النسخ الاحتياطي والاستعادة وأدلة السلامة

import sqlite3
from contextlib import closing

with closing(sqlite3.connect(":memory:", isolation_level=None)) as source, \
     closing(sqlite3.connect(":memory:", isolation_level=None)) as copy:
    source.executescript("CREATE TABLE item(value INTEGER); INSERT INTO item VALUES(2);")
    source.backup(copy)
    source.execute("UPDATE item SET value=99")
    print("source", source.execute("SELECT value FROM item").fetchone()[0])
    print("copy", copy.execute("SELECT value FROM item").fetchone()[0])

source 99
copy 2

تحفظ النسخة المكتملة 2 رغم تغير المصدر إلى 99. القاعدتان خاصتان وتغلقان.

import sqlite3
from pathlib import Path
from tempfile import TemporaryDirectory
from contextlib import closing

with TemporaryDirectory(prefix="sqlite-backup-training-") as temporary:
    folder = Path(temporary)
    with closing(sqlite3.connect(folder / "source.db", isolation_level=None)) as source, \
         closing(sqlite3.connect(folder / "backup.db", isolation_level=None)) as backup, \
         closing(sqlite3.connect(":memory:", isolation_level=None)) as restored:
        source.executescript("CREATE TABLE account(id INTEGER PRIMARY KEY,amount INTEGER); INSERT INTO account VALUES(1,42);")
        source.backup(backup)
        print("backup_check", backup.execute("PRAGMA integrity_check").fetchone()[0])
        backup.backup(restored)
        print("restored", restored.execute("SELECT amount FROM account WHERE id=1").fetchone()[0])
        print("foreign_key_issues", len(restored.execute("PRAGMA foreign_key_check").fetchall()))

backup_check ok
restored 42
foreign_key_issues 0

تنجح النسخة في فحص السلامة المصطنع؛ وتحوي المستعادة 42 ولا تبلغ عن مخالفة مفاتيح أجنبية.