Java 返回唯一的mongo文档

我有一个收藏。以下是示例文档

{
"bannerUserSessionId" : "565269c7d52ece855050b3b7bd4ae8d6f52161871394e2d312c340a086f93314",
"bannerId" : "<String> kitchen-chimneys||1488286849020|HP|PromoBanner4",
"bannerEventLabel" : "<String> kitchen-chimneys",
"bannerPage" : "HP",
"bannerWidget" : "PromoBanner4",
"bannerClickTimestamp" : "Mar 04, 2017 15:05:56 PM"
}
{
"bannerUserSessionId" : "565269c7d52ece855050b3b7bd4ae8d6f52161871394e2d312c340a086f93314",
"bannerId" : "<String> kitchen-   chimneys||1488286849020|HP|PromoBanner4",
"bannerEventLabel" : "<String> kitchen-chimneys",
"bannerPage" : "HP",
"bannerWidget" : "PromoBanner4",
"bannerClickTimestamp" : "Mar 04, 2017 15:06:19 PM"
}

有没有可能以这样一种方式查询mongodb，即我将得到唯一的文档，因为上述两个文档除了不同的timestamp对象之外是相同的

---

因此，我只需要一条记录。

您可以按键选择

$group

，然后选择

$first

时间戳值

db.collection.aggregate([{
    $group: {
        _id: {
            "bannerUserSessionId": "$bannerUserSessionId",
            "bannerId": "$bannerId",
            "bannerEventLabel": "$bannerEventLabel",
            "bannerPage": "$bannerPage"
        },
        "bannerClickTimestamp": {
            $first: "$bannerClickTimestamp"
        }
    }
}])