mirror of
https://github.com/hasura/graphql-engine.git
synced 2024-12-17 04:24:35 +03:00
69 lines
2.5 KiB
ReStructuredText
69 lines
2.5 KiB
ReStructuredText
|
How Hasura GraphQL engine works
|
|||
|
|
===============================
|
|||
|
|
|
|||
|
|
.. contents:: Table of contents
|
|||
|
|
:backlinks: none
|
|||
|
|
:depth: 1
|
|||
|
|
:local:
|
|||
|
|
|
|||
|
|
Given a Postgres database, Hasura GraphQL engine can automatically generate a GraphQL schema and process GraphQL
|
|||
|
|
queries, subscriptions and mutations. Here’s what Hasura GraphQL engine does under the hood.
|
|||
|
|
|
|||
|
|
Schema generation
|
|||
|
|
-----------------
|
|||
|
|
|
|||
|
|
Hasura GraphQL engine automatically generates GraphQL schema components when you track a
|
|||
|
|
Postgres table/view in Hasura and create relationships between them.
|
|||
|
|
|
|||
|
|
Tables
|
|||
|
|
^^^^^^
|
|||
|
|
|
|||
|
|
When you track a Postgres table in Hasura GraphQL engine, it automatically generates the following for it:
|
|||
|
|
|
|||
|
|
- A GraphQL type definition for the table
|
|||
|
|
- A Query field with ``where``, ``order_by``, ``limit`` and ``offset`` arguments
|
|||
|
|
- A Subscription field with ``where``, ``order_by``, ``limit`` and ``offset`` arguments
|
|||
|
|
- An Insert mutation field with ``on_conflict`` argument that supports upsert and bulk inserts
|
|||
|
|
- An Update mutation field with ``where`` argument that supports bulk updates
|
|||
|
|
- A Delete mutation field with ``where`` argument that supports bulk deletes
|
|||
|
|
|
|||
|
|
Views
|
|||
|
|
^^^^^
|
|||
|
|
|
|||
|
|
When you track a Postgres view in Hasura GraphQL engine, it automatically generates the following for it:
|
|||
|
|
|
|||
|
|
- A GraphQL type definition for the view
|
|||
|
|
- A Query field with ``where``, ``order_by``, ``limit`` and ``offset`` arguments
|
|||
|
|
- A Subscription field with ``where``, ``order_by``, ``limit`` and ``offset`` arguments
|
|||
|
|
|
|||
|
|
Essentially Hasura GraphQL engine does the same thing it would do for a table, but without creating the insert, update
|
|||
|
|
and delete mutations.
|
|||
|
|
|
|||
|
|
Relationships
|
|||
|
|
^^^^^^^^^^^^^
|
|||
|
|
When you create a relationship between a table/view with another table/view in Hasura GraphQL engine, it does the
|
|||
|
|
following:
|
|||
|
|
|
|||
|
|
- Augments the type of the table/view by adding a reference to the nested type to allow fetching nested objects.
|
|||
|
|
- Augments the ``where`` and ``order_by`` clauses to allow filtering and sorting based on nested objects.
|
|||
|
|
|
|||
|
|
Resolvers
|
|||
|
|
---------
|
|||
|
|
|
|||
|
|
Hasura GraphQL engine does not have any resolvers. The Hasura GraphQL engine is actually a compiler that compiles
|
|||
|
|
your GraphQL query into an SQL query.
|
|||
|
|
|
|||
|
|
Hasura's GraphQL syntax is also optimized to expose the power of the underlying SQL so that you can make powerful
|
|||
|
|
queries via GraphQL.
|
|||
|
|
|
|||
|
|
Metadata
|
|||
|
|
--------
|
|||
|
|
|
|||
|
|
All the information required for schema generation is stored by Hasura GraphQL engine as metadata in a specific
|
|||
|
|
Postgres schema in the database. See :doc:`metadata schema <metadata-schema>` for more details.
|
|||
|
|
|
|||
|
|
.. toctree::
|
|||
|
|
:maxdepth: 1
|
|||
|
|
:hidden:
|
|||
|
|
|
|||
|
|
Metadata schema <metadata-schema>
|