I have inserted documents into MongoDB without an id. And I want to retrieve them by searching through their MongoDB ObjectId, that has been assigned in default.
Here is my attempt-
var query_id = Query.EQ("_id", "50ed4e7d5baffd13a44d0153");
var entity = dbCollection.FindOne(query_id);
return entity.ToString();
And I get following error-
A first chance exception of type 'System.NullReferenceException' occurred
What is the problem?
You need to create an instance of ObjectId and then query using that instance, otherwise your query compares ObjectIds to string and fails to find matching documents.
This should work:
var query_id = Query.EQ("_id", ObjectId.Parse("50ed4e7d5baffd13a44d0153"));
var entity = dbCollection.FindOne(query_id);
return entity.ToString();
In C# for latest official MongoDB.Driver write this-
var filter_id = Builders<MODEL_NAME>.Filter.Eq("id", ObjectId.Parse("50ed4e7d5baffd13a44d0153"));
var entity = dbCollection.Find(filter).FirstOrDefault();
return entity.ToString();
We can accomplish the same result without converting id from string to ObjectId. But then, we will have to add [BsonRepresentation(BsonType.ObjectId)] before id attribute in the model class.
The code can even be further simplified using lambda expression-
var entity = dbCollection.Find(document => document.id == "50ed4e7d5baffd13a44d0153").FirstOrDefault();
return entity.ToString();
If you're here in 2018 and want copy/paste code that still works or pure string syntax;
[Fact]
public async Task QueryUsingObjectId()
{
var filter = Builders<CosmosParkingFactory>.Filter.Eq("_id", new ObjectId("5b57516fd16cb04bfc35fcc6"));
var entity = stocksCollection.Find(filter);
var stock = await entity.SingleOrDefaultAsync();
Assert.NotNull(stock);
var idString = "5b57516fd16cb04bfc35fcc6";
var stringFilter = "{ _id: ObjectId('" + idString + "') }";
var entityStringFiltered = stocksCollection.Find(stringFilter);
var stockStringFiltered = await entityStringFiltered.SingleOrDefaultAsync();
Assert.NotNull(stockStringFiltered);
}
The selected answer is correct. For anyone confused by the Query.EQ, here is another way to write a basic update (updates the entire mongodb document):
string mongoDocumentID = "123455666767778";
var query = new QueryDocument("_id", ObjectId.Parse(mongoDocumentID));
var update = new UpdateDocument { { "$set", documentToSave } };
mongoCollection.Update(query, update, UpdateFlags.Multi);
The ObjectId object is needed when you want to actually search by object ID, otherwise it is comparing string to objectid type, and it won't match. Mongo is very type-strict in this way, regardless if the field name is correct.
You can also do it this way, its
public static ObjectId GetInternalId(string id)
{
if (!ObjectId.TryParse(id, out ObjectId internalId))
internalId = ObjectId.Empty;
return internalId;
}
then in your method you can do something like this
ObjectId internalId = GetMongoId.GetInternalId(id);
return await YourContext.YourTable.Find(c => c.InternalId == internalId).FirstOrDefaultAsync();
Note: id param in GetInternalId its a parameter on that method. In case you need as this:
public async Task<YourTable> Find(string id)
{
ObjectId internalId = GetMongoId.GetInternalId(id);
return await YourContext.YourTable.Find(c => c.InternalId == internalId).FirstOrDefaultAsync();
}
Hope it helps also.
