hadoop - How to export data from Spark SQL to CSV

Question

This command works with HiveQL:

insert overwrite directory '/data/home.csv' select * from testtable;

But with Spark SQL I'm getting an error with an org.apache.spark.sql.hive.HiveQl stack trace:

java.lang.RuntimeException: Unsupported language features in query:
    insert overwrite directory '/data/home.csv' select * from testtable

Please guide me to write export to CSV feature in Spark SQL.

Answer 1

You can use below statement to write the contents of dataframe in CSV format df.write.csv("/data/home/csv")

If you need to write the whole dataframe into a single CSV file, then use df.coalesce(1).write.csv("/data/home/sample.csv")

For spark 1.x, you can use spark-csv to write the results into CSV files

Below scala snippet would help

import org.apache.spark.sql.hive.HiveContext
// sc - existing spark context
val sqlContext = new HiveContext(sc)
val df = sqlContext.sql("SELECT * FROM testtable")
df.write.format("com.databricks.spark.csv").save("/data/home/csv")

To write the contents into a single file

import org.apache.spark.sql.hive.HiveContext
// sc - existing spark context
val sqlContext = new HiveContext(sc)
val df = sqlContext.sql("SELECT * FROM testtable")
df.coalesce(1).write.format("com.databricks.spark.csv").save("/data/home/sample.csv")