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Modelling guide

A cruddl project consists of one or multiple GraphQL schema files and, optionally, metadata files in JSON or YAML format. A simple example can look like this:

import { Project } from 'cruddl';

const project = new Project([
    {
        name: 'schema.graphqls',
        body: `
        type Order @rootEntity {
          orderNumber: String
        }
    `,
    },
    {
        name: 'permission-profiles.json',
        body: JSON.stringify({
            permissionProfiles: {
                default: {
                    permissions: [
                        {
                            roles: ['users'],
                            access: 'readWrite',
                        },
                    ],
                },
            },
        }),
    },
]);

The file schema.graphqls contains type definitions while permission-profiles.json provides metadata (in this case, to grant unrestricted access users with the "users" role). The two file formats are distinguished by the extension of the name.

In this example, we define one type Order with a scalar field. This project already allows to create, update, delete and read Order objects. See the api documentation on how the queries and mutations look like.

Four kinds of object types

In the example above, Order is decorated with the @rootEntity directive, which distinguishes it from the other kinds of type definitions: @childEntity, @entityExtension and @valueObject. We use this to map the features of a document database to the world of GraphQL.

Root entities

Root entity types are the equivalent of documents in a document database. They have an implicit, auto-generated id field that identifies a root entity uniquely and is used to update and delete existing root entities. All queries and mutations start on root entities - all other kinds of objects are only accessible via their parent root entity.

type Order @rootEntity {
    orderNumber: String
}

When updating root entities and you specify only a subset of its fields, the other fields are not touched.

Child entities

Child entities behave like collections within root entities. They also have an auto-generated id field and it is possible to create, update and delete individual child entities. In contrast to root entities, child entities are embedded within a root entity, another child entity or an entity extension. A @childEntity type can also only be used within a list type.

type OrderItem @childEntity {
    itemNumber: String
    quantity: Int
}

type Order @rootEntity {
    # ...
    items: [OrderItem]
}

As with root entities, if you omit fields when updating a child entity, those are kept as-is.

Entity extensions

Child entity types can only be used within list types. To group a set of fields into a single object within an entity, use entity extensions.

type PaymentInfo @entityExtension {
    creditCardNumber: String
    payPalToken: String
}

type Order @rootEntity {
    # ...
    paymentInfo: PaymentInfo
}

Entity extension can be used within root entities, child entities and other entity extensions. If you omit fields when updating an entity extension, those are kept as-is. Entity extensions are never null - if you omit it entirely, or an object was created before it was added, the field evaluates to an empty object.

Value objects

Value objects are treated as atomic values much like scalars are. They cannot be partially updated but are replaced completely on updates. If you omit fields on update, they are set to null. This is useful for types like addresses. They can also be used within lists.

type Address @valueObject {
    street: String
    postalCode: String
    city: String
}

type Order @rootEntity {
    # ...
    shippingAddress: Address
}

Value object types are the most basic kinds of types and can only have fields of scalar, enum or value object type.

Linking objects

Relations

Relations define links between root entities. Use the @relation directive to define the forward link and @relation(inverseOf: "otherFieldName") for the back link.

type Order @rootEntity {
    # ...
    customer: Customer @relation
}

type Customer @rootEntity {
    name: String
    orders: [Order] @relation(inverseOf: "customer")
}

The back link can be omitted. If you however only omit the inverseOf argument on the back link, this creates two independent relations - one from customers to orders, and one from orders to customers. The cardinality of relations is determined by the field types. In this case, customer is of type Customer, but the inverse field - orders has a list type, resulting in a n-to-1 relation from orders to customers.

In ArangoDB, relations are stored in an edge collection with the name orders_customer (the plural of the source object combined with the field name).

onDelete actions

When a root entity is deleted, all related edges are deleted as well, but the related objects are left untouched. Forward relations (@relation without an inverseOf argument) can specify the onDelete argument to change this default behavior.

