我应该如何构建我的MongoDB组件索引

Question

我有一个mongo图像元数据集合，由以下字段组成：camera_name(str(、photographer_name(str

我只想运行2个查询：

1. 给定camera_name，返回时间戳为<=的记录1639457261(UNIX时间戳示例(。记录必须按降序排序
2. 给定camera_name、photographer_name、分辨率、image_size和时间戳，我想检索记录，按输入的时间戳的降序排序

我创建了两个索引：

1. { "camera_name": 1, "timestamp": -1 }
2. { "camera_name": 1, "photographer_name": 1, "resolution": 1, "image_size": 1, "timestamp": -1}

第一个索引有效，但当我为第二个索引运行查询时，不会返回任何记录。我确信集合中存在记录，并且我希望在运行第二个查询时至少获得10条记录，但它返回了一个空列表。

索引的配置方式有问题吗？感谢

以下是示例数据：

{"camera_name": "Nikon", "photographer_name": "Aaron", "resolution": "1920x1080", "image_size": "3", "timestamp": 1397232415}
{"camera_name": "Nikon", "photographer_name": "Paul", "resolution": "1920x1080", "image_size": "4", "timestamp": 1717286853}
{"camera_name": "Nikon", "photographer_name": "Beth", "resolution": "720x480", "image_size": "1", "timestamp": 1503582086}
{"camera_name": "Nikon", "photographer_name": "Aaron", "resolution": "1920x1080", "image_size": "4", "timestamp": 1500628458}
{"camera_name": "Nikon", "photographer_name": "Paul", "resolution": "1920x1080", "image_size": "6", "timestamp": 1407580951}
{"camera_name": "Canon", "photographer_name": "Beth", "resolution": "1920x1080", "image_size": "5", "timestamp": 1166049453}
{"camera_name": "Canon", "photographer_name": "Paul", "resolution": "720x480", "image_size": "2", "timestamp": 1086317569}
{"camera_name": "Canon", "photographer_name": "Beth", "resolution": "720x480", "image_size": "1", "timestamp": 1400638926}
{"camera_name": "Canon", "photographer_name": "Aaron", "resolution": "720x480", "image_size": "1", "timestamp": 1345248762}
{"camera_name": "Canon", "photographer_name": "Paul", "resolution": "1920x1080", "image_size": "5", "timestamp": 1462360853}
{"camera_name": "Fuji", "photographer_name": "Beth", "resolution": "720x480", "image_size": "2", "timestamp": 1815298047}
{"camera_name": "Fuji", "photographer_name": "Shane", "resolution": "720x480", "image_size": "3", "timestamp": 1666493455}
{"camera_name": "Fuji", "photographer_name": "Beth", "resolution": "1920x1080", "image_size": "5", "timestamp": 1846677247}
{"camera_name": "Fuji", "photographer_name": "Beth", "resolution": "1920x1080", "image_size": "5", "timestamp": 1630996389}
{"camera_name": "Fuji", "photographer_name": "Shane", "resolution": "720x480", "image_size": "2", "timestamp": 1816829362}

我执行的查询：

1. camera_name=尼康和时间戳<1503582086应返回4条记录
2. camera_name='Fuji'，photographer_name='Beth'，分辨率='1920x1080'，image_size='5'，时间戳<190000000应该返回2条记录，但我得到了0条记录

Answer 1

索引不会"过滤器"；结果，它们允许您通过扫描索引树而不是扫描原始文档来更快地访问数据。

这意味着如果第二个查询"；"不返回任何内容"；，它与您构建的任何索引都无关，但您使用的实际查询与数据库中的任何文档都不匹配。

我还要提到的是，您的第二个索引可能会更小(取决于规模和数据分布等某些假设(，这可以帮助更新/插入性能，同时还可以减少存储大小。然而，从原始数据来看，我认为这些并不是你的紧急考虑因素。