Cannot apped to dataframe with 0 rows

[vasil-pashov]

trafficstars

In case there are no rows in the initial dataframe the index is set to be datetime index. There is no particular reasoning behind this choice. This makes it impossible to append row-range indexed dataframe to the empty one.

• (Static schema) We must be able to append anything to a 0-rowed dataframe regardless of the type of the index and types of the other columns as long as non-index columns match in name and order. The first non-empty dataframe used for either append or update will determine the types of all columns.
• (Dynamic schema) We must be able to append anything to a 0-rowed dataframe regardless of column types. Initially the columns are of empty type (and the index is of empty index type). The first non-empty append/update will determine the type of the columns.