If onDelete: RESTRICT is configured, deletion is prevented if there are still objects linked with this relation. The related objects or the relations need to be deleted before the object can be deleted. This can either be done in its own operation or as a separate mutation field in the same operation that comes before the delete mutation field. On self-recursive relations (e.g. to child objects of the same type), you can also specify the parent and child ids in one deleteObjects or deleteAllObjects mutation.

If onDelete: CASCADE is configured, objects in this relation will be deleted alongside the object itself. If the related object has relations with onDelete: CASCADE, those will be deleted as well. This mode cannot be used recursively; it is a validation error in the model if a recursion is detected. It also can only be used on 1-to-n and m-to-n relations.

References

References allow to link to a root entity from any field, not only from another root entity. In contrast to relations, it is however not possible to navigate from the referenced object to the referencing object.

References are built from regular scalar fields that hold key, e.g. countryISOCode of type String. To upgrade this to a reference, you need to define a referenced root entity with a dedicated key field (e.g. Country.isoCode), and then use @reference to link them:

type Country @rootEntity {
    isoCode: String @key
    name: String
}

type Address @valueObject {
    # ...
    countryISOCode: String
    country: Country @reference(keyField: "countryISOCode")
}

In the data base, only countryISOCode will be stored, and you can use the field in normal way (setting, updating, filtering, sorting querying), In addition, you will be able to query the field country:

{
    Company(name: "AEB") {
        address {
            countryISOCode
            country {
                isoCode
                name
            }
        }
    }
}

The referenced country will be looked on demand. If the referenced object does not exist, it will be null ( though countryISOCode will still result in its value). You can think of references as more of an API feature than a modelling feature.

You can omit the argument keyField on the @reference directive. In the database, it will be stored with the name of the reference field. This variant is deprecated and should no longer be used.

Collect fields

With the @collect directive, you can define fields that are not persisted but rather compute their value when queried, based on other fields. It allows you to follow a path of relations, child entities and other fields, collect these values and optionally apply aggregations on them.

Basics

You can use @collect to follow two relations and collect all inner entities:

type OrderItem @childEntity {
    itemNumber: String
}

type Order @rootEntity {
    items: [OrderItem]
}

type Shipment @rootEntity {
    orders: [Order] @relation
    allItems: [OrderItem] @collect(path: "orders.items")
}

The field allItems will return all items in all orders of a shipment. It will not be available for filtering or sorting and you will not be able to set it directly in create and update mutations.

The path can traverse an arbitrary number of fields. Only the objects of the last field will be returned, and the type of that last field needs to match the traversal field type (OrderItem in the example). References cannot yet be followed, but you can use other traversal fields in the path.

Flattening tree structure

If you have a root entity with a relation to itself, you can use a collect field to flatten the tree:

type HandlingUnit {
    childHandlingUnits: [HandlingUnit] @relation
    parentHandlingUnit: HandlingUnit @relation(inverseOf: "childHandlingUnits")

    allInnerHandlingUnits: [HandlingUnit] @collect(path: "childHandlingUnits{1,3}")
}

The field allInnerHandlingUnits will result in the direct children, their children, and their children (by default, in depth-first order). The first number (1) is the minimum depth (which can also be 0 to include the originating entity), and the second number (3) is the maximum depth. If you omit the maximum depth, the minimum depth will be used as maximum depth. It's not possible to entirely omit the maximum depth.

The minimum and maximum depth can only be specified on directly recursive relations. It is not possible to cycle through indirectly recursive relations, and child entities don't support this feature at all.

Null values

If you follow a field that can be null (e.g. a to-1 relation or a simple scalar field), the collection may include null values. However, it is not allowed to define a list field that could include null values. Therefore, you need to define an aggregation, e.g. DISTINCT to remove null values.

If you follow a list field on an object that is null (e.g. order.orderItems if order is null), this null object just won't contribute any items. The resulting list will not include null in this case.

Collecting scalar values

A collect path can also end in a scalar field. This however requires the use of an aggregator (see next section). Use the aggregator DISTINCT if you are interested in the individual field values (see next section).

