sqlite3_exec回调是同步还是异步？

Question

具有回调参数的Sqlite3函数sqlite3_exec()是同步还是异步运行？

示例电话:

int retStatus = sqlite3_exec(pDB, "SELECT * FROM SomeTable WHERE Something='Hi'", callback, &object, &error);

...Next line(s) of code...

• 同步:执行sqlite3_exec行,然后调用回调,然后执行下一行代码.

• Asynchonous:执行sqlite3_exec行,执行下一行代码,并在某个时刻调用回调.

Answer 1

同步.在代码继续之前找到的每一行都会调用回调:

static int _getName(void* pNames, int columns, char** data, char** columnNames)
{
    if (columns < 2)
    {
        assert(false && "Function called on wrong table!");
        // Signify failure
        return 1;
    }
    std::vector<std::string>* vNames = static_cast< std::vector<std::string>* >(pNames);
    vNames->push_back(data[1]);
    // Success:
    return 0;
}

{
    std::vector<std::string> names;
    // assume pDB is a valid, opened sqlite3* db
    char* error = 0;
    if (sqlite3_exec(pDB, "SELECT * FROM TableNames", _getName, static_cast<void*>(&names), &error) != SQLITE_OK)
    {
        // log and free error:
    }

    assert(names.size() && "No entries were found in the table");
}

_getName将在表格中的每个条目上调用TableNames.如果未找到任何条目,则不会调用该函数,也不会出现错误.如果你有一个名为TableNames的表有10个条目,那么names.size() == 10._getName如果返回非零,将不再被调用