Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/16626#discussion_r106472274
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/command/tables.scala ---
@@ -175,6 +178,87 @@ 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)
+
+ try {
+ sparkSession.catalog.uncacheTable(table.unquotedString)
+ } catch {
+ case NonFatal(e) =>
+ log.warn(s"Exception when attempting to uncache table
${table.unquotedString}", 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 newSchemaFields = catalogTable.schema
+ .take(catalogTable.schema.length -
catalogTable.partitionColumnNames.length) ++
+ columns ++ partitionFields
+ checkDuplication(newSchemaFields.map(_.name))
+ catalog.alterTableSchema(table, newSchema =
+ catalogTable.schema.copy(fields = newSchemaFields.toArray))
+
+ Seq.empty[Row]
+ }
+
+ private def checkDuplication(colNames: Seq[String]): Unit = {
+ if (colNames.distinct.length != colNames.length) {
+ val duplicateColumns = colNames.groupBy(identity).collect {
+ case (x, ys) if ys.length > 1 => x
+ }
+ throw new AnalysisException(
+ s"Found duplicate column(s): ${duplicateColumns.mkString(", ")}")
+ }
+ }
+
+ /**
+ * ALTER TABLE ADD COLUMNS command does not support temporary view/table,
+ * view, or datasource table with text, orc formats or external provider.
+ * For datasource table, it currently only supports parquet, json, csv.
+ */
+ private def verifyAlterTableAddColumn(
+ catalog: SessionCatalog,
+ table: TableIdentifier): CatalogTable = {
+ val catalogTable = catalog.getTempViewOrPermanentTableMetadata(table)
+
+ if (catalogTable.tableType == CatalogTableType.VIEW) {
+ throw new AnalysisException(
+ s"${table.toString} is a VIEW, which does not support ALTER ADD
COLUMNS.")
--- End diff --
How about?
> ALTER ADD COLUMNS does not support views. You must drop and re-create the
views for adding the new columns. Views: $table.
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