Internal refactoring; moving LOOKUP_SEP up one level.

In an ideal world, nothing except django.db.models.query should have to
import stuff from django.models.sql.*. A few things were needing to get
hold of sql.constants.LOOKUP_SEP, so this commit moves it up to
django.db.models.constants.LOOKUP_SEP.

There are still a couple of places (admin) poking into sql.* to get
QUERY_TERMS, which is unfortunate, but a slightly different issue and
harder to adjust.

django/contrib/admin/options.py

@@ -14,9 +14,10 @@ from django.core.exceptions import PermissionDenied, ValidationError
 from django.core.paginator import Paginator
 from django.core.urlresolvers import reverse
 from django.db import models, transaction, router
+from django.db.models.constants import LOOKUP_SEP
 from django.db.models.related import RelatedObject
 from django.db.models.fields import BLANK_CHOICE_DASH, FieldDoesNotExist
-from django.db.models.sql.constants import LOOKUP_SEP, QUERY_TERMS
+from django.db.models.sql.constants import QUERY_TERMS
 from django.http import Http404, HttpResponse, HttpResponseRedirect
 from django.shortcuts import get_object_or_404
 from django.template.response import SimpleTemplateResponse, TemplateResponse

django/contrib/admin/util.py

@@ -4,7 +4,7 @@ import datetime
 import decimal
 
 from django.db import models
-from django.db.models.sql.constants import LOOKUP_SEP
+from django.db.models.constants import LOOKUP_SEP
 from django.db.models.deletion import Collector
 from django.db.models.related import RelatedObject
 from django.forms.forms import pretty_name

django/contrib/gis/db/models/sql/where.py

@@ -1,5 +1,5 @@
+from django.db.models.constants import LOOKUP_SEP
 from django.db.models.fields import FieldDoesNotExist
-from django.db.models.sql.constants import LOOKUP_SEP
 from django.db.models.sql.expressions import SQLEvaluator
 from django.db.models.sql.where import Constraint, WhereNode
 from django.contrib.gis.db.models.fields import GeometryField

django/db/models/constants.py

@@ -0,0 +1,7 @@
+"""
+Constants used across the ORM in general.
+"""
+
+# Separator used to split filter strings apart.
+LOOKUP_SEP = '__'
+

django/db/models/query.py

@@ -8,6 +8,7 @@ import sys
 
 from django.core import exceptions
 from django.db import connections, router, transaction, IntegrityError
+from django.db.models.constants import LOOKUP_SEP
 from django.db.models.fields import AutoField
 from django.db.models.query_utils import (Q, select_related_descend,
     deferred_class_factory, InvalidQuery)
@@ -1613,8 +1614,6 @@ def prefetch_related_objects(result_cache, related_lookups):
     Populates prefetched objects caches for a list of results
     from a QuerySet
     """
-    from django.db.models.sql.constants import LOOKUP_SEP
-
     if len(result_cache) == 0:
         return # nothing to do
 

django/db/models/sql/compiler.py

@@ -3,9 +3,10 @@ from django.utils.six.moves import zip
 from django.core.exceptions import FieldError
 from django.db import transaction
 from django.db.backends.util import truncate_name
+from django.db.models.constants import LOOKUP_SEP
 from django.db.models.query_utils import select_related_descend
 from django.db.models.sql.constants import (SINGLE, MULTI, ORDER_DIR,
-    LOOKUP_SEP, GET_ITERATOR_CHUNK_SIZE)
+        GET_ITERATOR_CHUNK_SIZE)
 from django.db.models.sql.datastructures import EmptyResultSet
 from django.db.models.sql.expressions import SQLEvaluator
 from django.db.models.sql.query import get_order_dir, Query

django/db/models/sql/constants.py

@@ -1,7 +1,13 @@
+"""
+Constants specific to the SQL storage portion of the ORM.
+"""
+
 from collections import namedtuple
 import re
 
-# Valid query types (a set is used for speedy lookups).
+# Valid query types (a set is used for speedy lookups). These are (currently)
+# considered SQL-specific; other storage systems may choose to use different
+# lookup types.
 QUERY_TERMS = set([
     'exact', 'iexact', 'contains', 'icontains', 'gt', 'gte', 'lt', 'lte', 'in',
     'startswith', 'istartswith', 'endswith', 'iendswith', 'range', 'year',
@@ -12,9 +18,6 @@ QUERY_TERMS = set([
 # Larger values are slightly faster at the expense of more storage space.
 GET_ITERATOR_CHUNK_SIZE = 100
 
-# Separator used to split filter strings apart.
-LOOKUP_SEP = '__'
-
 # Constants to make looking up tuple values clearer.
 # Join lists (indexes into the tuples that are values in the alias_map
 # dictionary in the Query class).

django/db/models/sql/expressions.py

@@ -1,6 +1,6 @@
 from django.core.exceptions import FieldError
+from django.db.models.constants import LOOKUP_SEP
 from django.db.models.fields import FieldDoesNotExist
-from django.db.models.sql.constants import LOOKUP_SEP
 
 class SQLEvaluator(object):
     def __init__(self, expression, query, allow_joins=True):

django/db/models/sql/query.py

@@ -15,11 +15,12 @@ from django.utils.tree import Node
 from django.utils import six
 from django.db import connections, DEFAULT_DB_ALIAS
 from django.db.models import signals
+from django.db.models.constants import LOOKUP_SEP
 from django.db.models.expressions import ExpressionNode
 from django.db.models.fields import FieldDoesNotExist
 from django.db.models.sql import aggregates as base_aggregates_module
-from django.db.models.sql.constants import (QUERY_TERMS, LOOKUP_SEP, ORDER_DIR,
-    SINGLE, ORDER_PATTERN, JoinInfo)
+from django.db.models.sql.constants import (QUERY_TERMS, ORDER_DIR, SINGLE,
+        ORDER_PATTERN, JoinInfo)
 from django.db.models.sql.datastructures import EmptyResultSet, Empty, MultiJoin
 from django.db.models.sql.expressions import SQLEvaluator
 from django.db.models.sql.where import (WhereNode, Constraint, EverythingNode,

django/db/models/sql/subqueries.py

@@ -3,6 +3,7 @@ Query subclasses which provide extra functionality beyond simple data retrieval.
 """
 
 from django.core.exceptions import FieldError
+from django.db.models.constants import LOOKUP_SEP
 from django.db.models.fields import DateField, FieldDoesNotExist
 from django.db.models.sql.constants import *
 from django.db.models.sql.datastructures import Date