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CRUD Mutations

CRUD, or "Create, Read, Update, Delete", is a common paradigm in data manipulation APIs; "CRUD Mutations" refer to all but the "R". PostGraphile will automatically add CRUD mutations to the schema for each table that has the relevant database permissions.

Designing mutations

CRUD mutations can easily be disabled by disabling the create, update and delete behaviors in your preset:

graphile.config.mjs
export default {
// ...
schema: {
defaultBehavior: "-insert -update -delete",
},
};

You might do this if you prefer to define all of your mutations yourself (e.g. with custom mutations).

It's a common misconception for people unfamiliar with PostGraphile that its main feature is the CRUD mutations. In actuality, a very significant portion of users (including the maintainer) hardly ever use the CRUD mutations. PostGraphile encourages you to write the best GraphQL API that you can, so before designing your mutations we strongly recommend that you read Marc-André Giroux's excellent GraphQL Mutation Design: Anemic Mutations article.

PostGraphile gives you a lot of ways to define your own mutations (from database functions, to schema extensions, to custom plugins), so you can pick whichever pattern you and your team are most comfortable with.

note

You might be wondering, "What value do users see in PostGraphile if not the CRUD mutations?" These users typically recognize PostGraphile's significant efficiency gains in the query schema meaning they can handle larger amounts of traffic and don't need to concern themselves with the complexities of caches and cache invalidation for a lot longer. There's also the consistency afforded through (and time saved by) autogeneration; the GraphQL best practices enabled by the out-of-the box schema; and the easy schema-wide changes via the plugin and behavior systems. These are just some of the well-known key features of PostGraphile.

CRUD mutation fields

Using the users table from the parent article, depending on the PostGraphile settings you use (and the permissions you've granted), you might get the following mutations:

  • createUser - Creates a single User. See example.
  • updateUser - Updates a single User using its globally unique id and a patch.
  • updateUserById - Updates a single User using a unique key and a patch. See example.
  • updateUserByUsername - Updates a single User using a unique key and a patch.
  • deleteUser - Deletes a single User using its globally unique id.
  • deleteUserById - Deletes a single User using a unique key. See example.
  • deleteUserByUsername - Deletes a single User using a unique key.

The update and delete mutations are created only if the table contains a primary key column.

You also get the following query fields ("Read"):

  • user - Returns a single User using its globally unique ID.
  • userById - Reads a single User using its globally unique ID.
  • userByUsername - Reads a single User using its unique username.
  • allUsers - Returns a connection enabling pagination through a set of (visible) User.

Examples

# Create a User and get back details of the record we created
mutation {
createUser(
input: { user: { id: 1, name: "Bilbo Baggins", username: "bilbo" } }
) {
user {
id
name
username
createdAt
}
}
}

# Update Bilbo using the user.id primary key
mutation {
updateUserById(
input: { id: 1, userPatch: { about: "An adventurous hobbit" } }
) {
user {
id
name
username
about
createdAt
}
}
}

# Delete Bilbo using the unique user.username column and return the mutation ID
mutation {
deleteUserByUsername(input: { username: "bilbo" }) {
deletedUserId
}
}

If mutations don't show up...

First of all, check for errors being output from your PostGraphile server. If there are no errors, here's some reasons that mutations might not show up in the generated schema:

  • Your behaviors (e.g. defaultBehavior: "-create -update -delete" or @behavior -create -update -delete smart comments on the tables) may be disabling them
  • Insufficient permissions on the tables
  • Tables not in an exposed schema
  • Views instead of tables
  • Missing primary keys (though 'create' mutations will still be added in this case)
  • If you only see mutations using primary key: You might be using the PrimaryKeyMutationsOnlyPlugin

If you're new to GraphQL, perhaps you're looking in the wrong place? In Ruru (the GraphiQL interface), open the docs on the right and go to the root. Select the Mutation type to see the available mutations. If you try to execute a mutation (e.g. using autocomplete) you must use the mutation operation type when composing the request:

mutation {
createThing...
}

otherwise GraphQL will interpret the request as a query.