Related
I am trying to filter my data based on the two factors. The first factor is the docID(object Id) and the second factor is DocType which is stored as metadata. The sample code I am pasting.I am also attaching the sample DB how it looks like.
public async Task<ActionResult> DeleteDocument([FromRoute] int docType, [FromRoute] string docId)
{
try
{
var filter = Builders<GridFSFileInfo>.Filter.And(
Builders<GridFSFileInfo>.Filter.Eq(x => x.Metadata.GetValue("DocType"), docType),
Builders<GridFSFileInfo>.Filter.Eq(x => x.Id.ToString(), docId));
using (var cursor = await Bucket.FindAsync(filter))
{
var fileInfos = (await cursor.ToListAsync());
foreach (GridFSFileInfo fileInfo in fileInfos)
{
foreach (BsonElement bsonE in fileInfo.Metadata.ToList())
{
Console.WriteLine(fileInfo.Filename);
}
}
}
}
But I am not getting the correct result it giving me errors. Can anyone please point out what I am doing wrong or how to write filters based on metadata information.
Looks like they're a few problems with the above code. The MongoDB Driver is struggling with converting these expressions into a MongoDB Query.
.Eq(x => x.Metadata.GetValue("DocType"), docType)
.Eq(x => x.Id.ToString(), docId)
This is because you need to use the indexer to accessing fields of the metadata, also you'll need to change docId into the correct type before comparing it against the Id field.
Try the following filter out.
var docType = 1;
var docId = ObjectId.Parse("5f3ce002796ba13443aa4bc5");
var filter =
Builders<GridFSFileInfo<ObjectId>>.Filter.Eq(x => x.Metadata["DocType"], docType)
& Builders<GridFSFileInfo<ObjectId>>.Filter.Eq(x => x.Id, docId);
I currently have a project that I'm working on, which has a database connected to it. In said database I need to query some tables that don't have a relationship. I need to get a specific set of data in order to display it on my user interface. However I need to be able to reference the returned data put it into a list and convert it into json. I have a stored procedure that needs to just be executed against the context because it's retrieving data from many different tables.
I've tried using ExecuteSqlCommand but that doesn't work, because it returns -1 and can't put it into a list.
I've tried using linq to select the columns I want however it's really messy and I cannot retrieve the data as easily.
I've tried using FromSql, however that needs a model to execute against the context which is exactly what I don't want.
public string GetUserSessions(Guid memberId)
{
string sql = $"EXECUTE dbo.GetUserTrackByMemberID #p0";
var session = _context.Database.ExecuteSqlCommand(sql, memberId);
var json = JsonConvert.SerializeObject(session);
return json;
}
This is the ExecuteSqlCommand example, this returns -1 and cannot be put into a list as there will be more than one session.
public string GetUserSessions(Guid memberId)
{
var session = _context.MemberSession.Where(ms => ms.MemberId == memberId).Select(s => new Session() { SessionId =
s.SessionId, EventId = s.Session.EventId, CarCategory = s.Session.CarCategory, AirTemp = s.Session.AirTemp,
TrackTemp = s.Session.TrackTemp, Weather = s.Session.Weather, NumberOfLaps = s.Session.NumberOfLaps, SessionLength = s.Session.SessionLength,
Event = new Event() { EventId = s.Session.Event.EventId, TrackId = s.Session.Event.TrackId, Name = s.Session.Event.Name, NumberOfSessions =
s.Session.Event.NumberOfSessions, DateStart = s.Session.Event.DateStart, DateFinish = s.Session.Event.DateFinish, TyreSet = s.Session.Event.TyreSet,
Track = new Track() { TrackId = s.Session.Event.Track.TrackId, Name = s.Session.Event.Track.Name, Location = s.Session.Event.Track.Location, TrackLength
= s.Session.Event.Track.TrackLength, NumberOfCorners = s.Session.Event.Track.NumberOfCorners} } });
var json = JsonConvert.SerializeObject(session);
return json;
}
This is using Linq, however it's really messy and I feel there's probably a better way to do this, and then when retrieving the data from json it's a lot bigger pain.
public string GetUserSessions(Guid memberId)
{
var session = _context.MemberSession.FromSql($"EXECUTE dbo.GetUserSessionByMemberID {memberId}").ToList();
var json = JsonConvert.SerializeObject(session);
return json;
}
This is the ideal way I would like to do it, however since I'm using the MemberSession model it will only retrieve that data from the stored procedure which is in the MemberSession table, however I want data that is in other tables as well....
public string GetUserSessions(Guid memberId)
{
var session = _context.MemberSession.Where(ms => ms.MemberId == memberId).Include("Session").Include("Event").ToList();
var json = JsonConvert.SerializeObject(session);
return json;
}
I tried this way but because the Event table has no reference / relationship to MemberSession it returns an error.
