[英]Advanced mongoDB query in Matlab using mongo-java-driver
[英]implementing mongodb query in java using java mongo driver
我正在使用下面的mongo查询来获取最高温度。 谁能帮助使用BasicDBObject
和DBObject
使用mongo Java驱动程序在Java中实现?
db.EventLog.aggregate(
[
{
$group:
{
_id: "$_id",
maxInnerTemp: { $max: { $concat : [ "0", "$fields.innerTemp"]}}
}
}
]
)
使用mongo java聚合,例如以下代码(未经测试):
// $group operation
BasicDBList concat = new BasicDBList();
concat.add("0");
concat.add("$fields.innerTemp");
DBObject groupFields = new BasicDBObject("_id", "$_id");
groupFields.put("maxInnerTemp", new BasicDBObject("$max", new BasicDBObject("$concat", concat));
DBObject group = new BasicDBObject("$group", groupFields);
// run aggregation
List < DBObject > pipeline = Arrays.asList(group); AggregationOutput output = collectionName.aggregate(pipeline);
for (DBObject result: output.results()) {
System.out.println(result);
}
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