Modify existing schema

Add

We can add types and rules to an existing schema by running new define statements to the same database as usual.

The define statements are idempotent. By sending the same define query twice or more times, the resulting schema must be achieved as if we send it only once. So types and/or rules will not be duplicated.

A separate define statement for a new type or a rule can be sent as a define query. Alternatively, the statement can be added to the define statement of the existing schema and sent together. Only new types and/or rules will be added in this case. If we change the name (label) of the existing type or rule in the existing schema and then send it as a define query, then the changed type or rule will be processed as a new one.

Define queries are idempotent.

Running the same define query a second time shall not produce any changes to the database schema.

Running a modified version of an already executed schema definition query can add concepts to the schema but mostly can’t modify existing ones. TypeQL schema statements do NOT replace existing type definitions but add missing parts.

Two notable exceptions are:

rules (defining a new rule with an existing label/name will replace the existing rule completely), and
annotations, like the @key keyword (which we can remove by redefining attribute ownership without the annotation).

Delete

Use the undefine keyword to remove the definition of a type or its association with other types from the schema.

Don’t forget to commit after executing an undefine statement. Otherwise, any changes are NOT committed to a database.

Undefine a type

To delete a user-defined type from a schema use the keyword undefine with the label of a type to delete and sub keyword, followed by the supertype (direct or not) of the deleted type.

undefine subject sub entity;

Types with existing subtypes or instances can’t be undefined. Undefine any subtypes and delete any data instances of a type to be able to undefine it.

Undefine an attribute’s association

We can undefine the association that a type has with an attribute.

undefine subject owns credential;

The query above removes ownership of the attribute type credential from the entity type subject. Therefore, instances of the subject type will no longer be able to have ownership over instances of the credential type.

It’s important to note that if we add the sub keyword to the label at the beginning: undefine [label] sub [type], owns [attributes' label]; it undefines the label type itself, rather than just its association with the attribute type.

For example, undefine subject sub entity, owns credential; will delete the subject entity type from the schema. The ownership of the credential attribute type by the subject entity type will also be removed, but the credential attribute type will continue to exist. To undefine it from a schema, use undefine credential sub attribute;.

Undefine a relation

Undefining a relation type undefines all of its roles. Therefore, when a relation type is undefined any types that were playing roles in that relation type will no longer play those roles. Given a change-request relation type, we can undefine it as shown below.

undefine

change-request sub relation;

Undefine a supertype

When a type to be undefined is a supertype to some other types, we must first undefine all its subtypes before undefining the supertype itself. We can use the same query to delete both the supertype and all its subtypes.

undefine

object sub entity;
resource sub object;

If we are using the same query to undefine supertype and all its subtypes, we need to make sure to use the supertype label in the subtypes undefine statements (directly right from the sub keyword). Otherwise, query will fail as invalid, due to one of the deleted types having subtypes.

Undefine a rule

Rules, like any other schema members, can be undefined. Hence, to delete a rule, use the undefine rule keywords and refer to the rule by its label. For example:

undefine rule add-view-permission;

Rename a type

To rename a type (to change its label), use the TypeDB Studio or TypeDB Driver API: Rust, Python, Java, Node.js.

Modify a rule

To modify a rule, define a new rule with the same label. It will overwrite the existing rule upon commit.

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