Aggregation query in mongo and spring-data-mongo - mongodb

Question

Hi everyone I have a big problem in querying my data. I have documents like this:
{
"_id" : NumberLong(999789748357864),
"text" : "#asd #weila #asd2 welcome in my house",
"date" : ISODate("2016-12-13T21:44:37.000Z"),
"dateString" : "2016-12-13",
"hashtags" : [
"asd",
"weila",
"asd2"
]
}
and I want to build two queries:
1) count for each day the number of hashtag and get out for example something like this:
{_id:"2016-12-13",
hashtags:[
{hashtag:"asd",count:20},
{hashtag:"weila",count:18},
{hashtag:"asd2",count:10},
....
]
}
{_id:"2016-12-14",
hashtags:[
{hashtag:"asd",count:18},
{hashtag:"asd2",count:14},
{hashtag:"weila",count:10},
....
]
}
2)another is the same but I want to set a period from 2016-12-13 to 2016-12-17.
For the first one I write this query and I get what I search but in Spring Data Mongo I don't know how to write.
db.comment.aggregate([
{$unwind:"$hashtags"},
{"$group":{
"_id":{
"date" : "$dateString",
"hashtag": "$hashtags"
},
"count":{"$sum":1}
}
},
{"$group":{
"_id": "$_id.date",
"hashtags": {
"$push": {
"hashtag": "$_id.hashtag",
"count": "$count"
}},
"count": { "$sum": "$count" }
}},
{"$sort": { count: -1}},
{"$unwind": "$hashtags"},
{"$sort": { "count": -1, "hashtags.count": -1}},
{"$group": {
"_id": "$_id",
"hashtags": { "$push": "$hashtags" },
"count": { "$first": "$count" }
}},
{$project:{name:1,hashtags: { $slice: ["$hashtags", 2 ]}}}
]);

Answer 1

You can still use a fraction of the same aggregation operation minus the pipeline steps after the second group stage but for the filtering aspect you'd have to introduce a date range query in an initial $match pipeline step.
The following mongo shell examples
show how you filter the aggregates for a particular date range:
1) Set a period from 2016-12-13 to 2016-12-14:
var startDate = new Date("2016-12-13");
startDate.setHours(0,0,0,0);
var endDate = new Date("2016-12-14");
endDate.setHours(23,59,59,999);
var pipeline = [
{
"$match": {
"date": { "$gte": startDate, "$lte": endDate }
}
}
{ "$unwind": "$hashtags" },
{
"$group": {
"_id": {
"date": "$dateString",
"hashtag": "$hashtags"
},
"count": { "$sum": 1 }
}
},
{
"$group": {
"_id": "$_id.date",
"hashtags": {
"$push": {
"hashtag": "$_id.hashtag",
"count": "$count"
}
}
}
}
]
db.comment.aggregate(pipeline)
2) Set a period from 2016-12-13 to 2016-12-17:
var startDate = new Date("2016-12-13");
startDate.setHours(0,0,0,0);
var endDate = new Date("2016-12-17");
endDate.setHours(23,59,59,999);
// run the same pipeline as above but with the date range query set as required
Spring Data Equivalent (untested):
import static org.springframework.data.mongodb.core.aggregation.Aggregation.*;
Aggregation agg = newAggregation(
match(Criteria.where("date").gte(startDate).lte(endDate)),
unwind("hashtags"),
group("dateString", "hashtags").count().as("count"),
group("_id.dateString")
.push(new BasicDBObject
("hashtag", "$_id.hashtags").append
("count", "$count")
).as("hashtags")
);
AggregationResults<Comment> results = mongoTemplate.aggregate(agg, Comment.class);
List<Comment> comments = results.getMappedResults();