Add docs for batching queries and mutations in a single request. (#6)

Support was added in graphql-rust/juniper#171
and asked about in graphql-rust/juniper#214.

Author: LegNeato

docs/SUMMARY.md

@@ -1,34 +1,34 @@
 # Summary
 
-* [Introduction](README.md)
-* [Quickstart](quickstart.md)
+- [Introduction](README.md)
+- [Quickstart](quickstart.md)
 
 ## Type System
 
-* [Defining objects](types/objects/defining_objects.md)
-    * [Complex fields](types/objects/complex_fields.md)
-    * [Using contexts](types/objects/using_contexts.md)
-    * [Error handling](types/objects/error_handling.md)
-* Other types
-  * [Enums](types/enums.md)
-  * [Interfaces](types/interfaces.md)
-  * [Input objects](types/input_objects.md)
-  * [Scalars](types/scalars.md)
-  * [Unions](types/unions.md)
-
+- [Defining objects](types/objects/defining_objects.md)
+  - [Complex fields](types/objects/complex_fields.md)
+  - [Using contexts](types/objects/using_contexts.md)
+  - [Error handling](types/objects/error_handling.md)
+- Other types
+  - [Enums](types/enums.md)
+  - [Interfaces](types/interfaces.md)
+  - [Input objects](types/input_objects.md)
+  - [Scalars](types/scalars.md)
+  - [Unions](types/unions.md)
 
 ## Schema
 
-* [Schemas and mutations](schema/schemas_and_mutations.md)
+- [Schemas and mutations](schema/schemas_and_mutations.md)
 
 ## Adding a server
 
-* [Rocket](servers/rocket.md)
-* [Iron](servers/iron.md)
+- [Rocket](servers/rocket.md)
+- [Iron](servers/iron.md)
 
 ## Advanced Topics
 
-* [Non-struct objects](advanced/non_struct_objects.md)
-* [Objects and generics](advanced/objects_and_generics.md)
-* [Context switching]
-* [Dynamic type system]
+- [Non-struct objects](advanced/non_struct_objects.md)
+- [Objects and generics](advanced/objects_and_generics.md)
+- [Context switching]
+- [Dynamic type system]
+- [Multiple operations per request](advanced/multiple_ops_per_request.md)

docs/advanced/multiple_ops_per_request.md

@@ -0,0 +1,71 @@
+# Multiple operations per request
+
+The GraphQL standard generally assumes there will be one server request for each client operation you want to perform (such as a query or mutation). This is conceptually simple but has the potential to be inefficent.
+
+Some client libraries such as [apollo-link-batch-http](https://www.apollographql.com/docs/link/links/batch-http.html) have added the ability to batch operations in a single HTTP request to save network round-trips and increase performance.
+
+Juniper's [`Rocket`](servers/rocket.md) and [`Iron`](servers/iron.md) server integrations support multiple operations in a single HTTP request using JSON arrays. This makes them compatible with client libraries that support batch operations without any special configuration.
+
+For the following GraphQL query:
+
+```graphql
+{
+  hero {
+    name
+  }
+}
+```
+
+The json data to POST to the server for an individual request would be:
+
+```json
+{
+  "query": "{hero{name}}"
+}
+```
+
+And the response would be of the form:
+
+```json
+{
+  "data": {
+    "hero": {
+      "name": "R2-D2"
+    }
+  }
+}
+```
+
+If you wanted to run the same query twice in a single HTTP request, the batched json data to POST to the server would be:
+
+```json
+[
+  {
+    "query": "{hero{name}}"
+  },
+  {
+    "query": "{hero{name}}"
+  }
+]
+```
+
+And the response would be of the form:
+
+```json
+[
+  {
+    "data": {
+      "hero": {
+        "name": "R2-D2"
+      }
+    }
+  },
+  {
+    "data": {
+      "hero": {
+        "name": "R2-D2"
+      }
+    }
+  }
+]
+```