An investigation into using F# and MongoDB for a line of business application.

1. Super Spike
Yep. It’s Super

2. Who am I?
Who I am?

3. Indoctrination
Reduction in fear
Super awesome MongoDB non-relational database tips
An introduction on how to use the MongoDB C# Driver
Super awesome F# functional programming tips
How to integrate F# into your apps today
Looks at some functional techniques
BONUS: (I hope) some inspiration

4. 1. Analyze transactional data
2. Create models for setting prices
3. Work with sales team to raise prices
4. Measure results

5. Narrow
Deep

6. • Mongo
– Unstructured data
– Flexible query language…using JavaScript!
– Feels…”light”
• F#
– Reasoning
• Less code
• No side effects
– Productivity
• fsi
• Focus on what, not where

7. • Data Access
– Mostly read-only
– Data processing heavy
– Non-standard formats from client to client
• Data Processing
– Calculate metrics on different slices of data
– Different formulas for various metrics

8. View (razor)
Controller (C#)
Model
Data Processing (F#)
(C#)
Data Access (F#)
MongoDB

9. • Current Situation
– Unknown schema
– Complex transformation scripts
– Complex loading scripts

12. static member Initialize() =
BsonClassMap.RegisterClassMap<Customer>(fun cm ->
cm.AutoMap()
cm.SetIdMember(cm.GetMemberMap("Number"))
) |> ignore
BsonClassMap.RegisterClassMap<Product>(fun cm ->
cm.AutoMap()
cm.SetIdMember(cm.GetMemberMap("SKU"))
) |> ignore

13. private static void ImportFromFile<T>(
string filename, Dictionary<string, int> fieldMappings)
where T: CoreObject {
var datafile = DataFile.FindOneById(filename);
var record = datafile.ReadLine();
while (record != null) {
var o = Activator.CreateInstance<T>();
o.Load(record, fieldMappings);
o.Save();
record = datafile.ReadLine();
}
}

14. {
"_id": "1234567",
"_t": "Customer",
"Attributes": {
"Parent": "Mike's Chocolates",
"Salesman": "Willy Wonka",
"Industry": "Candy"
},
"Name": "Choc a lot"
}
• Invoice
• Date
• Quantity
• Amount
• Customer
• Product

15. • Current Situation
– Hard to find
– Hard to test
– Calculations are often performed “on top of”
other calculations
– Technical team needs to explain how formulas
work

16. let GetCollection<'T>() =
(new MongoRepository())
.GetDatabase()
.GetCollection<'T> typeof<'T>.Name
let Invoices = GetCollection<Invoice>
let GetInvoices (fromDate:DateTime) (toDate:DateTime) includeFields =
let query = Query
.GTE("Date", BsonDateTime.Create(fromDate))
.LTE(BsonDateTime.Create(toDate))
let fields = Fields.Exclude("_id").Include(includeFields)
Invoices().Find(query).SetFields(fields) :> seq<Invoice>

17. static member GetRevenueByYear (fromDate:DateTime) (toDate:DateTime) =
GetInvoices fromDate toDate [|"Date"; "Amount"|]
|> Seq.groupBy (fun i -> i.Date.Year)
|> Seq.map (fun (year, invoices) -> (year, (sumRevenue invoices)))
|> Seq.sortBy (fun (year, _) -> year)
let sumRevenue (invoices:seq<Invoice>) =
invoices |> Seq.sumBy (fun i -> i.Amount)

19. let IndexByCustomer fromDate toDate operation attribute =
Index “Customer”
(fun i -> i.Customer.Attributes.[attribute])
fromDate toDate
operation
let IndexByProduct fromDate toDate operation attribute =
Index “Product”
(fun i -> i.Product.Attributes.[attribute])
fromDate toDate
operation
let Index type groupF fromDate toDate indexF
string -> (Invoice -> string) -> DateTime -> DateTime -> (seq<Invoice> -> float) ->
seq<string * float * float>

20. string -> (Invoice -> string) -> DateTime -> DateTime -> (seq<Invoice> -> float) ->
seq<string * float * float>
let IndexCustomers attribute =
Index "Customer" (fun (i:Invoice) -> i.Customer.Attributes.[attribute])
let IndexProducts attribute =
Index "Product" (fun (i:Invoice) -> i.Product.Attributes.[attribute])
string -> (DateTime -> DateTime -> (seq<Invoice> -> float) ->
seq<string * float * float>)
let IndexByCustomer fromDate toDate operation attribute =
IndexCustomers attribute fromDate toDate operation
let IndexByProduct fromDate toDate operation attribute =
IndexProducts attribute fromDate toDate operation

21. type Entity =
| Customer
| Product
let IndexEntity t attribute fromDate toDate indexOp =
let f =
match t with
| Customer -> IndexCustomers
| Product -> IndexProducts
f attribute fromDate toDate indexOp

22. OPERATIONAL DEVELOPMENT USER PERCEIVED
From days to minutes Reasoning about code “OK”
Closer to the data

24. mongodb.org
https://github.com/mongodb/mongo-csharp-driver
http://www.tryfsharp.org
FsUnit (via NuGet)
http://www.jqplot.com/

25. www: michaelfalanga.com
E-mail: me@michaelfalanga.com
Twitter: @mfalanga