FMDB性能优化-使用事务提升性能

使用FMDB事务批量更新数据，速度会有大幅度提升。

下面的例子中可以看到，不使用事务，更新374条数据就用了6秒多；而使用事务，仅用了300多毫秒。（iPhone6测试）

不使用事务

FMDatabaseQueue * dbQueue = [SGVFoundationDataCenter shareInstance].dbQueue;    
[dbQueue inDatabase:^(FMDatabase *db) {
    // 清除数据
    NSLog(@"-- add Station begin count = %ld",stations.count);
    [db executeUpdate:@"delete from sgv_station where city_code = ?",@(cityCode)];
    [stations enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        SGVSubwayStation * station = obj;
        [db executeUpdate:@"INSERT INTO sgv_station (city_code, line_code, station_code, station_name, line_inner_code, is_wifi_valid) VALUES (?,?,?,?,?,?)",@(cityCode), @(station.lineCode),@(station.stationCode), station.stationName, @(station.lineInnerCode),@(station.isWiFiValid)];
    }];
    NSLog(@"-- add Station end"];
}];

使用事务

FMDatabaseQueue * dbQueue = [SGVFoundationDataCenter shareInstance].dbQueue;    
[dbQueue inDatabase:^(FMDatabase *db) {
    // 清除数据
    NSLog(@"-- add Station begin count = %ld",stations.count);
    [db beginTransaction];
    [db executeUpdate:@"delete from sgv_station where city_code = ?",@(cityCode)];
    [stations enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        SGVSubwayStation * station = obj;
        [db executeUpdate:@"INSERT INTO sgv_station (city_code, line_code, station_code, station_name, line_inner_code, is_wifi_valid) VALUES (?,?,?,?,?,?)",@(cityCode), @(station.lineCode),@(station.stationCode), station.stationName, @(station.lineInnerCode),@(station.isWiFiValid)];
    }];
    [db commit];
    NSLog(@"-- add Station end"];
}];