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gh-135386: Fix "unable to open database file" errors on readonly DB #135566

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gh-135386: Fix "unable to open database file" errors on readonly DB #135566

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Fix: add immutable=1 flag for read-only SQLite access to avoid WAL/SH…
GeneralK1ng Jun 16, 2025
3e3a3ba
gh-135386: Fix dbm.sqlite3 readonly open error by using immutable=1
blurb-it[bot] Jun 16, 2025
7f988dd
Add test: readonly sqlite db without wal/shm (skip on Windows)
GeneralK1ng Jun 17, 2025
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16 changes: 11 additions & 5 deletions Lib/dbm/sqlite3.py
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Original file line number Diff line number Diff line change
Expand Up @@ -59,19 +59,25 @@ def __init__(self, path, /, *, flag, mode):

# We use the URI format when opening the database.
uri = _normalize_uri(path)
uri = f"{uri}?mode={flag}"
if flag == "ro":
# Add immutable=1 to allow read-only SQLite access even if wal/shm missing
uri = f"{uri}?mode={flag}&immutable=1"
else:
uri = f"{uri}?mode={flag}"
Comment on lines +62 to +66
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Suggested change
if flag == "ro":
# Add immutable=1 to allow read-only SQLite access even if wal/shm missing
uri = f"{uri}?mode={flag}&immutable=1"
else:
uri = f"{uri}?mode={flag}"
uri = f"{uri}?mode={flag}"
if flag == "ro":
# Add immutable=1 to allow read-only SQLite access even if wal/shm missing
uri += "&immutable=1"


try:
self._cx = sqlite3.connect(uri, autocommit=True, uri=True)
except sqlite3.Error as exc:
raise error(str(exc))

self._readonly = (flag == "ro")
# This is an optimization only; it's ok if it fails.
with suppress(sqlite3.OperationalError):
self._cx.execute("PRAGMA journal_mode = wal")
if not self._readonly:
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self._readonly is not used anywhere else, is it? You could just use flag != "ro" directly:

Suggested change
if not self._readonly:
if flag != "ro":

with suppress(sqlite3.OperationalError):
self._cx.execute("PRAGMA journal_mode = OFF")

if flag == "rwc":
self._execute(BUILD_TABLE)
if flag == "rwc":
self._execute(BUILD_TABLE)

def _execute(self, *args, **kwargs):
if not self._cx:
Expand Down
18 changes: 18 additions & 0 deletions Lib/test/test_dbm_sqlite3.py
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
import os
import sys
import unittest
from contextlib import closing
Expand Down Expand Up @@ -89,6 +90,23 @@ def test_readonly_keys(self):
def test_readonly_iter(self):
self.assertEqual([k for k in self.db], [b"key1", b"key2"])

@unittest.skipIf(sys.platform.startswith("win"), "incompatible with Windows file locking")
def test_readonly_open_without_wal_shm(self):
wal_path = self.filename + "-wal"
shm_path = self.filename + "-shm"

for suffix in wal_path, shm_path:
try:
os.remove(suffix)
except FileNotFoundError:
pass

os.chmod(self.filename, 0o444)

with dbm_sqlite3.open(self.filename, "r") as db:
self.assertEqual(db[b"key1"], b"value1")
self.assertEqual(db[b"key2"], b"value2")


class ReadWrite(_SQLiteDbmTests):

Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2025-06-16-15-00-13.gh-issue-135386.lNrxLc.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix :exc:`sqlite3.OperationalError` error when using :func:`dbm.open` with a read-only file object.
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