spark-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Anastasios Zouzias <zouz...@gmail.com>
Subject Re: Error - Spark reading from HDFS via dataframes - Java
Date Sun, 01 Oct 2017 07:04:55 GMT
Hi,

Set the inferschema option to true in spark-csv. you may also want to set
the mode option. See readme below

https://github.com/databricks/spark-csv/blob/master/README.md

Best,
Anastasios

Am 01.10.2017 07:58 schrieb "Kanagha Kumar" <kprasad@salesforce.com>:

Hi,

I'm trying to read data from HDFS in spark as dataframes. Printing the
schema, I see all columns are being read as strings. I'm converting it to
RDDs and creating another dataframe by passing in the correct schema ( how
the rows should be interpreted finally).

I'm getting the following error:

Caused by: java.lang.RuntimeException: java.lang.String is not a valid
external type for schema of bigint



Spark read API:

Dataset<Row> hdfs_dataset = new SQLContext(spark).read().option("header",
"false").csv("hdfs:/inputpath/*");

Dataset<Row> ds = new
SQLContext(spark).createDataFrame(hdfs_dataset.toJavaRDD(),
conversionSchema);
This is the schema to be converted to:
StructType(StructField(COL1,StringType,true),
StructField(COL2,StringType,true),
StructField(COL3,LongType,true),
StructField(COL4,StringType,true),
StructField(COL5,StringType,true),
StructField(COL6,LongType,true))

This is the original schema obtained once read API was invoked
StructType(StructField(_c1,StringType,true),
StructField(_c2,StringType,true),
StructField(_c3,StringType,true),
StructField(_c4,StringType,true),
StructField(_c5,StringType,true),
StructField(_c6,StringType,true))

My interpretation is even when a JavaRDD is cast to dataframe by passing in
the new schema, values are not getting type casted.
This is occurring because the above read API reads data as string types
from HDFS.

How can I  convert an RDD to dataframe by passing in the correct schema
once it is read?
How can the values by type cast correctly during this RDD to dataframe
conversion?

Or how can I read data from HDFS with an input schema in java?
Any suggestions are helpful. Thanks!

Mime
View raw message