[GitHub] gengliangwang opened a new pull request #23824: [SPARK-26913][SQL] New data source V2 API: SupportsDirectWrite

[GitBox <gi...@apache.org>]

gengliangwang opened a new pull request #23824: [SPARK-26913][SQL] New data source V2 API: SupportsDirectWrite
URL: https://github.com/apache/spark/pull/23824
 
 
   ## What changes were proposed in this pull request?
   
   Spark supports writing to file data sources without getting the table schema and validation with the schema.
   For example, 
   ```
   spark.range(10).write.orc(path)
   val newDF = spark.range(20).map(id => (id.toDouble, id.toString)).toDF("double", "string")
   newDF.write.mode("overwrite").orc(path)
   ```
   1. There is no actions to get/infer the schema from the table/path
   2. The schema of `newDF` can be different with the original table schema.
   
   However, from https://github.com/apache/spark/pull/23606/files#r255319992 we can see that **the feature above is still missing in data source V2**. Currently, data source V2 always validates the output query with the table schema. Even after the catalog support of DS V2 is implemented, I think it is hard to support both behaviors with the current API/framework.
   
   This PR proposes to create a new mix-in interface `SupportsDirectWrite`. With the interface, Spark will write to the table location directly without schema inference and validation on `DataFrameWriter.save()`.
   
   The PR also reeanbles Orc data source V2.
   
   ## How was this patch tested?
   
   Unit test
   

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