.functions.lower;

那么您需要将 lower 方法放在正确的位置。这是一个例子：

.and(lower(df1.col("field_name")).equalTo("offeringname"))

我已经阅读了这里的所有答案，然后自己尝试了，出于某种原因，我在 IntelliJ Idea 上停留了几分钟，直到我能理解它（图书馆方面）。如果您遇到这个问题，只需按照 IntelliJ 的建议添加库，因为它会在未知时弹出。

祝你好运。

Answer 4

你可以在 Scala 中这样做：

import org.apache.spark.sql.functions._

val dfAfterLowerCase = dfInitial.withColumn("column_name", lower(col("column_name")))
dfAfterLowerCase.show()

如何将整列的大小写更改为小写？

How to change case of whole column to lowercase?

java

apache-spark

apache-spark-sql

apache-spark-dataset