Spring data MongoDb query based on last element of nested array field - mongodb

Question

I have the following data (Cars):
[
{
"make" : “Ferrari”,
"model" : “F40",
"services" : [
{
"type" : "FULL",
“date_time" : ISODate("2019-10-31T09:00:00.000Z"),
},
{
"type" : "FULL",
"scheduled_date_time" : ISODate("2019-11-04T09:00:00.000Z"),
}
],
},
{
"make" : "BMW",
"model" : “M3",
"services" : [
{
"type" : "FULL",
"scheduled_date_time" : ISODate("2019-10-31T09:00:00.000Z"),
},
{
"type" : "FULL",
“scheduled_date_time" : ISODate("2019-11-04T09:00:00.000Z"),
}
],
}
]
Using Spring data MongoDb I would like a query to retrieve all the Cars where the scheduled_date_time of the last item in the services array is in-between a certain date range.
A query which I used previously when using the first item in the services array is like:
mongoTemplate.find(Query.query(
where("services.0.scheduled_date_time").gte(fromDate)
.andOperator(
where("services.0.scheduled_date_time").lt(toDate))),
Car.class);
Note the 0 index since it's first one as opposed to the last one (for my current requirement).
I thought using an aggregate along with a projection and .arrayElementAt(-1) would do the trick but I haven't quite got it to work. My current effort is:
Aggregation agg = newAggregation(
project().and("services").arrayElementAt(-1).as("currentService"),
match(where("currentService.scheduled_date_time").gte(fromDate)
.andOperator(where("currentService.scheduled_date_time").lt(toDate)))
);
AggregationResults<Car> results = mongoTemplate.aggregate(agg, Car.class, Car.class);
return results.getMappedResults();
Any help suggestions appreciated.
Thanks,

Answer 1

This mongo aggregation retrieves all the Cars where the scheduled_date_time of the last item in the services array is in-between a specific date range.
[{
$addFields: {
last: {
$arrayElemAt: [
'$services',
-1
]
}
}
}, {
$match: {
'last.scheduled_date_time': {
$gte: ISODate('2019-10-26T04:06:27.307Z'),
$lt: ISODate('2019-12-15T04:06:27.319Z')
}
}
}]
I was trying to write it in spring-data-mongodb without luck.
They do not support $addFields yet, see here.
Since version 2.2.0 RELEASE spring-data-mongodb includes the Aggregation Repository Methods
The above query should be
interface CarRepository extends MongoRepository<Car, String> {
#Aggregation(pipeline = {
"{ $addFields : { last:{ $arrayElemAt: [$services,-1] }} }",
"{ $match: { 'last.scheduled_date_time' : { $gte : '$?0', $lt: '$?1' } } }"
})
List<Car> getCarsWithLastServiceDateBetween(LocalDateTime start, LocalDateTime end);
}
This method logs this query
[{ "$addFields" : { "last" : { "$arrayElemAt" : ["$services", -1]}}}, { "$match" : { "last.scheduled_date_time" : { "$gte" : "$2019-11-03T03:00:00Z", "$lt" : "$2019-11-05T03:00:00Z"}}}]
The date parameters are not parsing correctly. I didn't spend much time making it work.
If you want the Car Ids this could work.
public List<String> getCarsIdWithServicesDateBetween(LocalDateTime start, LocalDateTime end) {
return template.aggregate(newAggregation(
unwind("services"),
group("id").last("services.date").as("date"),
match(where("date").gte(start).lt(end))
), Car.class, Car.class)
.getMappedResults().stream()
.map(Car::getId)
.collect(Collectors.toList());
}
Query Log
[{ "$unwind" : "$services"}, { "$group" : { "_id" : "$_id", "date" : { "$last" : "$services.scheduled_date_time"}}}, { "$match" : { "date" : { "$gte" : { "$date" : 1572750000000}, "$lt" : { "$date" : 1572922800000}}}}]