从 sqlite3 远程数据库读取 [英] Reading from sqlite3 remote databases

问题描述

在我的服务器中，我试图从一堆 sqlite3 数据库(从 Web 客户端发送)中读取数据并处理它们的数据.db 文件位于 S3 存储桶中，我有它们的 url，我可以在内存中打开它们.

In my server I'm trying to read from a bunch of sqlite3 databases (sent from web clients) and process their data. The db files are in an S3 bucket and I have their url and I can open them in memory.

现在的问题是 sqlite3.connect 只接受一个绝对路径字符串，我无法将内存中的文件传递给它.

Now the problem is sqlite3.connect only takes an absolute path string and I can't pass to it a file in memory.

conn=sqlite3.connect() #how to pass file in memory or url
c=conn.cursor()
c.execute('''select * from data;''')
res=c.fetchall()
# other processing with res

推荐答案

SQLite 要求 数据库文件存储在磁盘上(它使用各种锁和分页技术).内存文件是不够的.

SQLite requires database files to be stored on disk (it uses various locks and paging techniques). An in-memory file will not suffice.

我会创建一个临时目录来保存数据库文件，将其写入该目录，然后连接到它.该目录也为 SQLite 提供了写入提交日志的空间.

I'd create a temporary directory to hold the database file, write it to that directory, then connect to it. The directory gives SQLite the space to write commit logs as well.

为了处理这一切，上下文管理器可能会有所帮助:

To handle all this, a context manager might be helpful:

import os.path
import shutil
import sqlite3
import sys
import tempfile

from contextlib import contextmanager


@contextmanager
def sqlite_database(inmemory_data):
    path = tempfile.mkdtemp()
    with open(os.path.join(path, 'sqlite.db'), 'wb') as dbfile:
        dbfile.write(inmemory_data)
    conn = None
    try:
        conn = sqlite3.connect(os.path.join(path, 'sqlite.db'))
        yield conn
    finally:
        if conn is not None:
            conn.close()
        try:
            shutil.rmtree(path)
        except IOError:
            sys.stderr.write('Failed to clean up temp dir {}'.format(path))

并将其用作:

with sqlite_database(yourdata) as connection:
    # query the database 

这会将内存中的数据写入磁盘，打开一个连接，让您使用该连接，然后在您之后进行清理.

This writes in-memory data to disk, opens a connection, lets you use that connection, and afterwards cleans up after you.

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