Inconsistent metadata handling with ALTER TABLE

Schema changes made with ALTER TABLE are not shown in DESCRIBE TABLE. The table in question was created with HiveContext.read.json().

Steps:

1. alter table dimension_components add columns (z string); succeeds.
2. describe dimension_components; does not show the new column, even after restarting spark-sql.
3. A second alter table dimension_components add columns (z string); fails with RROR exec.DDLTask: org.apache.hadoop.hive.ql.metadata.HiveException: Duplicate column name: z

Full spark-sql output here.