GitHub user gatorsmile opened a pull request:
https://github.com/apache/spark/pull/13770
[SPARK-16054] [SQL] Verification of DataFrameReader API Usage
#### What changes were proposed in this pull request?
Below are **potential user errors** when using DataFrameReader APIs
- Specify format when reading tables from catalog.
```scala
spark.read.format("parquet").table(tableName)
```
- Specify schema when reading tables from catalog
```scala
val schema = StructType(StructField("c1", IntegerType) :: Nil)
spark.read.schema(schema).table(tableName)
```
- Specify options when reading tables from catalog
```scala
spark.read.options(Map("header" -> "true", "mode" ->
"dropmalformed")).table(tableName)
```
- Specify the format more than once
```scala
val format = "parquet"
spark.read.format(format).json(path.getCanonicalPath)
```
- Specify schema more than once.
```scala
spark.read.schema(schema1).schema(schema2).json(path.getCanonicalPath)
```
This PR detects these user errors and issues the exception.
#### How was this patch tested?
Test cases are added to `DataFrameReaderWriterSuite`
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/gatorsmile/spark dataframeReaderTable
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/13770.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 #13770
----
commit bce14a161e0248ef0a5e2170f0d1d0c930f3b5dd
Author: gatorsmile <[email protected]>
Date: 2016-06-19T07:10:30Z
fix
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