[GNUe-dev] Sort-Order of Null values

[Johannes Vetter]

Hi,

Since most of the database-backends can or do handle sort-order of
null-values differently, we made appserver able to be very flexible. 
There are two new configuration settings for gnue.conf now:

null_first_asc = True/False
null_first_dsc = True/False

Using these settings you can define wether null values are sorted at the
beginning or the end of a resultset. use 'null_first_asc' for ascending
sort order, and 'null_first_dsc' for descending sort order.

Additionally I did some changes to NullObjects in the language
interface. If you access a reference property of a class which is NULL,
you'll get a NullObject instance. If you access a non-reference-property
of a NullObject or another instance None will be returned. 

Example: if a person has no country assigned

address_person.address_country  --> NullObject
address_perons.address_country.address_name  --> None
x = address_person.address_country
y = x.address_name
x --> NullObject
y --> None

This means to you: you will always get None if you access a
non-reference property. you will always get a NullObject if you access a
reference property which is Null. following access to this NullObject is
possible and handled according to the classrepository.

Comparing:

x = NullObject
y = None
z = 'foo'

x == y  True
x !=    False
x < z   True

cmp (x, y)      0
cmp (x, z)      -1
cmp (x, y)      0


Thanks,
Johannes
 

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