F# Support for LiteDB
This package relies on LiteDB 4.14 >= version > 5.0 Support for v5 is work in progress and might require a full rewrite.
LiteDB.FSharp provides serialization utilities making it possible for LiteDB to understand F# types such as records, unions, maps etc. with support for type-safe query expression through F# quotations
LiteDB.FSharp comes with a custom BsonMapper called FSharpBsonMapper that you would pass to a LiteDatabase instance during initialization:
open LiteDB
open LiteDB.FSharp
open LiteDB.FSharp.Extensions
let mapper = FSharpBsonMapper()
use db = new LiteDatabase("simple.db", mapper)
LiteDB.FSharp is made mainly to work with records as representations of the persisted documents. The library requires that records have a primary key called Id or id. This field is then mapped to _id when converted to a bson document for indexing.
type Genre = Rock | Pop | Metal
type Album = {
Id: int
Name: string
DateReleased: DateTime
Genre: Genre
}
Get a typed collection from the database:
let albums = db.GetCollection<Album>("albums")
let metallica =
{ Id = 1;
Name = "Metallica";
Genre = Metal;
DateReleased = DateTime(1991, 8, 12) }
albums.Insert(metallica)
// result : Album let result = albums.findOne <@ fun album -> album.Id = 1 @> // OR let id = BsonValue(1) // result : Album let result = albums.FindById(id)Query many documents depending on the value of a field
// metallicaAlbums : Seq<Album>
let metallicaAlbums = albums.findMany <@ fun album -> album.Name = "Metallica" @>
// OR
let name = BsonValue("Metallica")
let query = Query.EQ("Name", name)
// metallicaAlbums : Seq<Album>
let metallicaAlbums = albums.Find(query) Query documents by value of discriminated union
// find all albums where Genre = Rock
// rockAlbums : Seq<Album>
let rockAlbums = albums.findMany <@ fun album -> album.Genre = Rock @>
// OR
let genre = BsonValue("Rock")
let query = Query.EQ("Genre", genre)
// rockAlbums : Seq<Album>
let rockAlbums = albums.Find(query) Query documents between or time intervals
// find all albums released last year
let now = DateTime.Now
let dateFrom = DateTime(now.Year - 1, 01, 01) |> BsonValue
let dateTo = DateTime(now.Year, 01, 01) |> BsonValue
let query = Query.Between("DateReleased", dateFrom, dateTo)
// albumsLastYear : Seq<Album>
let albumsLastYear = albums.Find(query) Customized Full Search using quoted expressions
// Filtering albums released a year divisble by 5
// filtered : Seq<Album>
let filtered =
albums.fullSearch
<@ fun album -> album.DateReleased @>
(fun dateReleased -> dateReleased.Year % 5 = 0) Customized Full Search using Query.Where
The function Query.Where expects a field name and a filter function of type BsonValue -> bool. You can deserialize the BsonValue using Bson.deserializeField<'t> where 't is the type of the serialized value.
// Filtering albums released a year divisble by 5
let searchQuery =
Query.Where("DateReleased", fun bsonValue ->
// dateReleased : DateTime
let dateReleased = Bson.deserializeField<DateTime> bsonValue
let year = dateReleased.Year
year % 5 = 0
)
let searchResult = albums.Find(searchQuery) Query.Where: Filtering documents by matching with values of a nested DU
type Shape =
| Circle of float
| Rect of float * float
| Composite of Shape list
type RecordWithShape = { Id: int; Shape: Shape }
let records = db.GetCollection<RecordWithShape>("shapes")
let shape =
Composite [
Circle 2.0;
Composite [ Circle 4.0; Rect(2.0, 5.0) ]
]
let record = { Id = 1; Shape = shape }
records.Insert(record) |> ignore
let searchQuery =
Query.Where("Shape", fun bsonValue ->
let shapeValue = Bson.deserializeField<Shape> bsonValue
match shapeValue with
| Composite [ Circle 2.0; other ] -> true
| otherwise -> false
)
records.Find(searchQuery)
|> Seq.length
|> function
| 1 -> pass() // passed!
