How to write dataframe (obtained from hive table) into hadoop SequenceFile and RCFile?

问题

I am able to write it into

• ORC

• PARQUET

  directly and

• TEXTFILE

• AVRO

using additional dependencies from databricks.

    <dependency>
        <groupId>com.databricks</groupId>
        <artifactId>spark-csv_2.10</artifactId>
        <version>1.5.0</version>
    </dependency>
    <dependency>
        <groupId>com.databricks</groupId>
        <artifactId>spark-avro_2.10</artifactId>
        <version>2.0.1</version>
    </dependency>

Sample code:

    SparkContext sc = new SparkContext(conf);
    HiveContext hc = new HiveContext(sc);
    DataFrame df = hc.table(hiveTableName);
    df.printSchema();
    DataFrameWriter writer = df.repartition(1).write();

    if ("ORC".equalsIgnoreCase(hdfsFileFormat)) {
        writer.orc(outputHdfsFile);

    } else if ("PARQUET".equalsIgnoreCase(hdfsFileFormat)) {
        writer.parquet(outputHdfsFile);

    } else if ("TEXTFILE".equalsIgnoreCase(hdfsFileFormat)) {
        writer.format("com.databricks.spark.csv").option("header", "true").save(outputHdfsFile);

    } else if ("AVRO".equalsIgnoreCase(hdfsFileFormat)) {
        writer.format("com.databricks.spark.avro").save(outputHdfsFile);
    }

Is there any way to write dataframe into hadoop SequenceFile and RCFile?

回答1:

You can use void saveAsObjectFile(String path) to save a RDD as a SequenceFile of serialized objects. So in your case you have to to retrieve the RDD from the DataFrame:

JavaRDD<Row> rdd = df.javaRDD;
rdd.saveAsObjectFile(outputHdfsFile);

来源：https://stackoverflow.com/questions/39830518/how-to-write-dataframe-obtained-from-hive-table-into-hadoop-sequencefile-and-r