Struct core_traits::Attribute

pub struct Attribute {
    pub value_type: ValueType,
    pub multival: bool,
    pub unique: Option<Unique>,
    pub index: bool,
    pub fulltext: bool,
    pub component: bool,
    pub no_history: bool,
}

A Mentat schema attribute has a value type and several other flags determining how assertions with the attribute are interpreted.

TODO: consider packing this into a bitfield or similar.

Fields

value_type: ValueType

The associated value type, i.e., :db/valueType?

multival: bool

true if this attribute is multi-valued, i.e., it is :db/cardinality :db.cardinality/many. false if this attribute is single-valued (the default), i.e., it is :db/cardinality :db.cardinality/one.

unique: Option<Unique>

None if this attribute is neither unique-value nor unique-identity.

Some(attribute::Unique::Value) if this attribute is unique-value, i.e., it is :db/unique :db.unique/value.

Unique-value means that there is at most one assertion with the attribute and a particular value in the datom store. Unique-value attributes can be used in lookup-refs.

Some(attribute::Unique::Identity) if this attribute is unique-identity, i.e., it is :db/unique :db.unique/identity.

Unique-identity attributes always have value type Ref.

Unique-identity means that the attribute is unique-value and that they can be used in lookup-refs and will automatically upsert where appropriate.

index: bool

true if this attribute is automatically indexed, i.e., it is :db/indexing true.

fulltext: bool

true if this attribute is automatically fulltext indexed, i.e., it is :db/fulltext true.

Fulltext attributes always have string values.

component: bool

true if this attribute is a component, i.e., it is :db/isComponent true.

Component attributes always have value type Ref.

They are used to compose entities from component sub-entities: they are fetched recursively by pull expressions, and they are automatically recursively deleted where appropriate.

no_history: bool

true if this attribute doesn't require history to be kept, i.e., it is :db/noHistory true.

Methods

impl Attribute

pub fn flags(&self) -> u8

Combine several attribute flags into a bitfield used in temporary search tables.

pub fn to_edn_value(&self, ident: Option<Keyword>) -> Value

Trait Implementations

impl Clone for Attribute

fn clone(&self) -> Attribute

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Attribute

fn fmt(&self, __arg_0: &mut Formatter) -> Result

Formats the value using the given formatter.

impl Eq for Attribute

impl Hash for Attribute

fn hash<__H: Hasher>(&self, __arg_0: &mut __H)

Feeds this value into the given [Hasher].

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given [Hasher].

impl Ord for Attribute

fn cmp(&self, __arg_0: &Attribute) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

impl PartialOrd for Attribute

fn partial_cmp(&self, __arg_0: &Attribute) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, __arg_0: &Attribute) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, __arg_0: &Attribute) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, __arg_0: &Attribute) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, __arg_0: &Attribute) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl PartialEq for Attribute

fn eq(&self, __arg_0: &Attribute) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, __arg_0: &Attribute) -> bool

This method tests for !=.

impl Default for Attribute

fn default() -> Attribute

Returns the "default value" for a type.