| n -> fail()
Add CLIMutableAttribute to record type and set Id 0
[<CLIMutable>]
type Album = {
Id: int
Name: string
DateReleased: DateTime
Genre: Genre
}
let metallica =
{ Id = 0;
Name = "Metallica";
Genre = Metal;
DateReleased = DateTime(1991, 8, 12) }
just as https://github.com/mbdavid/LiteDB/wiki/DbRef
open LiteDB.FSharp.Linq
[<CLIMutable>]
type Company=
{ Id : int
Name : string}
[<CLIMutable>]
type Order=
{ Id :int
Company :Company }
let mapper = FSharpBsonMapper()
mapper.DbRef<Order,_>(fun c -> c.Company)
Item1 and Item2 are inherited from IItem
we must register the type relations first globally
FSharpBsonMapper.RegisterInheritedConverterType<IItem,Item1>() FSharpBsonMapper.RegisterInheritedConverterType<IItem,Item2>()
By conversion, The inherited type must has mutable field for serializable and deserializable
Note: Because json converter find inherited type by comparing the fields names from inherited type and database
let findType (jsonFields: seq<string>) =
inheritedTypes |> Seq.maxBy (fun tp ->
let fields = tp.GetFields() |> Seq.map (fun fd -> fd.Name)
let fieldsLength = Seq.length fields
(jsonFields |> Seq.filter(fun jsonField ->
Seq.contains jsonField fields
)
|> Seq.length),-fieldsLength
)
This means that we should not implement the some interface with different fields For example,we should not do below implementations
type Item1 =
val mutable Id : int
val mutable Art : string
val mutable Name : string
val mutable Number : int
interface IItem with
member this.Art = this.Art
member this.Id = this.Id
member this.Name = this.Name
member this.Number = this.Number
/// unexpected codes
type Item2 =
val mutable Id2 : int
val mutable Art2 : string
val mutable Name2 : string
val mutable Number2 : int
interface IItem with
member this.Art = this.Art2
member this.Id = this.Id2
member this.Name = this.Name2
member this.Number = this.Number2
/// expected codes
type Item2 =
val mutable Id : int
val mutable Art : string
val mutable Name : string
val mutable Number : int
interface IItem with
member this.Art = this.Art
member this.Id = this.Id
member this.Name = this.Name
member this.Number = this.Number
Full sample codes:
/// classlibray.fs
[<CLIMutable>]
type EOrder=
{ Id: int
Items : IItem list
OrderNumRange: string }
/// consumer.fs
type Item1 =
/// val mutable will make field serializable and deserializable
val mutable Id : int
val mutable Art : string
val mutable Name : string
val mutable Number : int
interface IItem with
member this.Art = this.Art
member this.Id = this.Id
member this.Name = this.Name
member this.Number = this.Number
val mutable Barcode : string
interface IBarcode with
member this.Barcode = this.Barcode
/// type constructor
new (id, art, name, number, barcode) =
{ Id = id; Art = art; Name = name; Number = number; Barcode = barcode }
type Item2 =
val mutable Id : int
val mutable Art : string
val mutable Name : string
val mutable Number : int
interface IItem with
member this.Art = this.Art
member this.Id = this.Id
member this.Name = this.Name
member this.Number = this.Number
val mutable Size : int
interface ISize with
member this.Size = this.Size
val mutable Color : string
interface IColor with
member this.Color = this.Color
new (id, art, name, number, size, color) =
{ Id = id; Art = art; Name = name; Number = number; Size = size; Color = color }
FSharpBsonMapper.RegisterInheritedConverterType<IItem,Item1>()
FSharpBsonMapper.RegisterInheritedConverterType<IItem,Item2>()
let item1 =
Item1 (
id = 0,
art = "art",
name = "name",
number = 1000,
barcode = "7254301"
)
let item2 =
Item2 (
id = 0,
art = "art",
name = "name",
number = 1000,
color = "red" ,
size = 39
)
let eorder = { Id = 1; Items = [item1;item2]; OrderNumRange = "" }
let queryedEOrder =
db
|> LiteRepository.insertItem eorder
|> LiteRepository.query<EOrder>
|> LiteQueryable.first
match queryedEOrder.Items with
| [item1;item2] ->
match item1,item2 with
| :? IBarcode,:? IColor ->
pass()
| _ -> fail()
| _ -> fail()
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