Aggregating values

With the optional aggregate argument, you can perform an aggregation on all collected items. For example, this allows you to sum up numbers:

type OrderItem @childEntity {
    itemNumber: String
    quantity: Int
}

type Order @rootEntity {
    items: [OrderItem]
    totalQuantity: Int @collect(path: "items.quantity", aggregate: SUM)
}

The path can use all the features from above and also use other @collect fields (but not nested aggregations at the moment).

The following operators are supported:

Operator Description Supported Types Null values Result on empty list
COUNT Total number of items (including null) all types (last segment must be a list) included 0
SOME true if there are any items (including null) all types (last segment must be a list) included false
NONE true if the list is empty all types (last segment must be a list) included true
None
COUNT_NULL Number of items that are null all nullable types see description 0
COUNT_NOT_NULL Number of items that are not null all nullable types see description 0
SOME_NULL true if there are items that are null all nullable types see description false
SOME_NOT_NULL true if there are items that are not null all nullable types see description false
EVERY_NULL true if there are no items that are not null all nullable types see description true
NONE_NULL true if there are no items that are null all nullable types see description true
Numbers
MIN Minimum value (ignoring null) Int, Float, DateTime, LocalDate, LocalTime excluded null
MAX Maximum value (ignoring null) Int, Float, DateTime, LocalDate, LocalTime excluded null
SUM Sum (ignoring null) Int, Float excluded 0
AVERAGE Sum / Count (ignoring null) Int, Float excluded null
Boolean
COUNT_TRUE Number of items that are true Boolean ≙ false 0
COUNT_NOT_TRUE Number of items that are not true Boolean ≙ false 0
SOME_TRUE true if there are items that are true Boolean ≙ false false
SOME_NOT_TRUE true if there are items that are not true Boolean ≙ false false
EVERY_TRUE true if there are no items that are not true Boolean ≙ false true
NONE_TRUE true if there are no items that are true Boolean ≙ false true
Distinct
DISTINCT all non-null values without duplicates String, ID, child/root entities, and enums excluded []
COUNT_DISTINCT number of non-null values without duplicates String, ID, child/root entities, and enums excluded 0

Note that if a value is collected multiple times, it will be used multiple times by the aggregator (e.g. counted twice).In the future, it will be possible to a field with DISTINCT aggregation in another aggregation field. Note that if a value is collected multiple times, it will be used multiple times by the aggregator (e.g. counted twice). In the future, it will be possible to a field with DISTINCT aggregation in another aggregation field.

Restrictions

  • Reference fields can currently not be used in the collect path.
  • Aggregation fields can currently not be used in the collect path, including the DISTINCT operator.
  • Min/Max depth can currently not be specified on child entities or nested value objects.
  • Min/Max depth can currently not be specified for indirectly recursive relations.
  • The InMemoryAdapter currently does not support min/max depth.

Also, some possible performance optimizations are not implemented yet. For example, the DISTINCT operator is applied at the end of a collection and not as early as possible.

Permissions

cruddl provides a role-based permission system. Permission rules can be defined on root entities and on fields. For root entities, the permissions can also be made dependent on a special field within the object to implement multi-tenancy.

Currently, there are two ways to specify permissions: Via the @roles directive or via permission profiles. The @roles directive will be deprecated in the future, but currently it is needed for field-based permissions.

The basic example above already specified a permission profile default which is applied to all root entities without an explicit permissionProfile argument in the @rootEntity directive:

{
    "permissionProfiles": {
        "default": {
            "permissions": [
                {
                    "roles": ["users"],
                    "access": "readWrite"
                }
            ]
        }
    }
}

This profile grants unrestricted access for the "users" role. The roles of a user are take from the authContext property on the GraphQL context. The following permission profile "restricted" allows read access to all roles starting with "user" and provides full access to the role "admin":

{
    "permissionProfiles": {
        "restricted": {
            "permissions": [
                {
                    "roles": ["admin"],
                    "access": "readWrite"
                },
                {
                    "roles": ["user*"],
                    "access": "read"
                }
            ]
        }
    }
}

You can use this profile as follows:

type Order @rootEntity(permissionProfile: "restricted") {
    # ...
}

Permission profiles are looked up in all json/yaml files within the type's namespace. If not found there, the namespace tree is navigated upwards. Permission profiles can be shadowed (i.e. a profile can be defined in a parent and in a child namespace, and the child namespace wins), but this generates a warning. The permission profile default can be shadowed without warning, so you can have namespace-dependent default permission profiles.

