Github user yhuai commented on a diff in the pull request:
https://github.com/apache/spark/pull/12121#discussion_r58297825
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/command/ddl.scala ---
@@ -312,11 +378,38 @@ case class AlterTableSetFileFormat(
genericFormat: Option[String])(sql: String)
extends NativeDDLCommand(sql) with Logging
+/**
+ * A command that sets the location of a table or a partition.
+ *
+ * The syntax of this command is:
+ * {{{
+ * ALTER TABLE table_name [PARTITION partition_spec] SET LOCATION "loc";
+ * }}}
+ */
case class AlterTableSetLocation(
tableName: TableIdentifier,
partitionSpec: Option[TablePartitionSpec],
- location: String)(sql: String)
- extends NativeDDLCommand(sql) with Logging
+ location: String)
+ extends RunnableCommand {
+
+ override def run(sqlContext: SQLContext): Seq[Row] = {
+ val catalog = sqlContext.sessionState.catalog
+ if (partitionSpec.isEmpty) {
+ // No partition spec is specified, so we set the location for the
table itself
+ val table = catalog.getTable(tableName)
+ val newTable = table.withNewStorage(locationUri = Some(location))
+ catalog.alterTable(newTable)
+ } else {
+ // Partition spec is specified, so we set the location only for this
partition
+ val spec = partitionSpec.get
+ val part = catalog.getPartition(tableName, spec)
+ val newPart = part.copy(storage = part.storage.copy(locationUri =
Some(location)))
+ catalog.alterPartitions(tableName, Seq(newPart))
+ }
+ Seq.empty[Row]
+ }
+
+}
--- End diff --
I think for data source tables, we cannot do `ALTER TABLE table_name
PARTITION partition_spec SET LOCATION` because we rely on our partitioning
discovery mechanism. Also, for data source tables, the real path is stored in
table properties (there is a path field). We need to change that as well as the
locationUri.
Also, I think it's good to document clearly on the semantic of this
command. For a user, he/she needs to know if this command will move the data to
the new location. For Hive, it does not move data. For now, I think it is fine
to match that behavior, but we need to document it.
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