I'm creating a database "UserDataBase.db" and while opening this in SQLite browser neither data nor tables is being shown if I am doing any CRUD operations then it works.I am providing images link also regarding which file I am locating in SQLite browser.First I am synchronizing these files and saving on Desktop and opening in SQLite browser.I have tried to fetch the data from the database it works fine.
As the database is just 4k and that the -wal file is 80.5k the data hasn't been written/comitted. You need to close the database or checkpoint the database and then copy the file. Or you could copy the -wal and -shm files into DB Browser open it and then close it and then re-open it.
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I have a Flutter/Dart application that I am coding using Android Studio. I use a database called envirodatabase.db with the sqflite package. I want to open the database in DB Browser for SQLite on my computer, but the only way it lets me do that is through saving a copy of the file, not the file itself.
How do I open the original file in DB Browser for SQLite?
Here is my Device File Explorer
What I tried doing was I right clicked > Save As in the Device File Explorer where my app's database was. I saved it to my desktop and opened it, but the changes don't update the original file.
Similar questions with different problems:
Viewing sqlite database file using DB browser for SQlite
Android Studio saves files you open this way in a temporary directory outside of your project. If you make modifications to a file you opened using the Device File Explorer, and would like to save your changes back to the device, you must manually upload the modified version of the file to the device.
https://developer.android.com/studio/debug/device-file-explorer
What I had to do was, back in the Device File Explorer, after saving to Desktop and making changes,
Right click the folder
Click Upload
Select the file with the database changes
(Not sure if this is needed but I did it just to be safe) Right click the folder or file and click synchronize
Hot restart the application (hot reload may also work, but again, just to be safe).
I downloaded and installed the SQLite ODBC Driver from http://ch-werner.de/sqliteodbc/. Works great with one issue. I can't seem to get an exclusive lock if another app has the database open.
I'm using a CAD application called Altium. I'm trying to build a prototype parts database in SQLITE to house data. I installed the ODBC driver referenced above and I can get to the data just fine. The issue is if I try to open the same database in an app like SQLITEStudio or DB Browser for SQLITE I can never get an exclusive lock to write new records. Altium never closes its connection and I don't know if that's the problem or not.
When I read https://www.sqlite.org/lockingv3.html it seems to indicate that multiple processes would need to communicate in order for one to obtain an exclusive lock (necessary for a write). This leads me to believe my issue is the first app never releasing it's shared lock so the second app can never get an exclusive lock. Am I interpreting this correctly?
I'm experiencing the same difficulties with SQLite as an Altium database. The database file can't be updated while Altium is open and had created a connection to the database. There are two workarounds I've found so far:
Enable Write Ahead Logging style database journal
The default database journal style, DELETE, creates a copy of the database, temporarily, writes to the database file, and, when the write is verified, deletes the temporary copy.
Write ahead logging, WAL, puts all changes in a temporary file while leaving the original copy of the database alone. Processes accessing the database parse the database file and the WAL temporary files, and return information reflecting all changes. I can confirm that writes outside of Altium are seen when doing a database refresh within Altium.
The writes stored in the WAL file are written to the original database when a checkpoint operation happens. Either when a process calls PRAGMA wal_checkpoint; or after a number of operations specified by the WAL Auto Checkpoint setting.
You can enable WAL journal mode in DB Browser's Edit Pragmas tab:
DB Browser Database Settings
The problem still isn't fixed, though. Checkpointing the database doesn't work while Altium is open. The database file is still locked from changes.
The caveat for us is that we want to backup and maintain a history of the database file in Git (yes, this is not a recommended use of Git). Writes to the journal files aren't tracked in Git, which doesn't see a change in the database file until it is checkpointed. This means that we can't push or pull from Git while Altium is open. We could track the database and journal files, but the other consequence is that a simple checkpoint with no data changes will be seen by Git as a change.
Use an alternative ODBC driver
I tested an alternative, proprietary ODBC driver from devart. When I configure Altium to connect to the SQLite database using the devart driver, DB Browser has no problems writing to the file while Altium is open, regardless of journal settings. Altium can also see those changes with a refresh operation.
Conclusion
Christian Werner's ODBC driver (as of version 0.9996) is locking the file in a manner that the devart driver does not, even while Atlium maintains a connection to the database through the driver. WAL journal mode can be a workaround for some situations.