If a role specifier in a permission profile starts with a forward slash (/), it is interpreted as a regular expression. Be careful to use the start-of-string and end-of-string anchors (^ and $) to match the whole role instead of just part of it. An example would be "/^supplier-([a-z]+)$/".

Field permissions

To set permissions on individual fields, you need to use the @roles directive. This will be changed in the future to also work with permission profiles.

type Customer @rootEntity {
    paymentInfo: PaymentInfo @roles(readWrite: ["support-privileged"], read: [])
}

Data-dependent permissions

Use restrictToAccessGroups for a data-dependent permission profile: grants unrestricted access for all roles. The following permission profile "restricted" allows read access to all roles starting with "user" and provides full access to the role "admin":

{
    "permissionProfiles": {
        "restricted": {
            "permissions": [
                {
                    "roles": ["admin"],
                    "access": "readWrite"
                },
                {
                    "roles": ["support-europe"],
                    "access": "read",
                    "restrictToAccessGroups": ["EUROPE"]
                },
                {
                    "roles": ["support-america"],
                    "access": "read",
                    "restrictToAccessGroups": ["NORTH_AMERICA", "SOUTH_AMERICA"]
                }
            ]
        }
    }
}

You can use this profile as follows:

type Order @rootEntity(permissionProfile: "restricted") {
    # ...
    accessGroup: OrderAccessGroup
}

enum OrderAccessGroup {
    EUROPE
    NORTH_AMERICA
    SOUTH_AMERICA
    RESTRICTED
}
  • Users with role "admin" can access all orders.
  • Users with role "support-europe" can only access orders where accessGroup has the value "EUROPE".
  • Users with role "support-america" can only access orders where accessGroup has the value "NORTH_AMERICA" or " SOUTH_AMERICA".
  • Users with role "support-america" and "support-europe" can only access orders where accessGroup has the value " EUROPE", "NORTH_AMERICA", or "SOUTH_AMERICA".

You can also dynamically assign role-dependent access groups using regular expressions and capturing groups. For example:

{
    "permissionProfiles": {
        "forwarders": {
            "roles": ["/^forwarder-(.+)$/"],
            "access": "readWrite",
            "restrictToAccessGroups": ["forwarded-by-$1", "forwarded-by-anyone"]
        }
    }
}

A user with roles forwarder-fast and forwarder-quick is granted access to objects with accessGroup forwarded-by-fast, and forwarded-by-quick, and forwarded-by-anyone.

Data-dependent permissions using multiple fields

If you need to restrict access depending on multiple fields, or you want to use a custom field instead of accessGroup, you can alternatively use the following more flexible feature.

{
    "permissionProfiles": {
        "restricted": {
            "permissions": [
                {
                    "roles": ["support"],
                    "access": "readWrite",
                    "restrictions": [
                        {
                            "field": "isTopSecret",
                            "value": false
                        }
                    ]
                },
                {
                    "roles": ["/^seller-(.+)$/"],
                    "access": "readWrite",
                    "restrictions": [
                        {
                            "field": "seller",
                            "valueTemplate": "$1"
                        }
                    ]
                },
                {
                    "roles": ["/^buyer-(.+)$/"],
                    "access": "readWrite",
                    "restrictions": [
                        {
                            "field": "buyer",
                            "valueTemplate": "$1"
                        }
                    ]
                }
            ]
        }
    }
}

Without restrictions or with an empty array, the role grants access to all root entities covered by the permission profile. Each item in the restrictions array applies a further restriction on the value of a field. Only if all restrictions are met in a root entity, the access will be granted. If you need an OR combination, use multiple permissions items with identical roles.

Each restriction applies to a single field. You can specify a dot-separated path to nested fields, but root entity boundaries cannot be crossed. In general, the restrictions of index field paths apply, too.

