Add count GraphQL guide

docs/.vuepress/config.js

@@ -212,6 +212,7 @@ module.exports = {
             '/3.0.0-beta.x/guides/scheduled-publication',
             '/3.0.0-beta.x/guides/slug',
             '/3.0.0-beta.x/guides/send-email',
+            '/3.0.0-beta.x/guides/count-graphql',
           ],
         },
         {

docs/3.0.0-beta.x/guides/count-graphql.md

@@ -0,0 +1,79 @@
+# Count with GraphQL
+
+This guide explains how to count data with a GraphQL query.
+
+The count aggregation has some issues and this feature is also not available for Bookshelf (SQL databases).
+
+With this guide we will code our own count query.
+
+Here is the [GraphQL documentation](../plugins/graphql.md#customise-the-graphql-schema) we will use to achieve our goal.
+
+## Setup the application
+
+In this example, we will use a **Restaurant** API.
+
+Make sure your have a **Content Type** with some entries.
+
+## Create schema.grahql file
+
+To be able to add a new custom query (or mutation), we will have to create a `schema.grahql` file in your **Restaurant** API.
+
+**Path** — `./api/restaurant/config/schema.graphql`
+
+```js
+module.exports = {
+  query: ``,
+  resolver: {
+    Query: {},
+  },
+};
+```
+
+## Create count query
+
+The `count` query will call the [`count`](../concepts/services.md#core-services) service function of the **Restaurant** API.
+
+It needs a JSON object as params, so we will add a `where` options in the GraphQL query.
+
+**Path** — `./api/restaurant/config/schema.graphql`
+
+```js
+module.exports = {
+  query: `
+    restaurantsCount(where: JSON): Int!
+  `,
+  resolver: {
+    Query: {
+      restaurantsCount: {
+        description: 'Return the count of restaurants',
+        resolverOf: 'application::restaurant.restaurant.count',
+        resolver: async (obj, options, ctx) => {
+          return await strapi.api.restaurant.services.restaurant.count(options.where || {});
+        },
+      },
+    },
+  },
+};
+```
+
+And tada, you can now request the `count` of your Content Type.
+
+## Query example
+
+- Count all restaurants
+
+```
+{
+  restaurantsCount
+}
+```
+
+- Count all restaurants that have `_3rd` as district value.
+
+Based on the [FoodAdvisor](https://github.com/strapi/foodadvisor) restraurant model.
+
+```
+{
+  restaurantsCount(where: { district: "_3rd" })
+}
+```