Abi

Updates

When modifying custom types, you may encounter the following error

abi update failed: can’t add a non-nullable ….

This occurs in scenarios like the following:

type Foo {
    a: int;
}

Start the server

greycat serve

Kill the server

Now, modify the type by adding a new non-nullable field:

type Foo {
    a: int;
    b: int;
}

Restart the server:

greycat serve

Ensuring Graph Integrity

If an object of this type already exists in the graph (or could exist), adding a new non-nullable attribute would render those objects incompatible with the updated ABI. Since there is no guarantee that the new attribute has a valid value for all existing objects, this update is disallowed.

How to Resolve This

• If you’re working in a development environment, you can delete the /gcdata directory and reimport your data.
• If deletion is not an option, any new attributes must be declared as nullable: This will work;

type Foo {
    a: int;
    b: int?;
}

Deleting existing attributes is allowed without restrictions. The limitation applies only to adding non-nullable fields to existing types.

Types are not always used to be stored in the graph, for that reason we have @volatile pragma to solve this issue.