------------------------
- The ``HAVING`` clause for aggregate queries is now supported.
- The ``empty()`` BQL function to determine whether an Inventory
object as returned by the ``sum()`` aggregate function is empty has
been added.
- Added the ``round()`` BQL function.
- ``NULL`` values in ``SORT BY`` clause are now always considered to
be smaller than any other values. This may results in rows to be
returned in a slightly different order.
- It is now possible to specify the direction of the ordering for each
column in the ``SORT BY`` clause. This brings BQL closer to SQL
specification but queries written with the old behaviour in mind
will return rows in a different order. The query::
SELECT date, narration ORDER BY date, narration DESC
used to return rows in descending order by both ``date`` and
``narration`` while now it would order the rows ascending by
``date`` and descending by ``narration``. To recover the old
behavior, the query should be written::
SELECT date, narration ORDER BY date DESC, narration DESC
- Type casting functions ``int()``, ``decimal()``, ``str()``,
``date()`` have been added. These are mostly useful to convert the
generic ``object`` type returned by the metadata retrieval functions
but can also be used to convert between types. If the conversion
fails, ``NULL`` is returned.
- The ``str()`` BQL function used to return a string representation of
its argument using the Python :py:func:`repr()` function. This
clashes with the use of ``str()`` as a type casting function. The
function is renamed ``repr()``.
- The ``date()`` BQL function used to extract a date from string
arguments with a very relaxed parser. This clashes with the use of
``date()`` as a type casting function. The function is renamed
``parse_date()``. Another form of ``parse_date()`` that accepts the
date format as second argument has been added.
- The ``getitem()`` BQL function return type has been changed from a
string to a generic ``object`` to match the return type of function
retrieving entries from metadata dictionaries. The old behavior can
be obtained with ``str(getitem(x, key))``.