Meet Donald (Chamberlin).
If you're a programmer and have used a database, he's impacted your life in a big way.
This library is named after him.
Honorable mention goes to @dsyme another important Donald and F#'s BDFL.
Donald is a generic library that aims to make working with ADO.NET safer and more succinct. It is an entirely generic abstraction, and will work with all ADO.NET implementations.
- Support all ADO implementations
- Provide a succinct, type-safe API for interacting with databases
- Enable asynchronuos workflows
- Make object mapping easier
- Improve data access performance
- Provide additional context during exceptions
Install the Donald NuGet package:
PM> Install-Package Donald
Or using the dotnet CLI
dotnet add package Donaldopen Donald
type Author =
{ FullName : string }
let authors (conn : IDbConnection) : Author list =
conn
|> Db.newCommand "
SELECT full_name
FROM author
WHERE author_id = @author_id"
|> Db.setParams [
"author_id", SqlType.Int32 1 ]
|> Db.query (fun rd ->
{ FullName = rd.ReadString "full_name" })For this example, assume we have an IDbConnection named conn:
Reminder: Donald will work with any ADO implementation (SQL Server, SQLite, MySQL, Postgresql etc.).
Consider the following model:
type Author =
{ AuthorId : int
FullName : string }
module Author -
let ofDataReader (rd : IDataReader) : Author =
{ AuthorId = rd.ReadInt32 "author_id"
FullName = rd.ReadString "full_name" }Important: Donald is set to use
CommandBehavior.SequentialAccessby default. See performance for more information.
conn
|> Db.newCommand "SELECT author_id, full_name FROM author"
|> Db.query Author.ofDataReader // Author list
// Async
conn
|> Db.newCommand "SELECT author_id, full_name FROM author"
|> Db.Async.query Author.ofDataReader // Task<Author list>conn
|> Db.newCommand "SELECT author_id, full_name FROM author"
|> Db.setParams [ "author_id", SqlType.Int32 1 ]
|> Db.querySingle Author.ofDataReader // Author option
// Async
conn
|> Db.newCommand "SELECT author_id, full_name FROM author"
|> Db.setParams [ "author_id", SqlType.Int32 1 ]
|> Db.Async.querySingle Author.ofDataReader // Task<Author option>conn
|> Db.newCommand "INSERT INTO author (full_name) VALUES (@full_name)"
|> Db.setParams [ "full_name", SqlType.String "John Doe" ]
|> Db.exec // unit
// Async
conn
|> Db.newCommand "INSERT INTO author (full_name) VALUES (@full_name)"
|> Db.setParams [ "full_name", SqlType.String "John Doe" ]
|> Db.Async.exec // Task<unit>conn
|> Db.newCommand "INSERT INTO author (full_name) VALUES (@full_name)"
|> Db.execMany [
"full_name", SqlType.String "John Doe"
"full_name", SqlType.String "Jane Doe" ] // unit
// Async
conn
|> Db.newCommand "INSERT INTO author (full_name) VALUES (@full_name)"
|> Db.Async.execMany [
"full_name", SqlType.String "John Doe"
"full_name", SqlType.String "Jane Doe" ] //Task<unit>This can be accomplished in two ways:
- Using
Db.batchorDb.Async.batchwhich processes the action in an all-or-none fashion.
conn
|> Db.batch (fun tran ->
for fullName in [ "John Doe"; "Jane Doe" ] do
tran
|> Db.newCommandForTransaction "INSERT INTO author (full_name) VALUES (@full_name)"
|> Db.setParams ["full_name", SqlType.String fullName ]
|> Db.exec)- Using the extension methods:
TryBeginTransaction(),TryCommit()andTryRollback().
