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
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
|
import sqlalchemy as sa
from sqlalchemy.sql.expression import asc, desc
from .database import has_unique_index
from .orm import get_query_descriptor, get_tables
class QuerySorterException(Exception):
pass
class QuerySorter(object):
def __init__(self, silent=True, separator='-'):
self.separator = separator
self.silent = silent
def assign_order_by(self, entity, attr, func):
expr = get_query_descriptor(self.query, entity, attr)
if expr is not None:
return self.query.order_by(func(expr))
if not self.silent:
raise QuerySorterException(
"Could not sort query with expression '%s'" % attr
)
return self.query
def parse_sort_arg(self, arg):
if arg[0] == self.separator:
func = desc
arg = arg[1:]
else:
func = asc
parts = arg.split(self.separator)
return {
'entity': parts[0] if len(parts) > 1 else None,
'attr': parts[1] if len(parts) > 1 else arg,
'func': func
}
def __call__(self, query, *args):
self.query = query
for sort in args:
if not sort:
continue
self.query = self.assign_order_by(
**self.parse_sort_arg(sort)
)
return self.query
def sort_query(query, *args, **kwargs):
"""
Applies an sql ORDER BY for given query. This function can be easily used
with user-defined sorting.
The examples use the following model definition:
::
import sqlalchemy as sa
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy_utils import sort_query
engine = create_engine(
'sqlite:///'
)
Base = declarative_base()
Session = sessionmaker(bind=engine)
session = Session()
class Category(Base):
__tablename__ = 'category'
id = sa.Column(sa.Integer, primary_key=True)
name = sa.Column(sa.Unicode(255))
class Article(Base):
__tablename__ = 'article'
id = sa.Column(sa.Integer, primary_key=True)
name = sa.Column(sa.Unicode(255))
category_id = sa.Column(sa.Integer, sa.ForeignKey(Category.id))
category = sa.orm.relationship(
Category, primaryjoin=category_id == Category.id
)
1. Applying simple ascending sort
::
query = session.query(Article)
query = sort_query(query, 'name')
2. Appying descending sort
::
query = sort_query(query, '-name')
3. Applying sort to custom calculated label
::
query = session.query(
Category, sa.func.count(Article.id).label('articles')
)
query = sort_query(query, 'articles')
4. Applying sort to joined table column
::
query = session.query(Article).join(Article.category)
query = sort_query(query, 'category-name')
:param query:
query to be modified
:param sort:
string that defines the label or column to sort the query by
:param silent:
Whether or not to raise exceptions if unknown sort column
is passed. By default this is `True` indicating that no errors should
be raised for unknown columns.
"""
return QuerySorter(**kwargs)(query, *args)
def make_order_by_deterministic(query):
"""
Make query order by deterministic (if it isn't already). Order by is
considered deterministic if it contains column that is unique index (
either it is a primary key or has a unique index). Many times it is design
flaw to order by queries in nondeterministic manner.
Consider a User model with three fields: id (primary key), favorite color
and email (unique).::
from sqlalchemy_utils import make_order_by_deterministic
query = session.query(User).order_by(User.favorite_color)
query = make_order_by_deterministic(query)
print query # 'SELECT ... ORDER BY "user".favorite_color, "user".id'
query = session.query(User).order_by(User.email)
query = make_order_by_deterministic(query)
print query # 'SELECT ... ORDER BY "user".email'
query = session.query(User).order_by(User.id)
query = make_order_by_deterministic(query)
print query # 'SELECT ... ORDER BY "user".id'
.. versionadded: 0.27.1
"""
order_by_func = sa.asc
if not query._order_by:
column = None
else:
order_by = query._order_by[0]
if isinstance(order_by, sa.sql.expression.UnaryExpression):
if order_by.modifier == sa.sql.operators.desc_op:
order_by_func = sa.desc
else:
order_by_func = sa.asc
column = order_by.get_children()[0]
else:
column = order_by
# Skip queries that are ordered by an already deterministic column
if isinstance(column, sa.Column):
try:
if has_unique_index(column):
return query
except TypeError:
pass
base_table = get_tables(query._entities[0])[0]
query = query.order_by(
*(order_by_func(c) for c in base_table.c if c.primary_key)
)
return query
|
