我想在 python 中创建一个 :memory: 数据库并从不同的线程访问它。 本质上是这样的:

class T(threading.Thread):
    def run(self):
        self.conn = sqlite3.connect(':memory:')
        # do stuff with the database

for i in xrange(N):
    T().start()

并且所有连接都指向同一个数据库。

我知道将 check_same_thread=True 传递给连接函数并共享 线程之间的连接，但希望尽可能避免这样做。感谢您的帮助。

编辑:更正了一个拼写错误。我最初说“让所有连接都引用同一个线程”用线程代替数据库。

最佳答案

SQLite 在过去 4 年中得到了改进，因此现在共享内存数据库成为可能。检查以下代码:

import sqlite3

foobar_uri = 'file:foobar_database?mode=memory&cache=shared'
not_really_foobar_uri = 'file:not_really_foobar?mode=memory&cache=shared'

# connect to databases in no particular order
db2 = sqlite3.connect(foobar_uri, uri=True)
db_lol = sqlite3.connect(not_really_foobar_uri, uri=True)
db1 = sqlite3.connect(foobar_uri, uri=True)

# create cursor as db2
cur2 = db2.cursor()

# create table as db2
db2.execute('CREATE TABLE foo (NUMBER bar)')

# insert values as db1
db1.execute('INSERT INTO foo VALUES (42)')
db1.commit()

# and fetch them from db2 through cur2
cur2.execute('SELECT * FROM foo')
print(cur2.fetchone()[0])  # 42

# test that db_lol is not shared with db1 and db2
try:
    db_lol.cursor().execute('SELECT * FROM foo')
except sqlite3.OperationalError as exc:
    print(exc)  # just as expected

数据库访问是有意纠缠在一起的，以表明从 SQLite 的角度来看，到同名内存数据库的两个连接是相同的。

引用资料:

1. SQLite URIs
2. SQLite shared cache

不幸的是，通过 URI 的连接仅在 Python 3.4 之后可用。但是，如果你有 Python 2.6 或更高版本(但不是 Python 3)，内置的 sqlite3 模块仍然能够导入 APSW 连接，可以用来达到同样的效果。这是插入式 sqlite3 模块替换:

from sqlite3 import *
from sqlite3 import connect as _connect
from apsw import Connection as _ApswConnection
from apsw import SQLITE_OPEN_READWRITE as _SQLITE_OPEN_READWRITE
from apsw import SQLITE_OPEN_CREATE as _SQLITE_OPEN_CREATE
from apsw import SQLITE_OPEN_URI as _SQLITE_OPEN_URI

# APSW and pysqlite use different instances of sqlite3 library, so initializing
# APSW won't help pysqlite. Because pysqlite does not expose any way to
# explicitly call sqlite3_initialize(), here goes an ugly hack. This only has
# to be done once per process.
_connect(':memory:').close()

def connect(database, timeout=5.0, detect_types=0, isolation_level=None,
            check_same_thread=True, factory=Connection, cached_statements=100,
            uri=False):
    flags = _SQLITE_OPEN_READWRITE | _SQLITE_OPEN_CREATE

    if uri:
        flags |= _SQLITE_OPEN_URI

    db = _ApswConnection(database, flags, None, cached_statements)
    conn = _connect(db, timeout, detect_types, isolation_level, 
                    check_same_thread, factory, cached_statements)

    return conn

关于python - 共享一个 :memory: database between different threads in python using sqlite3 package，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/3315046/