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Concurrency Safety

Before the version 1.2.2, sqllin-dsl can't ensure the concurrency safety. If you want to share a Database object between different threads, that would lead to unpredictable consequences. So, the best way is when you want to operate your database, create a Database object, and when you finish your operating, close it immediately.

But, that's very inconvenient, we always have to create a database connection and close it frequently, this is a waste of resources. For example, if we are developing an Android app, and in a single page (Activity/Fragment), we hope we can keep a Database object, when we want to operate the database in background threads (or coroutines), just use it, and, close it in certain lifecycle functions (onDestroy, onStop, etc.).

At that time, we should make sure the concurrency safety that we share the Database object between different threads (or coroutines). So, start with the version 1.2.2, we can use the new API Database#suspendedScope to replace the usage of database {}. For example, if we have some old code:

fun sample() {
    database {
        PersonTable { table ->
            table INSERT Person(age = 4, name = "Tom")
            table INSERT listOf(
                Person(age = 10, name = "Nick"),
                Person(age = 3, name = "Jerry"),
                Person(age = 8, name = "Jack"),
            )
        }
    }
}

We use the new API Database#suspendedScope to replace the database {}, it will be like that:

fun sample() {
    database suspendScope {
        PersonTable { table ->
            table INSERT Person(age = 4, name = "Tom")
            table INSERT listOf(
                Person(age = 10, name = "Nick"),
                Person(age = 3, name = "Jerry"),
                Person(age = 8, name = "Jack"),
            )
        }
    }
}

The suspendedScope is a suspend function. Inside the suspendedScope, the all operations are atomic. That means: If you share the same Database object between two coroutines, it can ensure the suspendedScope executing later will wait for the one executing earlier to finish.

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