文本文件
Spark SQL 提供了 spark.read().text("file_name")
来将文本文件或文本文件目录读取到 Spark DataFrame 中,以及 dataframe.write().text("path")
来写入到文本文件。当读取文本文件时,默认情况下,每行都会成为具有字符串 "value" 列的行。行分隔符可以更改,如下面的示例所示。可以使用 option()
函数来自定义读取或写入的行为,例如控制行分隔符、压缩等行为。
# spark is from the previous example
sc = spark.sparkContext
# A text dataset is pointed to by path.
# The path can be either a single text file or a directory of text files
path = "examples/src/main/resources/people.txt"
df1 = spark.read.text(path)
df1.show()
# +-----------+
# | value|
# +-----------+
# |Michael, 29|
# | Andy, 30|
# | Justin, 19|
# +-----------+
# You can use 'lineSep' option to define the line separator.
# The line separator handles all `\r`, `\r\n` and `\n` by default.
df2 = spark.read.text(path, lineSep=",")
df2.show()
# +-----------+
# | value|
# +-----------+
# | Michael|
# | 29\nAndy|
# | 30\nJustin|
# | 19\n|
# +-----------+
# You can also use 'wholetext' option to read each input file as a single row.
df3 = spark.read.text(path, wholetext=True)
df3.show()
# +--------------------+
# | value|
# +--------------------+
# |Michael, 29\nAndy...|
# +--------------------+
# "output" is a folder which contains multiple text files and a _SUCCESS file.
df1.write.csv("output")
# You can specify the compression format using the 'compression' option.
df1.write.text("output_compressed", compression="gzip")
在 Spark 仓库的 "examples/src/main/python/sql/datasource.py" 中查找完整的示例代码。
// A text dataset is pointed to by path.
// The path can be either a single text file or a directory of text files
val path = "examples/src/main/resources/people.txt"
val df1 = spark.read.text(path)
df1.show()
// +-----------+
// | value|
// +-----------+
// |Michael, 29|
// | Andy, 30|
// | Justin, 19|
// +-----------+
// You can use 'lineSep' option to define the line separator.
// The line separator handles all `\r`, `\r\n` and `\n` by default.
val df2 = spark.read.option("lineSep", ",").text(path)
df2.show()
// +-----------+
// | value|
// +-----------+
// | Michael|
// | 29\nAndy|
// | 30\nJustin|
// | 19\n|
// +-----------+
// You can also use 'wholetext' option to read each input file as a single row.
val df3 = spark.read.option("wholetext", true).text(path)
df3.show()
// +--------------------+
// | value|
// +--------------------+
// |Michael, 29\nAndy...|
// +--------------------+
// "output" is a folder which contains multiple text files and a _SUCCESS file.
df1.write.text("output")
// You can specify the compression format using the 'compression' option.
df1.write.option("compression", "gzip").text("output_compressed")
在 Spark 仓库的 "examples/src/main/scala/org/apache/spark/examples/sql/SQLDataSourceExample.scala" 中查找完整的示例代码。
import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;
// A text dataset is pointed to by path.
// The path can be either a single text file or a directory of text files
String path = "examples/src/main/resources/people.txt";
Dataset<Row> df1 = spark.read().text(path);
df1.show();
// +-----------+
// | value|
// +-----------+
// |Michael, 29|
// | Andy, 30|
// | Justin, 19|
// +-----------+
// You can use 'lineSep' option to define the line separator.
// The line separator handles all `\r`, `\r\n` and `\n` by default.
Dataset<Row> df2 = spark.read().option("lineSep", ",").text(path);
df2.show();
// +-----------+
// | value|
// +-----------+
// | Michael|
// | 29\nAndy|
// | 30\nJustin|
// | 19\n|
// +-----------+
// You can also use 'wholetext' option to read each input file as a single row.
Dataset<Row> df3 = spark.read().option("wholetext", "true").text(path);
df3.show();
// +--------------------+
// | value|
// +--------------------+
// |Michael, 29\nAndy...|
// +--------------------+
// "output" is a folder which contains multiple text files and a _SUCCESS file.
df1.write().text("output");
// You can specify the compression format using the 'compression' option.
df1.write().option("compression", "gzip").text("output_compressed");
在 Spark 仓库的 "examples/src/main/java/org/apache/spark/examples/sql/JavaSQLDataSourceExample.java" 中查找完整的示例代码。
数据源选项
文本数据源选项可以通过以下方式设置
.option
/.options
方法DataFrameReader
DataFrameWriter
DataStreamReader
DataStreamWriter
OPTIONS
子句位于 CREATE TABLE USING DATA_SOURCE
属性名称 | 默认值 | 含义 | 范围 |
---|---|---|---|
wholetext |
false |
如果为 true,则将输入路径中的每个文件读取为单行。 | 读 |
lineSep |
\r , \r\n , \n (用于读取),\n (用于写入) |
定义应该用于读取或写入的行分隔符。 | 读/写 |
compression |
(无) | 保存到文件时使用的压缩编解码器。可以是已知的不区分大小写的缩写名称之一 (none, bzip2, gzip, lz4, snappy 和 deflate)。 | 写 |
其他通用选项可以在 通用文件源选项 中找到。