Load data into relational db
This task is part of query data feature.
The new feature means people can get part of data object by specifying a sql
query. If the data object is in a relational db, the sql query can be excuted
directly. Unfortunately, data object is not in a relational db in some
systems(e.g. Metacat, kepler local data). So we need load data object into a db.
The first step, we need to write a parser to parse metadata and get DDL for data
object. Then we use the DDL to load the data inot (SAS, DB, R).