As I've previously stated in the RawSql example I'm only getting the table data that is in the MemberSession table, no other tables.
There are no error messages.
using (var context = new DBEntities())
{
string query = $"Exec [dbo].[YOUR_SP]";
List<ResponseList> obj = context.Database.SqlQuery<ResponseList>(query).ToList();
string JSONString = JsonConvert.SerializeObject(obj);
}
When data from a device goes into the elastic there are duplicates. I like to avoid this duplicates. I'm using a object of IElasticClient, .NET and NEST to put data.
I searched for a method like ElasticClient.SetDocumentId(), but cant find.
_doc doc = (_doc)obj;
HashObject hashObject = new HashObject { DataRecordId = doc.DataRecordId, TimeStamp = doc.Timestamp };
// hashId should be the document ID.
int hashId = hashObject.GetHashCode();
ElasticClient.IndexDocumentAsync(doc);
I would like to update the data set inside the Elastic instead of adding one more same object right now.
Assuming the following set up
var pool = new SingleNodeConnectionPool(new Uri("http://localhost:9200"));
var settings = new ConnectionSettings(pool)
.DefaultIndex("example")
.DefaultTypeName("_doc");
var client = new ElasticClient(settings);
public class HashObject
{
public int DataRecordId { get; set; }
public DateTime TimeStamp { get; set; }
}
If you want to set the Id for a document explicitly on the request, you can do so with
Fluent syntax
var indexResponse = client.Index(new HashObject(), i => i.Id("your_id"));
Object initializer syntax
var indexRequest = new IndexRequest<HashObject>(new HashObject(), id: "your_id");
var indexResponse = client.Index(indexRequest);
both result in a request
PUT http://localhost:9200/example/_doc/your_id
{
"dataRecordId": 0,
"timeStamp": "0001-01-01T00:00:00"
}
As Rob pointed out in the question comments, NEST has a convention whereby it can infer the Id from the document itself, by looking for a property on the CLR POCO named Id. If it finds one, it will use that as the Id for the document. This does mean that an Id value ends up being stored in _source (and indexed, but you can disable this in the mappings), but it is useful because the Id value is automatically associated with the document and used when needed.
If HashObject is updated to have an Id value, now we can just do
Fluent syntax
var indexResponse = client.IndexDocument(new HashObject { Id = 1 });
Object initializer syntax
var indexRequest = new IndexRequest<HashObject>(new HashObject { Id = 1});
var indexResponse = client.Index(indexRequest);
which will send the request
PUT http://localhost:9200/example/_doc/1
{
"id": 1,
"dataRecordId": 0,
"timeStamp": "0001-01-01T00:00:00"
}
If your documents do not have an id field in the _source, you'll need to handle the _id values from the hits metadata from each hit yourself. For example
var searchResponse = client.Search<HashObject>(s => s
.MatchAll()
);
foreach (var hit in searchResponse.Hits)
{
var id = hit.Id;
var document = hit.Source;
// do something with them
}
Thank you very much Russ for this detailed and easy to understand description! :-)
The HashObject should be just a helper to get a unique ID from my real _doc object. Now I add a Id property to my _doc class and the rest I will show with my code below. I get now duplicates any more into the Elastic.
public void Create(object obj)
{
_doc doc = (_doc)obj;
string idAsString = doc.DataRecordId.ToString() + doc.Timestamp.ToString();
int hashId = idAsString.GetHashCode();
doc.Id = hashId;
ElasticClient.IndexDocumentAsync(doc);
}
Am completely new to Mongodb and C# driver.