The simplest kind of restriction requires a specific field value ("value": "theValue"). If you used a regular expression for matching the roles, you can also spedify valueTemplate and use the capture groups, e.g. "valueTemplate": "value-$1".

If you supply the claims of a user's token, you can also restrict access to objects where the field's value equals this claim value (or any of the claim values, if the claim is an array), with "claim": "claimName".

Indices

cruddl supports index handling. During start up they are extracted from the schema and created or removed from the database.

Root entity index definition

Indices can be added to the @rootEntity directive:

type Order @rootEntity(indices: [{ fields: ["orderNumber"], unique: true}, { fields: [ "shippingAddress.country", "shippingAddress.postalCode"] }]) {
    # ...
}

Field index definition

Indices can also be directly attached to fields. Multi-field indices are not supported via field definition.

type Order @rootEntity {
    orderNumber: String @unique
    trackingNumber: String @index
    # ...
}

Index options (unique and sparse)

Aside from the field list, indices have two options: unique and sparse. The field directives only have the sparse option because @unique is its own directive.

  • If unique is set, a unique constraint is created. This constraint ensures that there are no two root entities with the same value for this field. The index cannot be created (the creation will fail) if there are already conflicting root entities, and following creations and updates will throw an error if the constraint would be violated through this change.

  • sparse determines whether null values will be included in the index. If the option is set to true, null values will be omitted. Regular indices are non-sparse by default, unique indices are sparse by default. Unique sparse indices allow the value null in at most one root entity. For non-unique indices, the sparse option reduces index size, but it disqualifies the index to be used in some cases. For example, a sparse index cannot be used for sorting unless there also is a filter that makes sure no null values can be returned (even if there are actually no null values currently in the database).

More field features

There are two additional directives you can use on fields: @defaultValue and @calcMutations.

Default values

When an object is created without specifying all fields, the unspecified fields will be set to null (scalars and value objects), {} (entity extensions), or [] (child entities).

You can add the @defaultValue directive to a field to change this behavior. The default value will be used during object creation if the field value is not specified. The directive does not affect existing objects. This still applies if you add a new field with the @defaultValue directive: only newly created objects will have the default value.

Be careful with specifying the field value exactly, because there are currently no typechecks for default values. For example, for fields of type Int, make sure you specify a number and not a string value:

type Delivery @rootEntity {
    isShipped: Boolean @defaultValue(value: false)
}

Calc mutations

If you add the @calcMutations directive to a scalar field, additional input fields will be available for the update mutations. These fields perform simple calculations like incrementing a value or appending a list item. Calc mutations are always executed within the transaction, so you can use this to e.g. update a number range without risk of race conditions.

For example, given the following type definition:

type NumberRange @rootEntity {
    name: String @key
    value: Int @calcMutations(operators: [ADD])
}

You can increment the value with a mutation like this:

mutation UpdateNumberRange {
    updateNumberRange(input: { name: "deliveries", value_add: 1 }) {
        value
    }
}

The following operators are available on numeric types (GraphQLInt, GraphQLInt53, GraphQLFloat, GraphQLDecimal1, GraphQLDecimal2 and GraphQLDecimal3);

  • MULTIPLY
  • DIVIDE
  • ADD
  • SUBTRACT
  • MODULO

The following operators are available on the type String:

  • APPEND
  • PREPEND

Scalar types

Text types

String

The String scalar type represents textual data, represented as UTF-8 character sequences. The String type is most often used by GraphQL to represent free-form human-readable text.

ID

The ID scalar type represents a unique identifier, often used to refetch an object or as key for a cache. The ID type appears in a JSON response as a String; however, it is not intended to be human-readable. When expected as an input type, any string (such as "4") or integer (such as 4) input value will be accepted as an ID.

I18nString

The I18nString scalar type represents an internationalized string.

Structurally, the I18nString type is equivalent to the StringMap type. Keys are ISO 639-1 language codes, and values are the localized strings. In the future, more specific features may be added to this type, so it is preferred over the "StringMap" type to represent internationalized strings.

Values are not additionally JSON-encoded or JSON-parsed, so e.g. pass a raw JSON object here instead of a JSON-representation of that object.

