![]() We can pass a simple Swift.String file path directly to the filename parameter in sqlite3_open(). Thankfully, Swift’s interoperability with C is pretty great. In C, it looks like int sqlite3_open(const char *filename, sqlite3 **ppDb), which translates to Swift as func sqlite3_open(_ filename: UnsafePointer!, _ ppDb: UnsafeMutablePointer!) -> Int32. The best place to start is opening a database with SQLite’s open function. Hiding these opaque types is my primary goal of wrapping SQLite in a Swift interface. ![]() SQLite’s C interface is exposed to Swift as a bunch of OpaquePointers and Int32 values. Plus, writing a wrapper around SQLite is pretty easy and gives us experience interacting with SQLite at a low level. I like to limit the dependencies I add to my apps and I’m very opinionated. As I mentioned in my previous article, there are already plenty of high-quality, open-source SQLite wrappers around, including GRDB and SQLite.swift. When it’s time to start implementing a real SQLite-based persistence layer for a Swift iOS or macOS app, one of the first things we’ll need to do is write a Swift wrapper around SQLite. Reacting to changes to data in the SQLite database.This is the second post in a series about powering modern apps with SQLite. \“addedDate is a required value.Building a lightweight SQLite wrapper in Swift Over time, we had to write multiple Core Data migrations which in rare cases failed with errors like the following: The Collect by WeTransfer contains a lot of data and uses Core Data as its storage. It could also be you ended up in this post because you already have a reason in which case I would love to hear more. I bet you wonder why you would want to force commit changes into the SQLite store. Reasons to force commit changes into the SQLite store Most database reader apps support WAL mode and automatically show changes that are not yet committed to the SQLite store. This could be caused by the fact that you’ve moved an SQLite file without its matching -wal and -shm file. In some cases, you might find yourself opening an SQLite database file realizing certain changes are missing. You can read the in-depth explanation regarding WAL mode if you like to learn more.Ĭore Data Changes not visible when opening a SQLite database file sqlite-shm file exists as the shared memory between multiple SQLite database connections and is used as an index for the WAL file. So-called “Checkpointing” eventually takes place to transfer all the transactions from the WAL file into the database. Commits finalizing data changes can actually happen in this WAL file which means that data can be saved while the original database stays untouched. ![]() The original content is preserved in the database file and new changes are added into the WAL file. The final commit saving the changes occurs when the rollback journal is deleted. New changes are written directly into the database file and the journal file is used to roll back changes in the case of a crash. Before WAL was introduced, SQLite was using the traditional rollback journal which works by keeping a copy of the original unchanged database content in the journal file. Journaling modes in Core Data and SQLite prevent data loss by writing new transactions in an in-between journal file. Write-Ahead Logging (WAL) results in multiple database files. In this blog post, I’ll give you both an example and an explanation of how you can do this. Because of this, you might want to force commit those changes into the SQLite store. This means that in some cases, changes are not yet visible in the SQLite store itself. With the WAL mode, Core Data keeps the main SQLite store file untouched and keeps track of data transactions in a -wal file within the same location of the SQLite store. The WAL mode is significantly faster in most scenarios compared to the previous default “rollback” journal mode and is the underlying reason that makes it possible to have concurrency in Core Data. Journaling in Core Data is best explained as the way data transactions are saved into the underlying SQLite store. Write-Ahead Logging is the default journaling mode for Core Data SQLite stores since iOS 7 and OS X Mavericks. 4 min read Write-Ahead Logging (WAL) disabled to force commits in Core Data.What to do when the delete journal mode is resulting in a dead lock.Verifying the configured journal mode using SQLite debugging.How to force commit changes into the SQLite database.Reasons to force commit changes into the SQLite store.
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