/bangkokhotel/lib/python2.5/site-packages/django/db/models/sql/expressions.py

 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