/bangkokhotel/lib/python2.5/site-packages/django/db/models/sql/expressions.py
Python | 97 lines | 72 code | 19 blank | 6 comment | 23 complexity | 8d1a6d3bdc8f809409646947962d7e40 MD5 | raw file
1from django.core.exceptions import FieldError
2from django.db.models.fields import FieldDoesNotExist
3from django.db.models.sql.constants import LOOKUP_SEP
4
5class SQLEvaluator(object):
6 def __init__(self, expression, query, allow_joins=True):
7 self.expression = expression
8 self.opts = query.get_meta()
9 self.cols = {}
10
11 self.contains_aggregate = False
12 self.expression.prepare(self, query, allow_joins)
13
14 def prepare(self):
15 return self
16
17 def as_sql(self, qn, connection):
18 return self.expression.evaluate(self, qn, connection)
19
20 def relabel_aliases(self, change_map):
21 for node, col in self.cols.items():
22 if hasattr(col, "relabel_aliases"):
23 col.relabel_aliases(change_map)
24 else:
25 self.cols[node] = (change_map.get(col[0], col[0]), col[1])
26
27 #####################################################
28 # Vistor methods for initial expression preparation #
29 #####################################################
30
31 def prepare_node(self, node, query, allow_joins):
32 for child in node.children:
33 if hasattr(child, 'prepare'):
34 child.prepare(self, query, allow_joins)
35
36 def prepare_leaf(self, node, query, allow_joins):
37 if not allow_joins and LOOKUP_SEP in node.name:
38 raise FieldError("Joined field references are not permitted in this query")
39
40 field_list = node.name.split(LOOKUP_SEP)
41 if (len(field_list) == 1 and
42 node.name in query.aggregate_select.keys()):
43 self.contains_aggregate = True
44 self.cols[node] = query.aggregate_select[node.name]
45 else:
46 try:
47 field, source, opts, join_list, last, _ = query.setup_joins(
48 field_list, query.get_meta(),
49 query.get_initial_alias(), False)
50 col, _, join_list = query.trim_joins(source, join_list, last, False)
51
52 self.cols[node] = (join_list[-1], col)
53 except FieldDoesNotExist:
54 raise FieldError("Cannot resolve keyword %r into field. "
55 "Choices are: %s" % (self.name,
56 [f.name for f in self.opts.fields]))
57
58 ##################################################
59 # Vistor methods for final expression evaluation #
60 ##################################################
61
62 def evaluate_node(self, node, qn, connection):
63 expressions = []
64 expression_params = []
65 for child in node.children:
66 if hasattr(child, 'evaluate'):
67 sql, params = child.evaluate(self, qn, connection)
68 else:
69 sql, params = '%s', (child,)
70
71 if len(getattr(child, 'children', [])) > 1:
72 format = '(%s)'
73 else:
74 format = '%s'
75
76 if sql:
77 expressions.append(format % sql)
78 expression_params.extend(params)
79
80 return connection.ops.combine_expression(node.connector, expressions), expression_params
81
82 def evaluate_leaf(self, node, qn, connection):
83 col = self.cols[node]
84 if hasattr(col, 'as_sql'):
85 return col.as_sql(qn, connection), ()
86 else:
87 return '%s.%s' % (qn(col[0]), qn(col[1])), ()
88
89 def evaluate_date_modifier_node(self, node, qn, connection):
90 timedelta = node.children.pop()
91 sql, params = self.evaluate_node(node, qn, connection)
92
93 if timedelta.days == 0 and timedelta.seconds == 0 and \
94 timedelta.microseconds == 0:
95 return sql, params
96
97 return connection.ops.date_interval_sql(sql, node.connector, timedelta), params