return null;
}
D datastore = getPreviewDatastore(filename);
DataContextProvider dcp = datastore.getDataContextProvider();
DataContext dc = dcp.getDataContext();
Table table = getPreviewTable(dc);
Column[] columns = table.getColumns();
if (columns.length > getPreviewColumns()) {
// include max 10 columns
columns = Arrays.copyOf(columns, getPreviewColumns());
}
Query q = dc.query().from(table).select(columns).toQuery();