Learn Introspection Queries in GraphQL

What is Introspection in GraphQL

GraphQL stands out with its strong type system. Because of the strong typed system, GraphQL is able to provide an introspection system to query the schema. The introspection system in GraphQL provides a way for clients to discover the resources that are available in a GraphQL schema. The introspection system is a feather in the hat for GraphQL. It has plenty of uses and we will see some of them below.

Why is Introspection Useful?

Provides clients a deep view of the schema

Through introspection queries, the client can get a complete view of the resources in the GraphQL schema. This can save the client tons of time going back and forth with documentation. Instead they can introspect the schema and understand the resources available to them in depth.

Build Awesome Tools

The introspection system allows the community to build awesome tools for GraphQL. Some of the tools that we use today that owe their existence to the introspection system are GraphiQL, GraphQL Playground, to name a few. These tools help clients to explore the GraphQL schema, in an easy and user-interactive way.

Self Documentation

These GraphQL tools like GraphQL Playground use the introspection system, to provide features like self documentation of the API, auto completion and code generation.

Introspection Queries

Let’s dive into some introspection queries and learn how to write them.

To demonstrate and learn GraphQL introspection queries, I am going to use the GitHub API that is available to the public. You can follow along by opening https://developer.github.com/v4/explorer/. Make sure you are signed in to your GitHub account to run the introspection queries.

On the GitHub GraphQL explorer, we can start typing our queries on the left side and hit play to see the JSON response on the right side. We can also browse through the documentation of the API on the right side.

Query schema’s type

All the fields in the introspection system are prefixed with two underscores. Let’s query the __schema field and learn about the types supported in the schema.

query getSchmemaTypes {
  __schema {
    types {
      name
    }
  }
}

The JSON response to this query is quite lengthy from the GitHub schema, below is the snapshot of the response.

{
  "data": {
    "__schema": {
      "types": [
        {
          "name": "AcceptEnterpriseAdministratorInvitationInput"
        },
        {
          "name": "AcceptEnterpriseAdministratorInvitationPayload"
        },
        {
          "name": "AcceptTopicSuggestionInput"
        },
        {
          "name": "AcceptTopicSuggestionPayload"
        }
        ......
       ]
    }
  }
}

Query supported queries and mutations

Using introspection we can also retrieve the supported queries and mutations from a schema. You can also use the isDeprecated field to learn if specific queries/mutations are deprecated. This will be useful information for the client before consuming the API. Within the ___schema _field, query for queryType and mutationType.

query getSupportedQueries {
  __schema {
    queryType {
      fields{
        name
      }
    }
  }
}

The JSON response below shows the queries supported by the API.

{
  "data": {
    "__schema": {
      "queryType": {
        "fields": [
          {
            "name": "codeOfConduct"
          },
          {
            "name": "codesOfConduct"
          },
          {
            "name": "enterprise"
          },
          {
            "name": "enterpriseAdministratorInvitation"
          },
          {
            "name": "enterpriseAdministratorInvitationByToken"
          },
          {
            "name": "license"
          },
          {
            "name": "licenses"
          },
          {
            "name": "marketplaceCategories"
          },
          {
            "name": "marketplaceCategory"
          },
          {
            "name": "marketplaceListing"
          },
          {
            "name": "marketplaceListings"
          },
          {
            "name": "meta"
          },
          {
            "name": "node"
          },
          {
            "name": "nodes"
          },
          {
            "name": "organization"
          },
          {
            "name": "rateLimit"
          },
          {
            "name": "relay"
          },
          {
            "name": "repository"
          },
          {
            "name": "repositoryOwner"
          },
          .....
      }
    }
  }
}

#graphql #database #programming #developer

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Buddha Community

How model queries work in Django

How model queries work in Django

Welcome to my blog, hey everyone in this article we are going to be working with queries in Django so for any web app that you build your going to want to write a query so you can retrieve information from your database so in this article I’ll be showing you all the different ways that you can write queries and it should cover about 90% of the cases that you’ll have when you’re writing your code the other 10% depend on your specific use case you may have to get more complicated but for the most part what I cover in this article should be able to help you so let’s start with the model that I have I’ve already created it.

