1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
|
"""
Classes to represent the definitions of aggregate functions.
"""
from django.core.exceptions import FieldError
from django.db.models.expressions import Func, Star
from django.db.models.fields import FloatField, IntegerField
__all__ = [
'Aggregate', 'Avg', 'Count', 'Max', 'Min', 'StdDev', 'Sum', 'Variance',
]
class Aggregate(Func):
contains_aggregate = True
name = None
def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False):
# Aggregates are not allowed in UPDATE queries, so ignore for_save
c = super(Aggregate, self).resolve_expression(query, allow_joins, reuse, summarize)
if not summarize:
expressions = c.get_source_expressions()
for index, expr in enumerate(expressions):
if expr.contains_aggregate:
before_resolved = self.get_source_expressions()[index]
name = before_resolved.name if hasattr(before_resolved, 'name') else repr(before_resolved)
raise FieldError("Cannot compute %s('%s'): '%s' is an aggregate" % (c.name, name, name))
c._patch_aggregate(query) # backward-compatibility support
return c
@property
def default_alias(self):
expressions = self.get_source_expressions()
if len(expressions) == 1 and hasattr(expressions[0], 'name'):
return '%s__%s' % (expressions[0].name, self.name.lower())
raise TypeError("Complex expressions require an alias")
def get_group_by_cols(self):
return []
def _patch_aggregate(self, query):
"""
Helper method for patching 3rd party aggregates that do not yet support
the new way of subclassing. This method will be removed in Django 1.10.
add_to_query(query, alias, col, source, is_summary) will be defined on
legacy aggregates which, in turn, instantiates the SQL implementation of
the aggregate. In all the cases found, the general implementation of
add_to_query looks like:
def add_to_query(self, query, alias, col, source, is_summary):
klass = SQLImplementationAggregate
aggregate = klass(col, source=source, is_summary=is_summary, **self.extra)
query.aggregates[alias] = aggregate
By supplying a known alias, we can get the SQLAggregate out of the
aggregates dict, and use the sql_function and sql_template attributes
to patch *this* aggregate.
"""
if not hasattr(self, 'add_to_query') or self.function is not None:
return
placeholder_alias = "_XXXXXXXX_"
self.add_to_query(query, placeholder_alias, None, None, None)
sql_aggregate = query.aggregates.pop(placeholder_alias)
if 'sql_function' not in self.extra and hasattr(sql_aggregate, 'sql_function'):
self.extra['function'] = sql_aggregate.sql_function
if hasattr(sql_aggregate, 'sql_template'):
self.extra['template'] = sql_aggregate.sql_template
class Avg(Aggregate):
function = 'AVG'
name = 'Avg'
def __init__(self, expression, **extra):
output_field = extra.pop('output_field', FloatField())
super(Avg, self).__init__(expression, output_field=output_field, **extra)
def as_oracle(self, compiler, connection):
if self.output_field.get_internal_type() == 'DurationField':
expression = self.get_source_expressions()[0]
from django.db.backends.oracle.functions import IntervalToSeconds, SecondsToInterval
return compiler.compile(
SecondsToInterval(Avg(IntervalToSeconds(expression)))
)
return super(Avg, self).as_sql(compiler, connection)
class Count(Aggregate):
function = 'COUNT'
name = 'Count'
template = '%(function)s(%(distinct)s%(expressions)s)'
def __init__(self, expression, distinct=False, **extra):
if expression == '*':
expression = Star()
super(Count, self).__init__(
expression, distinct='DISTINCT ' if distinct else '', output_field=IntegerField(), **extra)
def __repr__(self):
return "{}({}, distinct={})".format(
self.__class__.__name__,
self.arg_joiner.join(str(arg) for arg in self.source_expressions),
'False' if self.extra['distinct'] == '' else 'True',
)
def convert_value(self, value, expression, connection, context):
if value is None:
return 0
return int(value)
class Max(Aggregate):
function = 'MAX'
name = 'Max'
class Min(Aggregate):
function = 'MIN'
name = 'Min'
class StdDev(Aggregate):
name = 'StdDev'
def __init__(self, expression, sample=False, **extra):
self.function = 'STDDEV_SAMP' if sample else 'STDDEV_POP'
super(StdDev, self).__init__(expression, output_field=FloatField(), **extra)
def __repr__(self):
return "{}({}, sample={})".format(
self.__class__.__name__,
self.arg_joiner.join(str(arg) for arg in self.source_expressions),
'False' if self.function == 'STDDEV_POP' else 'True',
)
def convert_value(self, value, expression, connection, context):
if value is None:
return value
return float(value)
class Sum(Aggregate):
function = 'SUM'
name = 'Sum'
def as_oracle(self, compiler, connection):
if self.output_field.get_internal_type() == 'DurationField':
expression = self.get_source_expressions()[0]
from django.db.backends.oracle.functions import IntervalToSeconds, SecondsToInterval
return compiler.compile(
SecondsToInterval(Sum(IntervalToSeconds(expression)))
)
return super(Sum, self).as_sql(compiler, connection)
class Variance(Aggregate):
name = 'Variance'
def __init__(self, expression, sample=False, **extra):
self.function = 'VAR_SAMP' if sample else 'VAR_POP'
super(Variance, self).__init__(expression, output_field=FloatField(), **extra)
def __repr__(self):
return "{}({}, sample={})".format(
self.__class__.__name__,
self.arg_joiner.join(str(arg) for arg in self.source_expressions),
'False' if self.function == 'VAR_POP' else 'True',
)
def convert_value(self, value, expression, connection, context):
if value is None:
return value
return float(value)
|
