在 iOS 5 上设置 sqlite config SQLITE_CONFIG_SERIALIZED 返回

问题描述

随着 iOS 5 的发布，我们在为 sqlite 数据库设置序列化选项时遇到越来越多的错误(因此它的保存用于多线程).我们在 sqlite3_config 上收到 SQLITE_MISUSE 错误代码.有人注意到这种奇怪的行为吗?有人知道我该如何解决这个问题吗?它在以前的 iOS 版本上运行良好.

With the release of iOS 5 we are getting more and more errors when setting the serialized option for the sqlite database (so its save to be used for multithreading). We are getting SQLITE_MISUSE error code on sqlite3_config. Has someone noticed this odd behavior? And does someone know how I can fix this? It works perfectly fine on previous iOS versions.

代码如下:

- (sqlite3 *)getNewDBConnection {
    NSLog(@"sqlite3 lib version: %s", sqlite3_libversion());

    //sqlite3_config() has to be called before any sqlite3_open calls.

    if (sqlite3_threadsafe() > 0) {
        int retCode = sqlite3_config(SQLITE_CONFIG_SERIALIZED);
        if (retCode == SQLITE_OK) {
            NSLog(@"Can now use sqlite on multiple threads, using the same connection");
        } else {
            NSLog(@"setting sqlite thread safe mode to serialized failed!!! return code: %d", retCode);
        }
    } else {
        NSLog(@"Your SQLite database is not compiled to be threadsafe.");
    }

    sqlite3 *newDBconnection;

    // Open the database
    if (sqlite3_open([[self getDatabaseFilePath] UTF8String], &newDBconnection) == SQLITE_OK) {
        NSLog(@"Database Successfully Opened :)");
    } else {
        sqlite3_close(newDBconnection);
        NSLog(@"Error in opening database :(");
    }

    return newDBconnection; 
}

这是输出:

sqlite3 lib version: 3.7.7
setting sqlite thread safe mode to serialized failed!!! return code: 21
Database Successfully Opened :)

推荐答案

我也为此苦苦挣扎，终于找到了解决方案.

I struggled long and hard with this as well and finally got the solution.

正如@enobufs 所说，sqlite3_config() 需要在sqlite3_initialize() 之前调用.但是，操作系统可能会为我们初始化 SQLite，所以我还在 sqlite3_config() 之前做了一个 sqlite3_shutdown().

As @enobufs said, sqlite3_config() needs to be called before sqlite3_initialize(). However, the OS might initialize SQLite for us so I also do a sqlite3_shutdown() before the sqlite3_config().

1. sqlite3_shutdown()
2. sqlite3_config()
3. sqlite3_initialize().

然后它还需要为每个查询使用相同的连接，因为它是对被序列化的数据库连接的访问​​.如此处所述 http://www.sqlite.org/capi3ref.html#sqliteconfigserialized

Then its also necessary to use the same connection for every query as it is the access to the database connection that gets serialized. As described here http://www.sqlite.org/capi3ref.html#sqliteconfigserialized

因此，我会在应用启动后立即创建一个连接，并将该连接传递给每个需要它的类.

So I create a connection as soon as the app starts up and the pass that connection to every class that needs it.

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