When select a column family, the only way to figure out all columns inside the column family is to do a scan. Since HBase does not have an API to get column names only, we have to provide a temporary workaround. We can add an option to do full table scan, and we scan small amount of data to figure out the column patterns by default. This short cut make assumption that data are in repeated pattern, scanning one row should be sufficient to find all the columns. The same principle applies in scanning for unique row names.