[GitHub] [spark] liancheng edited a comment on issue #25382: [SPARK-28651][SS]Force streaming file source to be nullable

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liancheng edited a comment on issue #25382: [SPARK-28651][SS]Force streaming file source to be nullable
URL: https://github.com/apache/spark/pull/25382#issuecomment-519645724
 
 
   Unfortunately, I didn't add a comprehensive PR description or comments in the original PR to explain why we wanted a nullable schema (I guess we were rushing the 1.4 release back then)...
   
   From what I could recall, possible motivations could be due to Hive compatibility and Parquet interoperability. Hive metastore doesn't respect nullability and always have nullable columns. Parquet interoperability was in trouble in 1.4 due to ambiguity in the parquet-format spec and different systems were using different schemas when writing nested columns, and forcing the schema nullable could help in resolving part of the cases (esp. for Hive). But Spark Parquet interoperability is no longer an issue since 1.6.

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