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
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
|
#!/usr/bin/env python
import threading
import unittest
import psycopg2
from psycopg2.extensions import (
ISOLATION_LEVEL_SERIALIZABLE, STATUS_BEGIN, STATUS_READY)
import tests
class TransactionTests(unittest.TestCase):
def setUp(self):
self.conn = psycopg2.connect(tests.dsn)
self.conn.set_isolation_level(ISOLATION_LEVEL_SERIALIZABLE)
curs = self.conn.cursor()
curs.execute('''
CREATE TEMPORARY TABLE table1 (
id int PRIMARY KEY
)''')
# The constraint is set to deferrable for the commit_failed test
curs.execute('''
CREATE TEMPORARY TABLE table2 (
id int PRIMARY KEY,
table1_id int,
CONSTRAINT table2__table1_id__fk
FOREIGN KEY (table1_id) REFERENCES table1(id) DEFERRABLE)''')
curs.execute('INSERT INTO table1 VALUES (1)')
curs.execute('INSERT INTO table2 VALUES (1, 1)')
self.conn.commit()
def tearDown(self):
self.conn.close()
def test_rollback(self):
# Test that rollback undoes changes
curs = self.conn.cursor()
curs.execute('INSERT INTO table2 VALUES (2, 1)')
# Rollback takes us from BEGIN state to READY state
self.assertEqual(self.conn.status, STATUS_BEGIN)
self.conn.rollback()
self.assertEqual(self.conn.status, STATUS_READY)
curs.execute('SELECT id, table1_id FROM table2 WHERE id = 2')
self.assertEqual(curs.fetchall(), [])
def test_commit(self):
# Test that commit stores changes
curs = self.conn.cursor()
curs.execute('INSERT INTO table2 VALUES (2, 1)')
# Rollback takes us from BEGIN state to READY state
self.assertEqual(self.conn.status, STATUS_BEGIN)
self.conn.commit()
self.assertEqual(self.conn.status, STATUS_READY)
# Now rollback and show that the new record is still there:
self.conn.rollback()
curs.execute('SELECT id, table1_id FROM table2 WHERE id = 2')
self.assertEqual(curs.fetchall(), [(2, 1)])
def test_failed_commit(self):
# Test that we can recover from a failed commit.
# We use a deferred constraint to cause a failure on commit.
curs = self.conn.cursor()
curs.execute('SET CONSTRAINTS table2__table1_id__fk DEFERRED')
curs.execute('INSERT INTO table2 VALUES (2, 42)')
# The commit should fail, and move the cursor back to READY state
self.assertEqual(self.conn.status, STATUS_BEGIN)
self.assertRaises(psycopg2.IntegrityError, self.conn.commit)
self.assertEqual(self.conn.status, STATUS_READY)
# The connection should be ready to use for the next transaction:
curs.execute('SELECT 1')
self.assertEqual(curs.fetchone()[0], 1)
class DeadlockSerializationTests(unittest.TestCase):
"""Test deadlock and serialization failure errors."""
def connect(self):
conn = psycopg2.connect(tests.dsn)
conn.set_isolation_level(ISOLATION_LEVEL_SERIALIZABLE)
return conn
def setUp(self):
self.conn = self.connect()
curs = self.conn.cursor()
# Drop table if it already exists
try:
curs.execute("DROP TABLE table1")
self.conn.commit()
except psycopg2.DatabaseError:
self.conn.rollback()
try:
curs.execute("DROP TABLE table2")
self.conn.commit()
except psycopg2.DatabaseError:
self.conn.rollback()
# Create sample data
curs.execute("""
CREATE TABLE table1 (
id int PRIMARY KEY,
name text)
""")
curs.execute("INSERT INTO table1 VALUES (1, 'hello')")
curs.execute("CREATE TABLE table2 (id int PRIMARY KEY)")
self.conn.commit()
def tearDown(self):
curs = self.conn.cursor()
curs.execute("DROP TABLE table1")
curs.execute("DROP TABLE table2")
self.conn.commit()
self.conn.close()
def test_deadlock(self):
self.thread1_error = self.thread2_error = None
step1 = threading.Event()
step2 = threading.Event()
def task1():
try:
conn = self.connect()
curs = conn.cursor()
curs.execute("LOCK table1 IN ACCESS EXCLUSIVE MODE")
step1.set()
step2.wait()
curs.execute("LOCK table2 IN ACCESS EXCLUSIVE MODE")
except psycopg2.DatabaseError, exc:
self.thread1_error = exc
step1.set()
conn.close()
def task2():
try:
conn = self.connect()
curs = conn.cursor()
step1.wait()
curs.execute("LOCK table2 IN ACCESS EXCLUSIVE MODE")
step2.set()
curs.execute("LOCK table1 IN ACCESS EXCLUSIVE MODE")
except psycopg2.DatabaseError, exc:
self.thread2_error = exc
step2.set()
conn.close()
# Run the threads in parallel. The "step1" and "step2" events
# ensure that the two transactions overlap.
thread1 = threading.Thread(target=task1)
thread2 = threading.Thread(target=task2)
thread1.start()
thread2.start()
thread1.join()
thread2.join()
# Exactly one of the threads should have failed with
# TransactionRollbackError:
self.assertFalse(self.thread1_error and self.thread2_error)
error = self.thread1_error or self.thread2_error
self.assertTrue(isinstance(
error, psycopg2.extensions.TransactionRollbackError))
def test_serialisation_failure(self):
self.thread1_error = self.thread2_error = None
step1 = threading.Event()
step2 = threading.Event()
def task1():
try:
conn = self.connect()
curs = conn.cursor()
curs.execute("SELECT name FROM table1 WHERE id = 1")
curs.fetchall()
step1.set()
step2.wait()
curs.execute("UPDATE table1 SET name='task1' WHERE id = 1")
conn.commit()
except psycopg2.DatabaseError, exc:
self.thread1_error = exc
step1.set()
conn.close()
def task2():
try:
conn = self.connect()
curs = conn.cursor()
step1.wait()
curs.execute("UPDATE table1 SET name='task2' WHERE id = 1")
conn.commit()
except psycopg2.DatabaseError, exc:
self.thread2_error = exc
step2.set()
conn.close()
# Run the threads in parallel. The "step1" and "step2" events
# ensure that the two transactions overlap.
thread1 = threading.Thread(target=task1)
thread2 = threading.Thread(target=task2)
thread1.start()
thread2.start()
thread1.join()
thread2.join()
# Exactly one of the threads should have failed with
# TransactionRollbackError:
self.assertFalse(self.thread1_error and self.thread2_error)
error = self.thread1_error or self.thread2_error
self.assertTrue(isinstance(
error, psycopg2.extensions.TransactionRollbackError))
class QueryCancelationTests(unittest.TestCase):
"""Tests for query cancelation."""
def setUp(self):
self.conn = psycopg2.connect(tests.dsn)
self.conn.set_isolation_level(ISOLATION_LEVEL_SERIALIZABLE)
def test_statement_timeout(self):
curs = self.conn.cursor()
# Set a low statement timeout, then sleep for a longer period.
curs.execute('SET statement_timeout TO 10')
self.assertRaises(psycopg2.extensions.QueryCanceledError,
curs.execute, 'SELECT pg_sleep(50)')
def test_suite():
return unittest.TestLoader().loadTestsFromName(__name__)
|