compute_prefix
Description:
Computes the common prefix that is shared by all rows in this that start with key.
If no row matches key, null will be returned. Note that a text column must have been set for
this function to work, see set_text_column for details.
Parameters:
| this |
the entry completion |
| key |
The text to complete for |
Returns:
|
The common prefix all rows starting with |