Trait CustomDataType 

pub trait CustomDataType: DataType {
    const TYPE_TAG: &'static str;
}

A trait for user-defined custom data types.

Custom types are stored as type-erased CustomValue inside Value::Custom. The TYPE_TAG constant uniquely identifies the type and must be stable across versions.

Ordering contract

For custom types used with range filters (Gt, Lt, Ge, Le) or ORDER BY, the Encode output must be order-preserving: if a < b, then a.encode() < b.encode() lexicographically. Equality filters (Eq, Ne, In) only require canonical encoding.

Required Associated Constants

const TYPE_TAG: &'static str

Unique string identifier for this type (e.g., "principal", "role").

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors