Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/16626#discussion_r106097589
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/command/tables.scala ---
@@ -175,6 +178,80 @@ case class AlterTableRenameCommand(
}
/**
+ * A command that add columns to a table
+ * The syntax of using this command in SQL is:
+ * {{{
+ * ALTER TABLE table_identifier
+ * ADD COLUMNS (col_name data_type [COMMENT col_comment], ...);
+ * }}}
+*/
+case class AlterTableAddColumnsCommand(
+ table: TableIdentifier,
+ columns: Seq[StructField]) extends RunnableCommand {
+ override def run(sparkSession: SparkSession): Seq[Row] = {
+ val catalog = sparkSession.sessionState.catalog
+ val catalogTable = verifyAlterTableAddColumn(catalog, table)
+
+ // If an exception is thrown here we can just assume the table is
uncached;
+ // this can happen with Hive tables when the underlying catalog is
in-memory.
+ val wasCached =
Try(sparkSession.catalog.isCached(table.unquotedString)).getOrElse(false)
+ if (wasCached) {
+ try {
+ sparkSession.catalog.uncacheTable(table.unquotedString)
+ } catch {
+ case NonFatal(e) => log.warn(e.toString, e)
+ }
+ }
+ // Invalidate the table last, otherwise uncaching the table would load
the logical plan
+ // back into the hive metastore cache
+ catalog.refreshTable(table)
+ val partitionFields =
catalogTable.schema.takeRight(catalogTable.partitionColumnNames.length)
+ val dataSchema = catalogTable.schema
+ .take(catalogTable.schema.length -
catalogTable.partitionColumnNames.length)
+ catalog.alterTableSchema(table, newSchema =
+ catalogTable.schema.copy(fields = (dataSchema ++ columns ++
partitionFields).toArray))
+
+ Seq.empty[Row]
+ }
+
+ /**
+ * ALTER TABLE ADD COLUMNS command does not support temporary view/table,
+ * view, or datasource table with text, orc formats or external provider.
+ * For datasource table, it currently only supports parquet, json, csv.
+ */
+ private def verifyAlterTableAddColumn(
+ catalog: SessionCatalog,
+ table: TableIdentifier): CatalogTable = {
+ val catalogTable = catalog.getTempViewOrPermanentTableMetadata(table)
+
+ if (catalogTable.tableType == CatalogTableType.VIEW) {
+ throw new AnalysisException(
+ s"${table.toString} is a VIEW, which does not support ALTER ADD
COLUMNS.")
+ }
+
+ if (DDLUtils.isDatasourceTable(catalogTable)) {
+ DataSource.lookupDataSource(catalogTable.provider.get).newInstance()
match {
+ // For datasource table, this command can only support the
following File format.
+ // TextFileFormat only default to one column "value"
+ // OrcFileFormat can not handle difference between user-specified
schema and
+ // inferred schema yet. TODO, once this issue is resolved , we can
add Orc back.
+ // Hive type is already considered as hive serde table, so the
logic will not
+ // come in here.
+ case _: JsonFileFormat | _: CSVFileFormat | _: ParquetFileFormat =>
+ case s =>
+ throw new AnalysisException(
+ s"""${table} is a datasource table with type $s,
+ |which does not support ALTER ADD COLUMNS.
+ """.stripMargin)
--- End diff --
Nit:
```Scala
throw new AnalysisException(
s"$table is a datasource table with type $s, which does not
support ALTER ADD COLUMNS.")
```
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