// Safely begin transaction or throw CouldNotBeginTransactionError on failure
use tran = conn.TryBeginTransaction()
for fullName in [ "John Doe"; "Jane Doe" ] do
tran
|> Db.newCommandForTransaction "INSERT INTO author (full_name) VALUES (@full_name)"
|> Db.setParams ["full_name", SqlType.String fullName ]
|> Db.exec
// Attempt to commit, will rollback automatically on failure, or throw DbTransactionException
tran.TryCommit ()
// Will rollback or throw DbTransactionException
// tran.TryRollback ()Command parameters are represented by SqlType which contains a case for all relevant types.
type SqlType =
| Null
| String of string
| AnsiString of string
| Boolean of bool
| Byte of byte
| Char of char
| AnsiChar of char
| Decimal of decimal
| Double of double
| Float of float
| Guid of Guid
| Int16 of int16
| Int32 of int32
| Int of int32
| Int64 of int64
| DateTime of DateTime
| Bytes of byte[]
let p1 : SqlType = SqlType.Null
let p2 : SqlType = SqlType.Int32 1Helpers also exist which implicitly call the respective F# conversion function. Which can be especially useful when you are working with value types in your program.
let p1 : SqlType = sqlInt32 "1" // equivalent to SqlType.Int32 (int "1")To make obtaining values from reader more straight-forward, 2 sets of extension methods are available for:
- Get value, automatically defaulted
- Get value as
option<'a>
Assuming we have an active IDataReader called rd and are currently reading a row, the following extension methods are available to simplify reading values:
rd.ReadString "some_field" // string -> string
rd.ReadBoolean "some_field" // string -> bool
rd.ReadByte "some_field" // string -> byte
rd.ReadChar "some_field" // string -> char
rd.ReadDateTime "some_field" // string -> DateTime
rd.ReadDecimal "some_field" // string -> Decimal
rd.ReadDouble "some_field" // string -> Double
rd.ReadFloat "some_field" // string -> float32
rd.ReadGuid "some_field" // string -> Guid
rd.ReadInt16 "some_field" // string -> int16
rd.ReadInt32 "some_field" // string -> int32
rd.ReadInt64 "some_field" // string -> int64
rd.ReadBytes "some_field" // string -> byte[]
rd.ReadStringOption "some_field" // string -> string option
rd.ReadBooleanOption "some_field" // string -> bool option
rd.ReadByteOption "some_field" // string -> byte option
rd.ReadCharOption "some_field" // string -> char option
rd.ReadDateTimeOption "some_field" // string -> DateTime option
rd.ReadDecimalOption "some_field" // string -> Decimal option
rd.ReadDoubleOption "some_field" // string -> Double option
rd.ReadFloatOption "some_field" // string -> float32 option
rd.ReadGuidOption "some_field" // string -> Guid option
rd.ReadInt16Option "some_field" // string -> int16 option
rd.ReadInt32Option "some_field" // string -> int32 option
rd.ReadInt64Option "some_field" // string -> int64 option
rd.ReadBytesOption "some_field" // string -> byte[] optionIf you need an explicit
Nullable<'a>you can useOption.asNullable.
Several custom exceptions exist which interleave the exceptions thrown by ADO.NET with contextually relevant metadata.
/// Details of failure to connection to a database/server.
type DbConnectionException =
inherit Exception
val ConnectionString : string option
/// Details of failure to execute database command or transaction.
type DbExecutionException =
inherit Exception
val Statement : string option
val Step : DbTransactionStep option
/// Details of failure to access and/or cast an IDataRecord field.
type DbReaderException =
inherit Exception
val FieldName : string option
/// Details of failure to commit or rollback an IDbTransaction
type DbTransactionException =
inherit Exception
val Step : DbTransactionStepBy default, the IDataReader is consumed using CommandBehavior.SequentialAccess. This allows the rows and columns to be read in chunks (i.e., streamed), but forward-only. As opposed to being completely read into memory all at once, and readable in any direction. The benefits of this are particular felt when reading large CLOB (string) and BLOB (binary) data. But is also a measureable performance gain for standard query results as well.
The only nuance to sequential access is that columns must be read in the same order found in the SELECT clause. Aside from that, there is no noticeable difference from the perspective of a library consumer.
Configuring CommandBehavior can be done two ways:
let sql = "SELECT author_id, full_name FROM author"
conn
|> Db.newCommand sql
|> Db.setCommandBehavior CommandBehavior.Default
|> Db.query Author.ofDataReaderThere's an issue for that.
Built with ♥ by Pim Brouwers in Toronto, ON. Licensed under Apache License 2.0.