diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala index 17f7f9fe51376a79141cd5e789af7cb498539c45..3dd7d38847b44c20ae1f3bf6f24bf805db548eac 100644 --- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala +++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala @@ -95,9 +95,12 @@ abstract class Attribute extends NamedExpression { * @param name the name to be associated with the result of computing [[child]]. * @param exprId A globally unique id used to check if an [[AttributeReference]] refers to this * alias. Auto-assigned if left blank. + * @param explicitMetadata Explicit metadata associated with this alias that overwrites child's. */ -case class Alias(child: Expression, name: String) - (val exprId: ExprId = NamedExpression.newExprId, val qualifiers: Seq[String] = Nil) +case class Alias(child: Expression, name: String)( + val exprId: ExprId = NamedExpression.newExprId, + val qualifiers: Seq[String] = Nil, + val explicitMetadata: Option[Metadata] = None) extends NamedExpression with trees.UnaryNode[Expression] { override type EvaluatedType = Any @@ -107,9 +110,11 @@ case class Alias(child: Expression, name: String) override def dataType = child.dataType override def nullable = child.nullable override def metadata: Metadata = { - child match { - case named: NamedExpression => named.metadata - case _ => Metadata.empty + explicitMetadata.getOrElse { + child match { + case named: NamedExpression => named.metadata + case _ => Metadata.empty + } } } @@ -123,11 +128,12 @@ case class Alias(child: Expression, name: String) override def toString: String = s"$child AS $name#${exprId.id}$typeSuffix" - override protected final def otherCopyArgs = exprId :: qualifiers :: Nil + override protected final def otherCopyArgs = exprId :: qualifiers :: explicitMetadata :: Nil override def equals(other: Any): Boolean = other match { case a: Alias => - name == a.name && exprId == a.exprId && child == a.child && qualifiers == a.qualifiers + name == a.name && exprId == a.exprId && child == a.child && qualifiers == a.qualifiers && + explicitMetadata == a.explicitMetadata case _ => false } } diff --git a/sql/core/src/main/scala/org/apache/spark/sql/Column.scala b/sql/core/src/main/scala/org/apache/spark/sql/Column.scala index ec7d15f5bc4e76a5db8c78d554694cd9869684d5..2ae47e07d45ec83c0cfd4bf17aa8c43f4ca0f3fe 100644 --- a/sql/core/src/main/scala/org/apache/spark/sql/Column.scala +++ b/sql/core/src/main/scala/org/apache/spark/sql/Column.scala @@ -594,6 +594,19 @@ class Column(protected[sql] val expr: Expression) { */ def as(alias: Symbol): Column = Alias(expr, alias.name)() + /** + * Gives the column an alias with metadata. + * {{{ + * val metadata: Metadata = ... + * df.select($"colA".as("colB", metadata)) + * }}} + * + * @group expr_ops + */ + def as(alias: String, metadata: Metadata): Column = { + Alias(expr, alias)(explicitMetadata = Some(metadata)) + } + /** * Casts the column to a different data type. * {{{ diff --git a/sql/core/src/test/scala/org/apache/spark/sql/ColumnExpressionSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/ColumnExpressionSuite.scala index a53ae97d6243ac6a7508c28d47a787ac1a790092..bc8fae100db6a1be5f3d08cdec974b1b4f63a568 100644 --- a/sql/core/src/test/scala/org/apache/spark/sql/ColumnExpressionSuite.scala +++ b/sql/core/src/test/scala/org/apache/spark/sql/ColumnExpressionSuite.scala @@ -17,12 +17,10 @@ package org.apache.spark.sql -import org.apache.spark.sql.catalyst.expressions.NamedExpression -import org.apache.spark.sql.catalyst.plans.logical.{Project, NoRelation} import org.apache.spark.sql.functions._ import org.apache.spark.sql.test.TestSQLContext import org.apache.spark.sql.test.TestSQLContext.implicits._ -import org.apache.spark.sql.types.{BooleanType, IntegerType, StructField, StructType} +import org.apache.spark.sql.types._ class ColumnExpressionSuite extends QueryTest { @@ -322,4 +320,15 @@ class ColumnExpressionSuite extends QueryTest { assert('key.desc == 'key.desc) assert('key.desc != 'key.asc) } + + test("alias with metadata") { + val metadata = new MetadataBuilder() + .putString("originName", "value") + .build() + val schema = testData + .select($"*", col("value").as("abc", metadata)) + .schema + assert(schema("value").metadata === Metadata.empty) + assert(schema("abc").metadata === metadata) + } }