mingkangli-db opened a new pull request, #42463:
URL: https://github.com/apache/spark/pull/42463
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### What changes were proposed in this pull request?
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This PR changes the logic of SchemaConverter.scala of the Avro connector
when it deals with unions of a single type.
In the existing implementation, there seems to be an inconsistency in how
the Spark-Avro connector converts Avro schemas to Spark's StructType. For
complex union types, the conversion seems to work fine, wrapping the type into
a StructType. However, for primitive union types (like ["null", "string"]), the
connector simply returns the primitive type (in this case, StringType) without
wrapping it into a StructType. This behavior may result in an exception if we
are expecting a StructType but encounter a primitive type instead, and some
users might want a more consistent conversion behavior.
For instance, for a type union["string", null], it now converts it to a
StructType(StringType) in Spark instead of a StringType.
Note: this PR is **not to be merged** as it alters the default behavior. A
more appropriate method is to add a config and adopt the changes only if that
config flag is on.
### Why are the changes needed?
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### Does this PR introduce _any_ user-facing change?
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