Struct MetadataMap

pub(crate) struct MetadataMap(BTreeMap<String, Bytes>);

Our Proto implementation, Prost, cannot handle unrecognized fields. This means that unexpected data will be dropped at deserialization time, which means that we can’t reliably roundtrip data from future versions of the code, which causes trouble during upgrades and at other times.

This type works around the issue by defining an unstructured metadata map. Keys are expected to be well-known strings defined in the code; values are bytes, expected to be encoded protobuf. (The association between the two is lightly enforced with the affiliated MetadataKey type.) It’s safe to add new metadata keys in new versions, since even unrecognized keys can be losslessly roundtripped. However, if the metadata is not safe for the old version to ignore – perhaps it needs to be kept in sync with some other part of the struct – you will need to use a more heavyweight migration for it.

Tuple Fields

0: BTreeMap<String, Bytes>

Implementations

impl MetadataMap

pub fn is_empty(&self) -> bool

Returns true iff no metadata keys have been set.

pub fn set<V: RustType<P>, P: Message>( &mut self, key: MetadataKey<V, P>, value: V, )

Serialize and insert a new key into the map, replacing any existing value for the key.

pub fn get<V: RustType<P>, P: Message + Default>( &self, key: MetadataKey<V, P>, ) -> Option<V>

Deserialize a key from the map, if it is present.

Trait Implementations

impl Clone for MetadataMap

fn clone(&self) -> MetadataMap

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for MetadataMap

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for MetadataMap

fn default() -> MetadataMap

Returns the “default value” for a type.

impl Hash for MetadataMap

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

Feeds this value into the given Hasher.

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

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for MetadataMap

fn cmp(&self, other: &MetadataMap) -> Ordering

This method returns an Ordering between self and other.

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

where Self: Sized,

Compares and returns the maximum of two values.

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

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for MetadataMap

fn eq(&self, other: &MetadataMap) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for MetadataMap

fn partial_cmp(&self, other: &MetadataMap) -> Option<Ordering>

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

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

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

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

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

impl RustType<BTreeMap<String, Bytes>> for MetadataMap

fn into_proto(&self) -> BTreeMap<String, Bytes>

Convert a Self into a Proto value.

fn from_proto(proto: BTreeMap<String, Bytes>) -> Result<Self, TryFromProtoError>

Consume and convert a Proto back into a Self value.

fn into_proto_owned(self) -> Proto

A zero clone version of Self::into_proto that types can optionally implement, otherwise, the default implementation delegates to Self::into_proto.

impl Serialize for MetadataMap

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for MetadataMap

impl StructuralPartialEq for MetadataMap