Proper way to update mongo in patch action in web api

Question

I want to implement Patch action in web api, consider I have Customer collection in mongo like this:

public string Id{ get; set; }
public string Name{ get; set; }
public string Family{ get; set; }
public string Sex{ get; set; }
public string City{ get; set; }
public string CustomerId{ get; set; }

in my api i receive this object as input. client can edit one or many of these fields,if property is null it means the value should be remained previous value. what I want to do is in mongo query I wan to say if property is null dont update consider this:

var filter = Builders<Customer>.Filter.Eq(s => s.CustomerId, CustomerId);
var builder = Builders<Customer>.Update.Set(???)//set only not null values
mongo.UpdateOne(filter, builder);

*By the way any better solution for this is appreciated

Marcello · Accepted Answer · 2018-01-02T21:20:04.517

You might do something like this.

var filter = Builders<Customer>.Filter
    .Eq(s => s.CustomerId, customer.CustomerId); //perhaps requires an index on CustomerId field
var update = Builders<Customer>.Update
    .Set(p => p.CustomerId, customer.CustomerId);
if (!string.IsNullOrWhiteSpace(customer.City))
    update = update.Set(p => p.City, customer.City);
if (!string.IsNullOrWhiteSpace(customer.Name))
    update = update.Set(p => p.Name, customer.Name);
if (!string.IsNullOrWhiteSpace(customer.Family))
    update = update.Set(p => p.Family, customer.Family);
if (!string.IsNullOrWhiteSpace(customer.Sex))
    update = update.Set(p => p.Sex, customer.Sex);

customers.UpdateOne(filter, update);

A different approach might consider your customer entity as a whole (document oriented databases encourage this approach), thus always updating the entity altogether and avoiding fine-grained updates (that are more likely in case of R-DBMSs). In this case, you might write something like this.

var customerFromDb = customers
    .Find(p => p.CustomerId == customer.CustomerId)
    .Single();

if (!string.IsNullOrWhiteSpace(customer.City))
    customerFromDb.City = customer.City;
if (!string.IsNullOrWhiteSpace(customer.Name))
    customerFromDb.Name = customer.Name;
if (!string.IsNullOrWhiteSpace(customer.Family))
    customerFromDb.Family = customer.Family;
if (!string.IsNullOrWhiteSpace(customer.Sex))
    customerFromDb.Sex = customer.Sex;

customers.ReplaceOne(p => p.CustomerId == customer.CustomerId, customerFromDb);

This second approach has the following Pro and Cons.

Pro

the update happens in the domain-layer (possibly through well suited methods), thus allowing enforcement of all domain rules and preventing dirty data to go into the database; thus it is more object-oriented.

Cons

this approach requires two hits on the database (one for the read and one for the update);
in case your entity is large, network has to transport more data than strictly needed.

Considering that premature optimization is the root of all evil (or at least most of it) in programming (here), in general I would go for the second approach, falling back to the first one only in case of very strict performance requirements or low network bandwidth.

what is the reason behind this code:var update = Builders.Update .Set(p => p.CustomerId, customer.CustomerId); because we dont want to update this, is there any better way for solution one to avoid this update? — someone, Jan 03 '18 at 14:37
It grants that `update` variable holds a defined `UpdateDefinition` to be passed to `UpdateOne()` method, even if no updates are requested (i.e. in case all received properties are null). Alternatively, you might test the need for triggering the update. But this would request a full inspection of the data structure (quite unmaintainable) and would be possibly a premature optimization. — Marcello, Jan 03 '18 at 15:23

Proper way to update mongo in patch action in web api

1 Answers1

Pro

Cons