I'm using core data and am pre-populating it using a SQlite database that I provide in the bundle. It's been working fine for a while, however I've just edited the database and when I copy it over there is no data displayed. So I opened the database that is on the ios simulator, in base, and I found an sqlitemaster table that contains lots of SQL statements such as CREATE TABLE..., but the tables I want don't contain any data.
What's weirder is that after a while the database is fine and all the data is in it as normal. Is this because the statements in the sqlitemaster table were executed?
Has this happened to anybody else? I don't know whether it's because I've upgraded to iOS 7 or not? If anybody could point me in the right direction that would be great
The latest iOS Core Data SQLite backend uses journaling. You should notice .shm and .wal files in the same directory as what you assumed was your main sqlite backing store for Core Data. This data eventually gets into the main file, but journaling optimizes some situations for Core Data configured with SQLite.
As a developer, you generally never care about this from within the app, but if you are trying to inspect the persisted Core Data graph via the actual file, you'll need to be aware.
I've had a look around and the journaling was causing it to go all weird. Found this post which shows the same problem I had. If anyone else has this look at that post
Related
I am having problem reading a file. I'm using MagicalRecord as my CoreData wrapper. I successfully save or update object. With my NSLog I can see it, everything is fine and I can use it in my database. But every time I want to see SQLite file with my application (I'm using Datum LE), file is empty. I cannot access that file directly within my Library folder in my app. I copy that file to my desktop and it is empty. What am I doing wrong? So once more, everything inside my iOS application works fine, I can see records being saved and I can fetch them normally.
You are clearly looking at the wrong file. If your app is saving (I assume, across app restarts), the date is definitely saved.
One way to find out is to NSLog the persistent store URL and check the referenced file.
I believe the issue you are encountering is the new default journaling mode that Core Data uses.
See this article
https://developer.apple.com/library/ios/qa/qa1809/_index.html
Basically your changes are not written to the .sqlite file, but are found in .sqlite-wal. HOWEVER, most SQLite reading apps I have tried blow away the -wal when you open the .sqlite, so good luck.
You could try changing the journaling mode for debugging purposes
I have app in that i am using coredata. And when i install the app three files are getting created in the document directory called “test.sqlite, test.sqlite-shm and test.sqlite-wal". And now in second app i copy the test.sqlite in the folder and i want to access the database and tables but i got error like this "no such table found". Is there any issue that i create the database with coredata? please help me.
You either need to:
send all of the sqlite* files that Core Data creates
export the content from the data store, format it and send that
Option 1 should work and be fast to implement, but it isn't very future proof. Option 2 will take longer but is a much better solution.
My app is using Core Data framework with storage type of sqlite . I received several feedback commenting that user data stored in Core Data is lost, it seems the sqlite file read fail. After i got the sqlite files from user, there are 3 files (.sqlite, .sqlite-wal, .sqlite-shm).
But only empty results can be queried in these sqlite files.
What I got from the users is they may power off their iPhone while the app is active.
I just noticed Core Data begin use WAL as the default journal_mode in ios7, while it's default as DELETE prior to ios7. I didn't set up the journal_mode manually in my code.
I'm not sure what is the root cause of this issue. But data lost is unacceptable to users anyway. Did anyone happen to meet this issue before?
Should I set up the journal_mode to DELETE manually for all iOS version?
Thank you!
Update：
User reported it works normally on previous day, but then everything is lost on next day.
i have submitted an app on the app store that uses core data.
The problem is that i duplicated my project and then lost the first source code. If i update the app using the "duplicated" source code does it delete all core datas users may have stored? i know that if you change the file file-xcdatamodel without mapping the previous datas you will lose all you had stored, can i assume the duplicated project use the exact same file?
thanks in advance
In that case I think that, if you didn't modify your xcdatamodel, the data stored by user will keep during the upgrade. In order to be sure, you can install your own apo from App Store, save some data, update this app from Xcode with your new version and check if the stored data still are there.
If you've modify your xcdatamodel, you must perform a light or a heavy migration, depending on your canges.
I have the task to re-engineer an iPhone app which makes use of Core Data to store some values. Unfortunately I do not have access to the original source code but I do have acces to old database files, copied directly from the device where the old version of the app is installed.
I have to create a new version of the app with some new functionality and I am trying to import the data from the Sqlite Db and migrate it to a new version.
I am already failing at the task to read the data from the old database. Though I can open the Sqlite file and such was able to exactly reproduce the data structure in my own datamodel, everytime I try to read the data, it fails with a
Can't find model for source store
error.
Ignoring the old data is not an option because there is important data stored there.
I googled for solutions and tried every recommended solution related to migrating data but it all fails. Maybe I can not use the Sqlite created by another app? Or so I overlook something in re-engineering the structure of the datamodel even when I used exactly the some field names and datatypes? Is there another way around this?
I could not solve the issue but I found a workaround. By using Sqlite directly, I was able to query the legacy data and import it into my newly created data model. A good starter point for using Sqlite is here:
http://www.techotopia.com/index.php/IOS_4_iPhone_Database_Implementation_using_SQLite