82 lines
3.1 KiB
Markdown
82 lines
3.1 KiB
Markdown
# RethinkDb.Driver.FSharp
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Idiomatic F# extensions for the C# RethinkDB driver
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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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## Using
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Install the [NuGet](https://www.nuget.org/packages/RethinkDb.Driver.FSharp/) package `RethinkDb.Driver.FSharp`. You will need to specify pre-release, as the package has an alpha designation at this time.
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## Goals
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The goal is to provide:
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- A composable pipeline for creating ReQL statements:
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```fsharp
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/// string -> (IConnection -> Task<Post>)
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let fetchPost (postId : string) =
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fromDb "Blog"
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|> table "Post"
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|> get postId
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|> runResult<Post>
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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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/// string -> (IConnection -> Task<Post>)
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let fetchPost (postId : string) =
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rethink<Post> {
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withTableInDb "Post" "Blog"
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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. Its names may change in the 0.8.x series; it is the most alpha part of the project at this point.
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The functions do have to change a bit, since they 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.["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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---
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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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[license]: https://github.com/bchavez/RethinkDb.Driver#open-source-and-commercial-licensing
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[nuget]: https://ci.appveyor.com/nuget/danieljsummers-rethinkdb-driver-fsharp |