为什么psycopg2不会为查询引用这些字符串?

使用psycopg2引擎,使用django编写应用程序。它似乎并不总是想引用我的字符串。下面是一个测试用例:

>>> from pypvs.search.models import Addr2zip
>>> kwargs = {
...     'street_name__iexact': 'Common Ground',
...     'state_id__iexact': 'MT',
... }
>>> addrMatch = Addr2zip.objects.extra(
...     where = ['ctystate.zip5 = addr2zip.zip5 AND ctystate.city_name = \'%s\'' % 'Philipsburg'],
...     tables = ['ctystate', 'addr2zip']
... ).filter(**kwargs).order_by('zip5', 'street_name', 'primary_address_low', 'secondary_address_low')
>>> print addrMatch.query
SELECT "addr2zip"."addr2zip_id", "addr2zip"."zip5", "addr2zip"."zip4_low", "addr2zip"."zip4_high", "addr2zip"."street_direction", "addr2zip"."street_name", "addr2zip"."street_suffix", "addr2zip"."street_post_direction", "addr2zip"."primary_address_low", "addr2zip"."primary_address_high", "addr2zip"."primary_address_parity", "addr2zip"."secondary_address", "addr2zip"."secondary_address_low", "addr2zip"."secondary_address_high", "addr2zip"."secondary_address_parity", "addr2zip"."state_id", "addr2zip"."county_code", "addr2zip"."municipality_key", "addr2zip"."urbanization_key", "addr2zip"."record_type" FROM "addr2zip" , "ctystate" WHERE (ctystate.zip5 = addr2zip.zip5 AND ctystate.city_name = Philipsburg AND UPPER("addr2zip"."state_id"::text) = UPPER(MT)  AND UPPER("addr2zip"."street_name"::text) = UPPER(Common Ground) ) ORDER BY "addr2zip"."zip5" ASC, "addr2zip"."street_name" ASC, "addr2zip"."primary_address_low" ASC, "addr2zip"."secondary_address_low" ASC

这些字符串没有被引用的原因是什么?例如,“共同点”:

AND UPPER("addr2zip"."street_name"::text) = UPPER(Common Ground)

不确定问题是否在我的实现、psycopg2或django orm中。我很感激你的任何想法。