Numeric types

Int

The Int scalar type represents non-fractional signed whole numeric values. Int can represent values between -(2^31)and 2^31 - 1.

Float

The Float scalar type represents signed double-precision fractional values as specified by IEEE 754.

Int53

The Int53 scalar type represents non-fractional signed whole numeric values. Int53 can represent values between -( 2^53) and 2^53 - 1.

Values of this type are serialized as numbers in GraphQL and JSON representations. The numeric range of this type corresponds to the safe integer range of an IEEE 754 double precision binary floating-point value.

Decimal1, Decimal2, Decimal3

The Decimal1, Decimal2, and Decimal3 scalar types represent signed numeric values with up to 1, 2, or 3, respectively, decimal digits. All three types can represent values between -1000000000.0 and 1000000000.0.

Values of this type are serialized as numbers in GraphQL and JSON representations. The value is always rounded to the respective amount of decimal digit.

Date / Time types

DateTime

The DateTime scalar type represents a point in time in UTC, in a format specified by ISO 8601, such as 2007-12-03T10:15:30Z or 2007-12-03T10:15:30.123Z.

This scalar type rejects values without timezone specifier or with a timezone other than UTC. See also OffsetDateTime for a point in time with an explicit timezone offset, or LocalDate and LocalTime for values without timezone specifier.

The second part is added if not specified, e.g. 2007-12-03T12:34Z is converted to 2007-12-03T12:34:00Z. Second fraction digits are cut off at the nearest three-digit group, e.g. 2007-12-03T00:00:00.1234Z is converted to 2007-12-03T00:00:00.123400Z.

Values with leap seconds are shifted back by one second, but this behavior should not be relied upon.

LocalDate

The LocalDate scalar type represents a date without time zone in a format specified by ISO 8601, such as 2007-12-03.

LocalTime

The LocalTime scalar type represents a time without time zone in a format specified by ISO 8601, such as 10:15:30 or 17:05:03.521.

The valid range is between 00:00:00 and 23:59:59.999999999. 24:00 is not allowed to avoid bugs in clients that treat 24: 00 as 0:00.

The seconds part is cut off if it is zero, e.g. 12:34:00 is converted to 12:34. Second fraction digits are cut off at the nearest three-digit group, e.g. 00:00:00.1234 is converted to 00:00:00.123400.

Leap seconds can not be specified.

OffsetDateTime

The OffsetDateTime scalar type represents a point in time with a timezone offset, in a format specified by ISO 8601, such as 2007-12-03T10:15:30+01:00 or 2007-12-03T10:15:30.123Z.

Only use this type for timestamps that are inherently tied to a location and the timezone offset should be calculated eagerly. To only store a point in time, use DateTime.

The second part is added if not specified, e.g. 2007-12-03T12:34Z is converted to 2007-12-03T12:34:00Z. Offset specifier Z is accepted but will be converted to +00:00. Leap seconds are not supported.

Other types

Boolean

The Boolean scalar type represents true or false.

JSON

The JSON scalar type represents an arbitrary JSON value. This can be a string, number, boolean, array, or object.

Values are not additionally JSON-encoded or JSON-parsed, so e.g. pass a raw JSON object here instead of a JSON-representation of that object.

JSONObject

The JSONObject scalar type represents a JSON object type with arbitrary properties.

This is similar to the JSON scalar type but disallows arrays, strings, numbers, and booleans.

Values are not additionally JSON-encoded or JSON-parsed, so e.g. pass a raw JSON object here instead of a JSON-representation of that object.

StringMap

The StringMap scalar type consists of a JSON object with only strings as values.

This type can be used for key-value mappings where fetching keys without values or values without keys does not make sense. For arbitrary maps, the "JSONObject" type can be used instead.

Values are not additionally JSON-encoded or JSON-parsed, so e.g. pass a raw JSON object here instead of a JSON-representation of that object.

System fields

Root entities and child entities have the implicit fields id, createdAt and updatedAt (the latter two of type DateTime). They are managed by cruddl and cannot be overwritten.