You could just check for file existence and then create it. A race condition is exceedingly rare. If another program already created it, why does that matter? After all, the file is now there for you to use, and you can handle any races between two processes inside that file. Why are you checking if the database exists at all? You do not care if the database exists or not. You only care that you can open it.
You should be opening it and then checking to see if it contains what you expect it to contain, and if it does not, THEN you initialize the database. Both will then be free to use the DB in the normal fashion. In the " copies trying to initialize at the same time", I think there is a good chance that none of them manage to successfully set WAL mode and clear the flag.
Another approach would be to treat empty files as unusable, and do my initialization only for new files initialize to a temporary file name, and then rename to the user-requested file name. That means I have to close the temporary file, rename it assumes rename fails if the target exists , and then open it again.
With this approach, exactly one of the initializers succeed. That has its own set of problems sqlite3. If you get here, then you have exclusive access to the database so that you can do your initialization after which you do:.
The key answer to how to handle races is how databases normally handle races, using a Transaction. If the program places the check and the creation of the tables and such in a transaction, you won't have the race problem. If you use a simple BEGIN, then the second one might see the tables not there when it checks but will get a BUSY return when it goes to create the tables, and that tells it it needs to back off and start over.
This makes the logic simpler, but if the database in use might have longish write transactions might get some delays on start that wouldn't be otherwise needed. At least in my case, it is unlikely that any harm would come due to a rogue process in between steps 1 and 2 although it is not certain. I fail to see why passing that flag shouldn't be allowed; I don't know if there is some internal condition in SQLite that somehow won't work as it is currently written.
However, it could probably be corrected; if it needs to mask out the flag after it opens the database file at first in case it needs to use it again for some reason that I don't know , then it might do so. I don't know what other considerations there might be or even if this is one of them. Why not just open the file with the desired flags, save the result, and then do the SQLite open? Of course, you still have to have the same transaction to initialize the database in the case of a new file to deal with the same ultimate race conditions.
You might, for example, create a crc32 aggregate function. After all, what harm could come from some other process creating a file in between checking if it already exists and actually performing the open?
Then, someone and I can't find the link to the story right now, sorry demonstrated that this race condition opened up a security hole. Skip to content. Report a Bug. Previous Prev. Next Continue.
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Visit chat. SQLite Viewer is the correct option to perform this task. It helps users to easily open and view SQLite data file in the Windows operating system. Also, The tool is displayed in a simplified interface that makes it easier for the non-technical user to view SQLite database files.
The software allows you to view deleted data from the SQLite database. The software allows a separate tab to analyze deleted records from the SQLite database file more efficiently.
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