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let’s just get into this diagram that I made so in here:

Describe each parameter in Django querset

we’re making a simple query for the myModel table so we want to pull out all the information in the database so we have this variable which is gonna hold a return value and we have our myModel models so this is simply the myModel model name so whatever you named your model just make sure you specify that and we’re gonna access the objects attribute once we get that object’s attribute we can simply use the all method and this will return all the information in the database so we’re gonna start with all and then we will go into getting single items filtering that data and go to our command prompt.

Here and we’ll actually start making our queries from here to do this let’s just go ahead and run** Python manage.py shell** and I am in my project file so make sure you’re in there when you start and what this does is it gives us an interactive shell to actually start working with our data so this is a lot like the Python shell but because we did manage.py it allows us to do things a Django way and actually query our database now open up the command prompt and let’s go ahead and start making our first queries.

#django #django model queries #django orm #django queries #django query #model django query #model query #query with django

Elm Graphql: Autogenerate Type-safe GraphQL Queries in Elm

dillonkearns/elm-graphql  

Why use this package over the other available Elm GraphQL packages? This is the only one that generates type-safe code for your entire schema. Check out this blog post, Type-Safe & Composable GraphQL in Elm, to learn more about the motivation for this library. (It's also the only type-safe library with Elm 0.18 or 0.19 support, see this discourse thread).

I built this package because I wanted to have something that:

1. Gives you type-safe GraphQL queries (if it compiles, it's valid according to the schema),
2. Creates decoders for you in a seamless and failsafe way, and
3. Eliminates GraphQL features in favor of Elm language constructs where possible for a simpler UX (for example, GraphQL variables & fragments should just be Elm functions, constants, lets).

See an example in action on Ellie. See more end-to-end example code in the examples/ folder.

Overview

dillonkearns/elm-graphql is an Elm package and accompanying command-line code generator that creates type-safe Elm code for your GraphQL endpoint. You don't write any decoders for your API with dillonkearns/elm-graphql, instead you simply select which fields you would like, similar to a standard GraphQL query but in Elm. For example, this GraphQL query

query {
  human(id: "1001") {
    name
    homePlanet
  }
}

would look like this in dillonkearns/elm-graphql (the code in this example that is prefixed with StarWars is auto-generated)

import Graphql.Operation exposing (RootQuery)
import Graphql.SelectionSet as SelectionSet exposing (SelectionSet)
import StarWars.Object
import StarWars.Object.Human as Human
import StarWars.Query as Query
import StarWars.Scalar exposing (Id(..))


query : SelectionSet (Maybe HumanData) RootQuery
query =
    Query.human { id = Id "1001" } humanSelection


type alias HumanData =
    { name : String
    , homePlanet : Maybe String
    }


humanSelection : SelectionSet HumanData StarWars.Object.Human
humanSelection =
    SelectionSet.map2 HumanData
        Human.name
        Human.homePlanet

GraphQL and Elm are a perfect match because GraphQL is used to enforce the types that your API takes as inputs and outputs, much like Elm's type system does within Elm. elm-graphql simply bridges this gap by making your Elm code aware of your GraphQL server's schema. If you are new to GraphQL, graphql.org/learn/ is an excellent way to learn the basics.

After following the installation instructions to install the @dillonkearns/elm-graphql NPM package and the proper Elm packages (see the Setup section for details). Once you've installed everything, running the elm-graphql code generation tool is as simple as this:

npx elm-graphql https://elm-graphql.herokuapp.com --base StarWars --output examples/src

If headers are required, such as a Bearer Token, the --header flag can be supplied.

npx elm-graphql https://elm-graphql.herokuapp.com --base StarWars --output examples/src --header 'headerKey: header value'

Learning Resources

There is a thorough tutorial in the SelectionSet docs. SelectionSets are the core concept in this library, so I recommend reading through the whole page (it's not very long!).

The examples/ folder is another great place to start.

If you want to learn more GraphQL basics, this is a great tutorial, and a short read: graphql.org/learn/

My Elm Conf 2018 talk goes into the philosophy behind dillonkearns/elm-graphql

(Skip to 13:06 to go straight to the dillonkearns/elm-graphql demo).

• My 10-minute video tutorial on how to leverage Custom Scalars in elm-graphql using the Scalar Codecs feature.
• A Beginner's Guide to GraphQL with Elm by @martimatix
• Graphqelm: Optional Arguments in a Language Without Optional Arguments by @martimatix
• Comprehensive tutorial by the Hasura Team

If you're wondering why code is generated a certain way, you're likely to find an answer in the Frequently Asked Questions (FAQ).

