Question

I have a table which looks like this.

+----+--------+---------+-----------+------------------------+
| id | parent | type    | libTypeId | name                   |
+----+--------+---------+-----------+------------------------+
|  2 |      1 | project |         2 | 1p6m4x0y1z_1.2-1.8_hvt |
|  5 |      1 | project |         6 | 1p6m4x0y1z_1.2-1.8_hvt |
|  8 |      1 | project |        16 | 1p6m4x0y1z_1.2-1.8_hvt |
| 11 |      1 | project |        21 | 1p6m4x0y1z_1.2-1.8_hvt |
|  3 |      1 | project |         2 | 1p6m4x0y1z_1.2-1.8_lvt |
|  6 |      1 | project |         6 | 1p6m4x0y1z_1.2-1.8_lvt |
|  9 |      1 | project |        16 | 1p6m4x0y1z_1.2-1.8_lvt |
| 12 |      1 | project |        21 | 1p6m4x0y1z_1.2-1.8_lvt |
|  1 |      1 | project |         2 | 1p6m4x0y1z_1.2-1.8_svt |
|  4 |      1 | project |         6 | 1p6m4x0y1z_1.2-1.8_svt |
|  7 |      1 | project |        16 | 1p6m4x0y1z_1.2-1.8_svt |
| 10 |      1 | project |        21 | 1p6m4x0y1z_1.2-1.8_svt |
| 13 |      2 | project |         2 | 065nm_GPIO             |
| 17 |      2 | project |         4 | 065nm_GPIO             |
| 14 |      2 | project |         6 | 065nm_GPIO             |
| 18 |      2 | project |        12 | 065nm_GPIO             |
| 15 |      2 | project |        16 | 065nm_GPIO             |
| 16 |      2 | project |        21 | 065nm_GPIO             |
| 19 |      2 | project |         2 | 065nm_Specialized      |
+----+--------+---------+-----------+------------------------+

What I am looking for is a query which results in a list where we get all projects with id = 1 which is sorted by name, libtypeid and the FIRST libtypeid only.

In otherwords I should end up with this:

+----+--------+---------+-----------+------------------------+
| id | parent | type    | libTypeId | name                   |
+----+--------+---------+-----------+------------------------+
|  2 |      1 | project |         2 | 1p6m4x0y1z_1.2-1.8_hvt |
|  3 |      1 | project |         2 | 1p6m4x0y1z_1.2-1.8_lvt |
|  1 |      1 | project |         2 | 1p6m4x0y1z_1.2-1.8_svt |
+----+--------+---------+-----------+------------------------+

Now I can get this far but how do I get only the first one??

Variant.objects.filter(parent=self.id).order_by('name', 'libtype_id')

I then further do this..

full = Variant.objects.filter(parent=self.id).order_by('name', 'libtype_id')
names, out = [], []
for v in full:
    if v.name not in names:
       out.append(v)
       names.append(v.name)
return out

Much appreciate if someone can clean this up a bit..

Answer 1

Here is the answer I was looking for..

class VariantQuerySet(QuerySet):
    def as_single_library_type(self):
        query = self.filter().query
        query.group_by = ['name']
        return QuerySet(self.model, using=self._db, query=query)

class VariantManager(models.Manager):

    def get_query_set(self):
        return VariantQuerySet(self.model, using=self._db)

This basically does a default GROUP BY which reduces everything to what I need. Thanks to all who attempted answered!