The Oracle ALL_SDO_GEOM_METADATA contains metadata about all
the Geometry columns in all tables, but it doesn't store a specific Geometry type,
so there's no way to tell up-front the type of a given column.
Each column can contain a mix of different Geometries (Points, Polygons, etc.).
The OracleDataStore may try to determine to exact Geometry type by looking
at the Geometry stored in the first record.
This has two drawbacks, the first is about speed, the second is that a table
may be empty.
Or we can add a metadata table of our own to store such an information,
or maybe there're other ways that I don't know of...