Spark DataFrame 和重命名多列（Java）
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Spark DataFrame and renaming multiple columns (Java)
提问by JiriS
Is there any nicer way to prefix or rename all or multiple columns at the same time of a given SparkSQL DataFramethan calling multiple times dataFrame.withColumnRenamed()?
有没有DataFrame比多次调用更好的方法来为给定 SparkSQL 的所有或多个列同时添加前缀或重命名dataFrame.withColumnRenamed()？
An example would be if I want to detect changes (using full outer join). Then I'm left with two DataFrames with the same structure.
一个例子是，如果我想检测更改（使用完全外连接）。然后我剩下两个DataFrame具有相同结构的 s。
采纳答案by Zyoma
I suggest to use the select() method to perform this. In fact withColumnRenamed() method uses select() by itself. Here is example how to rename multiple columns:
我建议使用 select() 方法来执行此操作。实际上 withColumnRenamed() 方法本身使用 select() 。以下是如何重命名多列的示例：
import org.apache.spark.sql.functions._
val someDataframe: DataFrame = ...
val initialColumnNames = Seq("a", "b", "c")
val renamedColumns = initialColumnNames.map(name => col(name).as(s"renamed_$name"))
someDataframe.select(renamedColumns : _*)
回答by lanenok
I heve just found the answer
我刚刚找到了答案
df1_r = df1.select(*(col(x).alias(x + '_df1') for x in df1.columns))
at stackoverflow here(see the end of the accepted answer)
在此处的stackoverflow（请参阅已接受答案的结尾）
回答by Devndra
or (a <- 0 to newsales.columns.length - 1)
{
var new_c = newsales.columns(a).replace('(','_').replace(')',' ').trim
newsales_var = newsales.withColumnRenamed(newsales.columns(a),new_c)
}
回答by Alsace
I think this method can help you.
我觉得这个方法可以帮到你。
public static Dataset<Row> renameDataFrame(Dataset<Row> dataset) {
for (String column : dataset.columns()) {
dataset = dataset.withColumnRenamed(column, SystemUtils.underscoreToCamelCase(column));
}
return dataset;
}
public static String underscoreToCamelCase(String underscoreName) {
StringBuilder result = new StringBuilder();
if (underscoreName != null && underscoreName.length() > 0) {
boolean flag = false;
for (int i = 0; i < underscoreName.length(); i++) {
char ch = underscoreName.charAt(i);
if ("_".charAt(0) == ch) {
flag = true;
} else {
if (flag) {
result.append(Character.toUpperCase(ch));
flag = false;
} else {
result.append(ch);
}
}
}
}
return result.toString();
}
