+dev for more visibility. Is this a known issue? Is there a plan for a fix?
Thanks,
David
> Begin forwarded message:
>
> From: Dávid Szakállas <david.szakal...@gmail.com>
> Subject: Dataset schema incompatibility bug when reading column partitioned
> data
> Date: 2019. March 29. 14:15:27 CET
> To: u...@spark.apache.org
>
> We observed the following bug on Spark 2.4.0:
>
> scala>
> spark.createDataset(Seq((1,2))).write.partitionBy("_1").parquet("foo.parquet")
>
> scala> val schema = StructType(Seq(StructField("_1",
> IntegerType),StructField("_2", IntegerType)))
>
> scala> spark.read.schema(schema).parquet("foo.parquet").as[(Int, Int)].show
> +---+---+
> | _2| _1|
> +---+---+
> | 2| 1|
> +---+- --+
>
> That is, when reading column partitioned Parquet files the explicitly
> specified schema is not adhered to, instead the partitioning columns are
> appended the end of the column list. This is a quite severe issue as some
> operations, such as union, fails if columns are in a different order in two
> datasets. Thus we have to work around the issue with a select:
>
> val columnNames = schema.fields.map(_.name)
> ds.select(columnNames.head, columnNames.tail: _*)
>
>
> Thanks,
> David Szakallas
> Data Engineer | Whitepages, Inc.
