[jira] [Closed] (SPARK-20593) Writing Parquet: Cannot build an empty group

["Herman van Hovell (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-20593?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Herman van Hovell closed SPARK-20593.
-------------------------------------
    Resolution: Not A Problem

> Writing Parquet: Cannot build an empty group
> --------------------------------------------
>
>                 Key: SPARK-20593
>                 URL: https://issues.apache.org/jira/browse/SPARK-20593
>             Project: Spark
>          Issue Type: Question
>          Components: Spark Core, Spark Shell
>    Affects Versions: 2.1.1
>         Environment: I use Apache Spark 2.1.1 (used 2.1.0 and it was the same, switched today). Tested only on Mac
>            Reporter: Viktor Khristenko
>            Priority: Minor
>
> Hi,
> This is my first ticket and I apologize for/if I'm doing certain things in an improper way.
>  I have a dataset:
> {noformat}
> root
> |-- muons: array (nullable = true)
> |    |-- element: struct (containsNull = true)
> |    |    |-- reco::Candidate: struct (nullable = true)
> |    |    |-- qx3_: integer (nullable = true)
> |    |    |-- pt_: float (nullable = true)
> |    |    |-- eta_: float (nullable = true)
> |    |    |-- phi_: float (nullable = true)
> |    |    |-- mass_: float (nullable = true)
> |    |    |-- vertex_: struct (nullable = true)
> |    |    |    |-- fCoordinates: struct (nullable = true)
> |    |    |    |    |-- fX: float (nullable = true)
> |    |    |    |    |-- fY: float (nullable = true)
> |    |    |    |    |-- fZ: float (nullable = true)
> |    |    |-- pdgId_: integer (nullable = true)
> |    |    |-- status_: integer (nullable = true)
> |    |    |-- cachePolarFixed_: struct (nullable = true)
> |    |    |-- cacheCartesianFixed_: struct (nullable = true)
> {noformat}
> As you can see, there are 3 empty structs in this schema. I know 100% that I can read/manipulate/do whatever. However, when I try writing to disk in parquet, I get the following Exception:
> ds.write.format("parquet").save(outputPathName):
> java.lang.IllegalStateException: Cannot build an empty group
> at org.apache.parquet.Preconditions.checkState(Preconditions.java:91)
> at org.apache.parquet.schema.Types$BaseGroupBuilder.build(Types.java:622)
> at org.apache.parquet.schema.Types$BaseGroupBuilder.build(Types.java:497)
> at org.apache.parquet.schema.Types$Builder.named(Types.java:286)
> at org.apache.spark.sql.execution.datasources.parquet.ParquetSchemaConverter.convertField(ParquetSchemaConverter.scala:535)
> at org.apache.spark.sql.execution.datasources.parquet.ParquetSchemaConverter.convertField(ParquetSchemaConverter.scala:321)
> at org.apache.spark.sql.execution.datasources.parquet.ParquetSchemaConverter$$anonfun$convertField$1.apply(ParquetSchemaConverter.scala:534)
> at org.apache.spark.sql.execution.datasources.parquet.ParquetSchemaConverter$$anonfun$convertField$1.apply(ParquetSchemaConverter.scala:533)
> So, basically I would like to understand if it's a bug or an intended behavior??? I also assume that it's related to the empty structs. Any help would be really appreciated!
> I've quickly created stripped version and that one works without any issues!
> For reference, I put a link to the original question on SO[1]
> VK
> [1] http://stackoverflow.com/questions/43767358/apache-spark-parquet-cannot-build-an-empty-group



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