如何在 mongo 中使用 in 获取第一个元素?如果我有一个类似的列表['car', 'house', 'cat', dog']
,以及一个包含许多文档这些元素的集合,我想找到第一个包含 的文档cat
,以及第一个包含dog
等的文档。
我尝试过使用limit()
,但实际上它只给了我一个文档,可以是car
、 或dog
或cat
等。
有没有办法将限制与 $in 结合起来?
谢谢
编辑:我的数据示例:
{
"_id": {
"$oid": "51d53ace9e674607e837d62d"
},
"sensors": [{
"name": "os-hostname",
"value": "yahourt"
}, {
"name": "os-domain-name",
"value": ""
}, {
"name": "os-platform",
"value": "Win32NT"
}, {
"name": "os-fullname",
"value": "Microsoft Windows XP Professional"
}, {
"name": "os-version",
"value": "5.1.2600.131072"
}],
"type": "os",
"serial": "2_os_os-hostname_yahourt"
} {
"_id": {
"$oid": "51d53ace9e674607e837d62e"
},
"sensors": [{
"name": "cpu-id",
"value": "_Total"
}, {
"name": "cpu-usage",
"value": 37.2257042
}],
"type": "cpu",
"serial": "2_cpu_cpu-id_total"
} {
"_id": {
"$oid": "51d53ace9e674607e837d62f"
},
"sensors": [{
"name": "cpu-id",
"value": "0"
}, {
"name": "cpu-usage",
"value": 48.90282
}],
"type": "cpu",
"serial": "2_cpu_cpu-id_0"
} {
"_id": {
"$oid": "51d53ace9e674607e837d630"
},
"sensors": [{
"name": "cpu-id",
"value": "1"
}, {
"name": "cpu-usage",
"value": 25.54859
}],
"type": "cpu",
"serial": "2_cpu_cpu-id_1"
} {
"_id": {
"$oid": "51d53ace9e674607e837d631"
},
"sensors": [{
"name": "volume-name",
"value": "C:"
}, {
"name": "volume-label",
"value": ""
}, {
"name": "volume-total-size",
"value": "52427898880"
}, {
"name": "volume-total-free-space",
"value": "20305170432"
}, {
"name": "volume-percent-free-space",
"value": "38"
}, {
"name": "volume-reads-per-second",
"value": 0.0
}, {
"name": "volume-writes-per-second",
"value": 9.324152
}, {
"name": "volume-read-bytes-per-second",
"value": 0.0
}, {
"name": "volume-write-bytes-per-second",
"value": 194141.6
}, {
"name": "volume-queue-length",
"value": 0.0
}],
"type": "disk",
"serial": "2_disk_volume-name_c"
}