Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/3925#discussion_r22631880
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/types/dataTypes.scala ---
@@ -510,19 +671,92 @@ case class StructField(
}
}
+
object StructType {
protected[sql] def fromAttributes(attributes: Seq[Attribute]):
StructType =
StructType(attributes.map(a => StructField(a.name, a.dataType,
a.nullable, a.metadata)))
+
+ def apply(fields: Seq[StructField]): StructType =
StructType(fields.toArray)
+
+ def apply(fields: java.util.List[StructField]): StructType = {
+ StructType(fields.toArray.asInstanceOf[Array[StructField]])
+ }
}
-case class StructType(fields: Seq[StructField]) extends DataType {
- /**
- * Returns all field names in a [[Seq]].
- */
- lazy val fieldNames: Seq[String] = fields.map(_.name)
+/**
+ * :: DeveloperApi ::
+ *
+ * A [[StructType]] object can be constructed by
+ * {{{
+ * StructType(fields: Seq[StructField])
+ * }}}
+ * For a [[StructType]] object, one or multiple [[StructField]]s can be
extracted by names.
+ * If multiple [[StructField]]s are extracted, a [[StructType]] object
will be returned.
+ * If a provided name does not have a matching field, it will be ignored.
For the case
+ * of extracting a single StructField, a `null` will be returned.
+ * Example:
+ * {{{
+ * import org.apache.spark.sql._
+ *
+ * val struct =
+ * StructType(
+ * StructField("a", IntegerType, true) ::
+ * StructField("b", LongType, false) ::
+ * StructField("c", BooleanType, false) :: Nil)
+ *
+ * // Extract a single StructField.
+ * val singleField = struct("b")
+ * // singleField: StructField = StructField(b,LongType,false)
+ *
+ * // This struct does not have a field called "d". null will be returned.
+ * val nonExisting = struct("d")
+ * // nonExisting: StructField = null
+ *
+ * // Extract multiple StructFields. Field names are provided in a set.
+ * // A StructType object will be returned.
--- End diff --
done
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