It looks like we can add columns to existing tables via: ALTER TABLE table_name ADD|REPLACE COLUMNS (col_name data_type [COMMENT col_comment], ...)
However, I see the following comment in the Hive docs: "NOTE: These commands will only modify Hive's metadata, and will NOT reorganize or reformat existing data. Users should make sure the actual data layout conforms with the metadata definition." Question: If we already have a table that has lots of data in it, and I execute the above statement to add a column, will I still be able to query existing data? Or do I need to re-import somehow all of the data and fill in a value for the new column? The idea is to be able to add a new column, and make sure that the column value exists for all NEW partitions in the same table. I would hate to have to reload all of the old data just to specify a NULL value for the new column. Will this work as expected or a data re-load is necessary every time we add a new column to be able to still query older data? Thanks! Ryan