If a SQLite database using write-ahead logging is interrupted with un-checkpointed transactions (due to a power failure or whatever), then reopened with the temporary -wal file missing, will the database open cleanly to its state as of the last checkpoint, or will it be corrupted in some way?
We're trying to get SQLite working with iCloud (yes, we know you're not supposed to do that, but we also make a Windows and an Android app and need a cross-platform database solution), and we think that WAL provides a potential way to avoid having to maintain two copies of our database - we'd keep the -wal file outside of iCloud but store the main database in it, thus avoiding the problem of iCloud backing up rollback journals (or backing up databases mid-transaction without those journals).
The file format documentation mentions a "hot WAL file", but this applies only to uncommitted data.
The database file itself does not contain any information about committed data in the -wal file, i.e., transactions before a checkpoint typically do not alter the main database file at all.
Therefore, deleting the -wal file will simply restore the database to the state it was after the last checkpoint (which is outdated, but consistent); all transactions committed later will just be lost.
See the "Checkpointing" section of SQLite's Write-Ahead Logging. From what I understand, the data in the WAL file would simply not be committed.
In other words, you'd lose the data in the .WAL file that hasn't yet been committed, but the main database itself should be perfectly fine.
It can lead to db corruption when WAL file would be deleted during checkpointing operation. In case of unfinished db modification WAL file is necessary to complete the changes, otherwise db file is in transient state. DB and WAL file create complete picture of the db state. It is also explicitly stated in https://www.sqlite.org/howtocorrupt.html#delhotjrnl that "SQLite must see the journal files in order to recover from a crash or power failure."
I want to know why SQLite create two file inside the path.and what is the diffrence these files.
I have a database name mydatabase.
when i see in given path there are two files.
data/data/pack name/databases/....
1- mydatabase
2- mydatabase-journal
mydatabase is main database file, which contains everything about that database.
mydatabase-journal is journal file. It does not exist by default, and only gets created by SQLite when necessary to keep intent log of what SQLite wants to do with database. Basically, this is intent of what should be done to main database file after transaction is properly finished. If you finish all transactions normally and disconnect from database gracefully, -journal file will be normally removed automatically.
If disconnect was abrupt - like process killed or crashed, -journal file will remain and should NOT be deleted. When next time SQLite opens this database once again, it will notice presence of -journal file and will replay or rollback unfinished transactions, such that main database file is consistent and not corrupted.
If you remove -journal file manually, recovery is not guaranteed and database may be completely corrupted - so, DO NOT remove -journal files.
Probably easiest way to properly get rid of -journal files is to do this command:
sqlite3 mysqlitedatabase.db VACUUM
It will VACUUM (optimize) your database and should leave only main file as a result.
I've got a sqlite3 DB that I need to read (not write) sitting on a read-only filesystem. There is also a -journal file associated with the database, which is interfering with opening the database because the first thing the sqlite code wants to do is delete that -journal file and it cannot because the filesystem is read-only. Setting the journal_mode to off doesn't help because that apparently only applies to new transactions. Is there a way to tell sqlite3 to simply ignore all mention of a -journal file associated with a DB?
Unfortunately no.
The problem is that the existence of a journal file indicates that a transaction was left in an incomplete state, and needs to be rolled back by transferring the content of the journal file back into the database file.
This requires write access to the file system, and SQLite will not allow you to open the file without performing this rollback.
You can read more about this here: Read-Only Databases:
No SQLite database (regardless of whether or not it is WAL mode) is readable if it is located on read-only media and it requires recovery. So, for example, if an application crashes and leaves an SQLite database with a hot journal, that database cannot be opened unless the opening process has write privilege on the database file, the directory containing the database file, and the hot journal. This is because the incomplete transaction left over from the crash must be rolled back prior to reading the database and that rollback cannot occur without write permission on all files and the directory containing them.
If you don't care about the possible corruption that discarding the journal file might lead to, you can make a copy of the database file, and leave the journal behind. Though, if you have the ability to do that, I would in fact copy the journal file too, to a writable file system, and open that database as normal, which would roll back the transaction properly.
The copy on the read-only file system though is not usable in its current state.