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
|
# -*- coding: utf-8 -*-
# mp_safe_db.py
# Copyright (C) 2014 LEAP
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Multiprocessing-safe SQLite database.
"""
from threading import Thread
from Queue import Queue
from pysqlcipher import dbapi2
# Thanks to http://code.activestate.com/recipes/526618/
class MPSafeSQLiteDB(Thread):
"""
A multiprocessing-safe SQLite database accessor.
"""
CLOSE = "--close--"
NO_MORE = "--no more--"
def __init__(self, db_path):
"""
Initialize the process
"""
Thread.__init__(self)
self._db_path = db_path
self._requests = Queue()
self.start()
def run(self):
"""
Run the multiprocessing-safe database accessor.
"""
conn = dbapi2.connect(self._db_path)
while True:
req, arg, res = self._requests.get()
if req == self.CLOSE:
break
with conn:
cursor = conn.cursor()
cursor.execute(req, arg)
if res:
for rec in cursor.fetchall():
res.put(rec)
res.put(self.NO_MORE)
conn.close()
def execute(self, req, arg=None, res=None):
"""
Execute a request on the database.
:param req: The request to be executed.
:type req: str
:param arg: The arguments for the request.
:type arg: tuple
:param res: A queue to write request results.
:type res: multiprocessing.Queue
"""
self._requests.put((req, arg or tuple(), res))
def select(self, req, arg=None):
"""
Run a select query on the database and yield results.
:param req: The request to be executed.
:type req: str
:param arg: The arguments for the request.
:type arg: tuple
"""
res = Queue()
self.execute(req, arg, res)
while True:
rec = res.get()
if rec == self.NO_MORE:
break
yield rec
def close(self):
"""
Close the database connection.
"""
self.execute(self.CLOSE)
self.join()
def cursor(self):
"""
Return a fake cursor object.
Not really a cursor, but allows for calling db.cursor().execute().
:return: Self.
:rtype: MPSafeSQLiteDatabase
"""
return self
|
