I’m trying this code:
import sqlite connection = sqlite.connect('cache.db') cur = connection.cursor() cur.execute('''create table item (id integer primary key, itemno text unique, scancode text, descr text, price real)''') connection.commit() cur.close()
I’m catching this exception:
Traceback (most recent call last): File "cache_storage.py", line 7, in <module> scancode text, descr text, price real)''') File "/usr/lib/python2.6/dist-packages/sqlite/main.py", line 237, in execute self.con._begin() File "/usr/lib/python2.6/dist-packages/sqlite/main.py", line 503, in _begin self.db.execute("BEGIN") _sqlite.OperationalError: database is locked
Permissions for cache.db are ok. Any ideas?
I’m presuming you are actually using sqlite3 even though your code says otherwise. Here are some things to check:
$ fuser cache.dbshould say nothing)
$ sqlite3 cache.db "pragma integrity_check;"
$ sqlite3 cache.db ".backup cache.db.bak"
$ sqlite3 cache.db.bak ".schema"
The database is locked by another process that is writing to it. You have to wait until the other transaction is committed. See the documentation of connect()
One possible reason for the database being locked that I ran into with SQLite is when I tried to access a row that was being written by one app, and read by another at the same time. You may want to set a busy timeout in your SQLite wrapper that will spin and wait for the database to become free (in the original c++ api the function is sqlite3_busy_timeout). I found that 300ms was sufficient in most cases.
But I doubt this is the problem, based on your post. Try other recommendations first.
Oh, your traceback gave it away: you have a version conflict. You have installed some old version of sqlite in your local dist-packages directory when you already have sqlite3 included in your python2.6 distribution and don’t need and probably can’t use the old sqlite version. First try:
$ python -c "import sqlite3"
and if that doesn’t give you an error, uninstall your dist-package:
easy_install -mxN sqlite
import sqlite3 in your code instead and have fun.
Here’s a neat workaround for simultaneous access:
while True: connection = sqlite3.connect('user.db', timeout=1) cursor = connection.cursor() try: cursor.execute("SELECT * FROM queue;") result = cursor.fetchall() except sqlite3.OperationalError: print("database locked") num_users = len(result) # ...
Set the timeout parameter in your connect call, as in:
connection = sqlite.connect('cache.db', timeout=10)
Turned out the problem happened because the path to the db file was actually a samba mounted dir. I moved it and that started working.
I know this is old, but I’m still getting the problem and this is the first link on Google for it. OP said his issue was that the .db was sitting on a SMB share, which was exactly my situation. My ten minutes’ research indicates that this is a known conflict between sqlite3 and smb; I’ve found bug reports going back to 2007.
I resolved it by adding the “nobrl” option to my smb mount line in /etc/fstab, so that line now looks like this:
//SERVER/share /mnt/point cifs credentials=/path/to/.creds,sec=ntlm,nobrl 0 0
This option prevents your SMB client from sending byte range locks to the server. I’m not too up on my SMB protocol details, but I best I can tell this setting would mostly be of concern in a multi-user environment, where somebody else might be trying to write to the same db as you. For a home setup, at least, I think it’s safe enough.
My relevant versions:
In Linux you can do something similar, for example, if your locked file is development.db:
$ fuser development.db
This command will show which process is locking the file:
Just kill the process…
kill -9 5430
…And your database will be unlocked.
The reason mine was showing the “Lock” message was actually due to me having opened an SQLite3 IDE on my mac and that was the reason it was locked. I assume I was playing around with the DB within the IDE and hadn’t saved the changes and therefor a lock was placed.
Cut long story short, check that there are no unsaved changes on the db and also that it is not being used elsewhere.
I had the same problem:
As mentioned in many answers, the problem is that a connection has not been properly closed.
In my case I had
except blocks. I was accessing the database in the
try block and when an exception was raised I wanted to do something else in the
try: conn = sqlite3.connect(path) cur = conn.cursor() cur.execute('''INSERT INTO ...''') except: conn = sqlite3.connect(path) cur = conn.cursor() cur.execute('''DELETE FROM ...''') cur.execute('''INSERT INTO ...''')
However, when the exception was being raised the connection from the
try block had not been closed.
I solved it using
with statements inside the blocks.
try: with sqlite3.connect(path) as conn: cur = conn.cursor() cur.execute('''INSERT INTO ...''') except: with sqlite3.connect(path) as conn: cur = conn.cursor() cur.execute('''DELETE FROM ...''') cur.execute('''INSERT INTO ...''')
Because this is still the top Google hit for this problem, let me add a possible cause. If you’re editing your database structure and haven’t committed the changes, the database is locked until you commit or revert.
(Probably uncommon, but I’m developing an app so the code and database are both being developed at the same time)
cache.dbis being currently used by another process.
I also had this problem. I was trying to enter data into the database without saving changes I had made in it. after i saved the changes worked
You should check out if there is no DBMS administration and development platform working on your database (like pgAdmin), as this is probably the most popular cause of this error. If there is – commit the changes done and the problem is gone.
I had this problem while working with Pycharm and with a database that was originally given to me by another user.
So, this is how I solve it in my case:
in my case ,the error happened when a lot of concurrent process trying to read/write to the same table. I used retry to workaround the issue
def _retry_if_exception(exception): return isinstance(exception, Exception) @retry(retry_on_exception=_retry_if_exception, wait_random_min=1000, wait_random_max=5000, stop_max_attempt_number=5) def execute(cmd, commit=True): c.execute(cmd) c.conn.commit()
Even when I just had one writer and one reader, my issue was that one of the reads was taking too long: longer than the stipulated timeout of 5 seconds. So the writer timed out and caused the error.
So, be careful when reading all entries from a database especially from one which the size of the table grows over time.
I found this worked for my needs (thread locking):
conn = sqlite3.connect(database, timeout=10)
sqlite3.connect(database[, timeout, detect_types, isolation_level, check_same_thread, factory, cached_statements, uri])
When a database is accessed by multiple connections, and one of the processes modifies the database, the SQLite database is locked until that transaction is committed. The timeout parameter specifies how long the connection should wait for the lock to go away until raising an exception. The default for the timeout parameter is 5.0 (five seconds).
Easy solution: check once if you have opened the database in another window or in another terminal. That also locks your database. In my case, I closed all the other terminals that were locking the database (a terminal tab in Pycharm). Check each tab of the terminals of your IDE as well if there is a terminal that left the database open. exit() all the terminals should work unlocking the database.
in my case, the ‘locked’ message was happening due to the unsaved changes that I have done in DB BROWSER(SQL LITE), I had to save them then when I executed my script again, the problem was solved, hope this helps someone like in my case.
Just another possibility that happened to me, I was opening the database twice, the first opening blocked the second. Check that you are not doing that.
I am using sqlite3,I solve the block problem by adding the transaction isolation level