GitHub user sameeragarwal opened a pull request:
https://github.com/apache/spark/pull/17847
[SPARK-20590] Map default input data source formats to inlined classes
## What changes were proposed in this pull request?
One of the common usability problems around reading data in spark
(particularly CSV) is that there can often be a conflict between different
readers in the classpath.
As an example, if someone launches a 2.x spark shell with the spark-csv
package in the classpath, Spark currently fails in an extremely unfriendly way
(see https://github.com/databricks/spark-csv/issues/367):
```scala
./bin/spark-shell --packages com.databricks:spark-csv_2.11:1.5.0
scala> val df = spark.read.csv("/foo/bar.csv")
java.lang.RuntimeException: Multiple sources found for csv
(org.apache.spark.sql.execution.datasources.csv.CSVFileFormat,
com.databricks.spark.csv.DefaultSource15), please specify the fully qualified
class name.
at scala.sys.package$.error(package.scala:27)
at
org.apache.spark.sql.execution.datasources.DataSource$.lookupDataSource(DataSource.scala:574)
at
org.apache.spark.sql.execution.datasources.DataSource.providingClass$lzycompute(DataSource.scala:85)
at
org.apache.spark.sql.execution.datasources.DataSource.providingClass(DataSource.scala:85)
at
org.apache.spark.sql.execution.datasources.DataSource.resolveRelation(DataSource.scala:295)
at org.apache.spark.sql.DataFrameReader.load(DataFrameReader.scala:178)
at org.apache.spark.sql.DataFrameReader.csv(DataFrameReader.scala:533)
at org.apache.spark.sql.DataFrameReader.csv(DataFrameReader.scala:412)
... 48 elided
```
This patch proposes a simple way of fixing this error by always mapping
default input data source formats to inlined classes (that exist in Spark):
```scala
./bin/spark-shell --packages com.databricks:spark-csv_2.11:1.5.0
scala> val df = spark.read.csv("/foo/bar.csv")
df: org.apache.spark.sql.DataFrame = [_c0: string]
```
## How was this patch tested?
Existing Tests
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/sameeragarwal/spark csv-fix
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/17847.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #17847
----
commit 1af4675707a6fe1a1acaff0a30e8ef6c2ed5ff46
Author: Sameer Agarwal <[email protected]>
Date: 2017-05-03T20:57:16Z
map short names to correct class
----
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