How to compare two collections and archive documents which are not common - mongodb

Question

I have two collections for example CollectionA and CollectionB both have common filed which is hostname
Collection A :
{
"hostname": "vm01",
"id": "1",
"status": "online",
}
Collection B
{
"hostname": "vm01",
"id": "string",
"installedversion": "string",
}
{
"hostname": "vm02",
"id": "string",
"installedversion": "string",
}
what i want to achieve is when i receive a post message for collection B
I want to check if the record exists in Collection B based on hostname and update all the values. if not insert the new record ( i have read it can be achieved by using upsert -- still looking how to make it work)
I want to check if the hostname is present in Collection A , if not move the record from collection B to another collection which is collection C ( as archive records).ie in the above hostname=vm02 record from collection B should be moved to collectionC
how can i achieve this using springboot mongodb anyhelp is appreciated.The code which i have to save the Collection B is as follows which i want to update to achieve the above desired result
public RscInstalltionStatusDTO save(RscInstalltionStatusDTO rscInstalltionStatusDTO) {
log.debug("Request to save RscInstalltionStatus : {}", rscInstalltionStatusDTO);
RscInstalltionStatus rscInstalltionStatus = rscInstalltionStatusMapper.toEntity(rscInstalltionStatusDTO);
rscInstalltionStatus = rscInstalltionStatusRepository.save(rscInstalltionStatus);
return rscInstalltionStatusMapper.toDto(rscInstalltionStatus);
}
Update 1 : The below works as i expected but I think there should be a better way to do this.
public RscInstalltionStatusDTO save(RscInstalltionStatusDTO rscInstalltionStatusDTO) {
log.debug("Request to save RscInstalltionStatus : {}", rscInstalltionStatusDTO);
RscInstalltionStatus rscInstalltionStatus = rscInstalltionStatusMapper.toEntity(rscInstalltionStatusDTO);
System.out.print(rscInstalltionStatus.getHostname());
Query query = new Query(Criteria.where("hostname").is(rscInstalltionStatus.getHostname()));
Update update = new Update();
update.set("configdownload",rscInstalltionStatus.getConfigdownload());
update.set("rscpkgdownload",rscInstalltionStatus.getRscpkgdownload());
update.set("configextraction",rscInstalltionStatus.getConfigextraction());
update.set("rscpkgextraction",rscInstalltionStatus.getRscpkgextraction());
update.set("rscstartup",rscInstalltionStatus.getRscstartup());
update.set("installedversion",rscInstalltionStatus.getInstalledversion());
mongoTemplate.upsert(query, update,RscInstalltionStatus.class);
rscInstalltionStatus = rscInstalltionStatusRepository.findByHostname(rscInstalltionStatus.getHostname());
return rscInstalltionStatusMapper.toDto(rscInstalltionStatus);
}
Update2 : with the below code i am able to get move the records to another collection
String query = "{$lookup:{ from: \"vmdetails\",let: {rschostname: \"$hostname\"},pipeline:[{$match:{$expr:{$ne :[\"$hostname\",\"$$rschostname\"]}}}],as: \"rscInstall\"}},{$unwind:\"$rscInstall\"},{$project:{\"_id\":0,\"rscInstall\":0}}";
AggregationOperation rscInstalltionStatusTypedAggregation = new CustomProjectAggregationOperation(query);
LookupOperation lookupOperation = LookupOperation.newLookup().from("vmdetails").localField("hostname").foreignField("hostname").as("rscInstall");
UnwindOperation unwindOperation = Aggregation.unwind("$rscInstall");
ProjectionOperation projectionOperation = Aggregation.project("_id","rscInstall").andExclude("_id","rscInstall");
OutOperation outOperation = Aggregation.out("RscInstallArchive");
Aggregation aggregation = Aggregation.newAggregation(rscInstalltionStatusTypedAggregation,unwindOperation,projectionOperation,outOperation);
List<BasicDBObject> results = mongoTemplate.aggregate(aggregation,"rsc_installtion_status",BasicDBObject.class).getMappedResults();
this issue which i have here is it returns multiple records

Answer 1

Found the solution , there may be other best solutions but for me this one worked
create a class customeAggregationGeneration (found in SO answers and extended to match my needs)
public class CustomProjectAggregationOperation implements AggregationOperation {
private String jsonOperation;
public CustomProjectAggregationOperation(String jsonOperation) {
this.jsonOperation = jsonOperation;
}
#Override
public Document toDocument(AggregationOperationContext aggregationOperationContext) {
return aggregationOperationContext.getMappedObject(Document.parse(jsonOperation));
}
}
String lookupquery = "{$lookup :{from:\"vmdetails\",localField:\"hostname\",foreignField:\"hostname\"as:\"rscinstall\"}}";
String matchquery = "{ $match: { \"rscinstall\": { $eq: [] } }}";
String projectquery = "{$project:{\"rscinstall\":0}}";
AggregationOperation lookupOpertaion = new CustomProjectAggregationOperation(lookupquery);
AggregationOperation matchOperation = new CustomProjectAggregationOperation(matchquery);
AggregationOperation projectOperation = new CustomProjectAggregationOperation(projectquery);
Aggregation aggregation = Aggregation.newAggregation(lookupOpertaion, matchOperation, projectOperation);
ArrayList<Document> results1 = (ArrayList<Document>) mongoTemplate.aggregate(aggregation, "rsc_installtion_status", Document.class).getRawResults().get("result");
// System.out.println(results1);
for (Document doc : results1) {
// System.out.print(doc.get("_id").toString());
mongoTemplate.insert(doc, "RscInstallArchive");
delete(doc.get("_id").toString());