There's a very helpful group of people in the #graphql channel in the Elm Slack. Don't hesitate to ask any questions about getting started, best practices, or just general GraphQL in there!

Setup

dillonkearns/elm-graphql generates Elm code that allows you to build up type-safe GraphQL requests. Here are the steps to setup dillonkearns/elm-graphql.

Add the dillonkearns/elm-graphql elm package as a dependency in your elm.json. You will also need to make sure that elm/json is a dependency of your project since the generated code has lots of JSON decoders in it.

elm install dillonkearns/elm-graphql
elm install elm/json

Install the @dillonkearns/elm-graphql command line tool through npm. This is what you will use to generate Elm code for your API. It is recommended that you save the @dillonkearns/elm-graphql command line tool as a dev dependency so that everyone on your project is using the same version.

npm install --save-dev @dillonkearns/elm-graphql
# you can now run it locally using `npx elm-graphql`,
# or by calling it through an npm script as in this project's package.json

Run the @dillonkearns/elm-graphql command line tool installed above to generate your code. If you used the --save-dev method above, you can simply create a script in your package.json like the following:

{
  "name": "star-wars-elm-graphql-project",
  "version": "1.0.0",
  "scripts": {
    "api": "elm-graphql https://elm-graphql.herokuapp.com/api --base StarWars"
  }

With the above in your package.json, running npm run api will generate dillonkearns/elm-graphql code for you to call in ./src/StarWars/. You can now use the generated code as in this Ellie example or in the examples folder.

Subscriptions Support

You can do real-time APIs using GraphQL Subscriptions and dillonkearns/elm-graphql. Just wire in the framework-specific JavaScript code for opening the WebSocket connection through a port. Here's a live demo and its source code. The demo server is running Elixir/Absinthe.

Contributors

Thank you Mario Martinez (martimatix) for all your feedback, the elm-format PR, and for the incredible logo design!

Thank you Mike Stock (mikeastock) for setting up Travis CI!

Thanks for the reserved words pull request @madsflensted!

A huge thanks to @xtian for doing the vast majority of the 0.19 upgrade work! :tada:

Thank you Josh Adams (@knewter) for the code example for Subscriptions with Elixir/Absinthe wired up through Elm ports!

Thank you Romario for adding OptionalArgument.map!

Thank you Aaron White for your pull request to improve the performance and stability of the elm-format step! 🎉

Roadmap

All core features are supported. That is, you can build any query or mutation with your dillonkearns/elm-graphql-generated code, and it is guaranteed to be valid according to your server's schema.

dillonkearns/elm-graphql will generate code for you to generate subscriptions and decode the responses, but it doesn't deal with the low-level details for how to send them over web sockets. To do that, you will need to use custom code or a package that knows how to communicate over websockets (or whichever protocol) to setup a subscription with your particular framework. See this discussion for why those details are not handled by this library directly.

I would love to hear feedback if you are using GraphQL Subscriptions. In particular, I'd love to see live code examples to drive any improvements to the Subscriptions design. Please ping me on Slack, drop a message in the #graphql channel, or open up a Github issue to discuss!

I would like to investigate generating helpers to make pagination simpler for Connections (based on the Relay Cursor Connections Specification). If you have ideas on this chime in on this thread.

See the full roadmap on Trello.

---

Author: dillonkearns
Source Code: https://github.com/dillonkearns/elm-graphql
License: View license

#graphql 

Google Reveals "What is being Transferred” in Transfer Learning

Recently, researchers from Google proposed the solution of a very fundamental question in the machine learning community — What is being transferred in Transfer Learning? They explained various tools and analyses to address the fundamental question.

The ability to transfer the domain knowledge of one machine in which it is trained on to another where the data is usually scarce is one of the desired capabilities for machines. Researchers around the globe have been using transfer learning in various deep learning applications, including object detection, image classification, medical imaging tasks, among others.

#developers corner #learn transfer learning #machine learning #transfer learning #transfer learning methods #transfer learning resources

What is a GraphQL query? GraphQL query examples using Apollo Explorer

How to execute GraphQL queries

We know what queries look like and we know what to expect in response when we write them. The next question is: how do we execute them?

It’s important to know that since GraphQL queries are just plain strings, we can use a variety of approaches to fetch data. Among the many options, some that come to mind are:

• curl
• fetch
• GraphQL client libraries (like Apollo Client)

#graphql #graphql query #apollo explorer

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