Development is being done using Monodevelop on Ubuntu 14.04 and Mongodb's version is 3.2.10 :
Currently my code has a POCO as below:
public class User
{
public String Name { get; set;}
public DateTime LastModifiedAt { get; set;}
public DateTime LastSyncedAt { get; set;}
public User ()
{
}
}
Have been able to create a collection and also to add users.
How do I find users, whose LastModifiedAt timestamp is greater than LastSyncedAt timestamp ? Did some searching, but haven't been able to find the answer.
Any suggestions would be of immense help
Thanks
Actually, it is not very simple. This should be possible with querysuch as :
var users = collection.Find(user => user.LastModifiedAt > user.LastSyncedAt).ToList();
But unfortunetly MongoDriver could not translate this expression.
You could either query all Users and filter on the client side:
var users = collection.Find(Builders<User>.Filter.Empty)
.ToEnumerable()
.Where(user => user.LastModifiedAt > user.LastSyncedAt)
.ToList();
Or send json query, because MongoDb itself is able to do it:
var jsonFliter = "{\"$where\" : \"this.LastModifiedAt>this.LastSyncedAt\"}";
var users = collection.Find(new JsonFilterDefinition<User>(jsonFliter))
.ToList();
And, yes, you need an Id - Property for your model class, i haven't mentioned it first, because i thought you do have one, just not posted in the question.
There is another way to do it. First lets declare collection:
var collection = Database.GetCollection<BsonDocument>("CollectionName");
Now lets add our project:
var pro = new BsonDocument {
{"gt1", new BsonDocument {
{ "$gt", new BsonArray(){ "$LastModifiedAt", "$LastSyncedAt" }
}
} },
{"Name", true },
{"LastModifiedAt", true },
{"LastSyncedAt", true }
};
Now lets add our filter:
var filter = Builders<BsonDocument>.Filter.Eq("gt1", true);
We'll aggregate our query:
var aggregate = collection.Aggregate(new AggregateOptions { AllowDiskUse = true })
.Project(pro)
.Match(filter)
Now our query is ready. We can check our query as follow:
var query=aggregate.ToString();
Lets run our query as follow:
var query=aggregate.ToList();
This with return the required data in list of bson documents.
This solution will work mongo c# driver 3.6 or above. Please comment in case of any confusion. Hopefully i'll able to explain this.
I am building some abstraction functions for my application to call, which will hit elasticsearch through Nest. One of such functions is a Delete(string id) call, which is easy to accomplish. I have done this as follows:
public void Delete(string id)
{
esClient.Delete(id);
}
Now let's say I want to do the same thing, but operate on several documents simultaneously. My original hunch was to do something like this:
public void Delete(IEnumerable<string> ids)
{
esClient.DeleteMany(ids); // won't compile
}
As my comment states, doing this won't compile. What is the proper way of batch deleting documents by ID in Nest?
To use esClient.DeleteMany(..) you have to pass collection of objects to delete.
var objectsToDelete = new List<YourType> {.. };
var bulkResponse = client.DeleteMany<YourType>(objectsToDelete);
You can get around this by using following code:
var ids = new List<string> {"1", "2", "3"};
var bulkResponse = client.DeleteMany<YourType>(ids.Select(x => new YourType { Id = x }));
Third option, use bulk delete:
var bulkResponse = client.Bulk(new BulkRequest
{
Operations = ids.Select(x => new BulkDeleteOperation<YourType>(x)).Cast<IBulkOperation>().ToList()
});
I was working on a .NET client for ElasticSearch 5.x, and I was fortunate to have the following code running (as well as succeeding all unit tests) for bulk deletion using ID's:
//IList<string> ids = ...
var descriptor = new BulkDescriptor();
foreach (var id in ids.Where(x => !string.IsNullOrWhiteSpace(x)))
descriptor.Delete<T>(x => x
.Id(id))
.Refresh(Refresh.WaitFor);
var response = await _client.BulkAsync(descriptor);