96 lines
4.0 KiB
Markdown
96 lines
4.0 KiB
Markdown
# RethinkDb.Driver.FSharp
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Idiomatic F# extensions for the C# RethinkDB driver
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[![Nuget (with prereleases)][pkg-img]][pkg-url]
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## Using
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Install the [NuGet][pkg-url] package `RethinkDb.Driver.FSharp`. You will need to specify pre-release, as the package currently has a beta designation.
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## What It Provides
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The full documentation is on [the project site][project]; TL;DR below.
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### A composable pipeline for creating ReQL statements
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```fsharp
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open RethinkDb.Driver.FSharp.Functions
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/// string -> (IConnection -> Task<Post option>)
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let fetchPost (postId : string) =
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db "Blog"
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|> table "Post"
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|> get postId
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|> runResult<Post>
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|> asOption
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|> withRetryDefault
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```
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### An F# domain-specific language (DSL) using a `rethink` computation expression (CE)
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```fsharp
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open RethinkDb.Driver.FSharp
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/// string -> (IConnection -> Task<Post>)
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let fetchPost (postId : string) =
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rethink<Post> {
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withTable "Blog.Post"
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get postId
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result
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withRetryDefault
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}
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```
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### A standard way to translate JSON into a strongly-typed configuration
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```fsharp
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/// type: DataConfig
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let config = DataConfig.fromJsonFile "data-config.json"
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// OR
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let config = DataConfig.fromConfiguration (config.GetSection "RethinkDB")
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/// type: IConnection
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let conn = config.Connect ()
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/// type: Post (utilizing either example above)
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// (within a task CE)
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let! post = fetchPost "the-post-id" conn
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```
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### Robust queries
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The RethinkDB connection is generally stored as a singleton. Over time, this connection can lose its connection to the server. Both the CE and functions have `withRetryDefault`, which will retry a failed command up to 3 times (4 counting the initial try), waiting 200ms, 500ms, and 1 second between the respective attempts. There are other options as well; `withRetryOnce` will retry one time immediately. `withRetry` takes a list of `float`s, which will be interpreted as seconds to delay between each retry; it will retry until it has exhausted the delays.
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The examples above both use the default retry logic.
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### Only rename functions/methods where required
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Within the CE, there are a few differing names, mostly notably at the start (selecting databases and tables); this is to allow for a more natural language flow. Also, while CEs now support overloading (thank you F# 6 developers!), they do not detect if the first value in the tupled arguments is different. This is most noticeable once `result*` or `write*` commands have been issued; these support `Task<'T>`, `Async<'T>`, and synchronous `'T` operations, but the follow-on commands will be different (e.x. `withRetryDefault` (tasks) vs. `withAsyncRetryDefault` vs. `withSyncRetryDefault`). There are also versions of these that support optional arguments (for all) and cancellation tokens (for task/async).
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The functions show this pattern throughout, as functions in a module do not support overloading; an example for `filter` is below.
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```fsharp
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// Function names cannot be polymorphic the way object-oriented methods can, so filter's three overloads become
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filter (r.HashMap ("age", 30))
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// and
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filterFunc (fun row -> row.G("age").Eq 30)
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// and
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filterJS "function (row) { return 30 == row['age'] }"
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```
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Functions that support optional arguments end with `WithOptArgs`; those that support cancellation tokens end with `WithCancel`; and, those that support both end with `WithOptArgsAndCancel`.
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## Licensing
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While no specific additional license restrictions exist for this project, there are modifications to the Apache v2
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license on this project's dependencies. Please see [the heading on the C# driver page][license] for details.
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---
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If you are using the project, feel free to file issues about your pain points; there is no substitute for real-world feedback!
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[pkg-img]: https://img.shields.io/nuget/vpre/RethinkDb.Driver.FSharp
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[pkg-url]: https://www.nuget.org/packages/RethinkDb.Driver.FSharp/
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[project]: https://bitbadger.solutions/open-source/rethinkdb-driver-fsharp/
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[license]: https://github.com/bchavez/RethinkDb.Driver#open-source-and-commercial-licensing
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