scala> schemaTyped("a").getComment
res0: Option[String] = None
scala> schemaTyped("a").withComment("this is a comment").getComment
res1: Option[String] = Some(this is a comment)StructField — Single Field in StructType
StructField describes a single field in a StructType with the following:
A comment is part of metadata under comment key and is used to build a Hive column or when describing a table.
As of Spark 2.4.0, StructField can be converted to DDL format using toDDL method.
Example: Using StructField.toDDL
import org.apache.spark.sql.types.MetadataBuilder
val metadata = new MetadataBuilder()
.putString("comment", "this is a comment")
.build
import org.apache.spark.sql.types.{LongType, StructField}
val f = new StructField(name = "id", dataType = LongType, nullable = false, metadata)
scala> println(f.toDDL)
`id` BIGINT COMMENT 'this is a comment' Converting to DDL Format — toDDL Method
toDDL: StringtoDDL gives a text in the format:
[quoted name] [dataType][optional comment]|
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