Struct Watermark 

#[non_exhaustive]
pub struct Watermark {
    pub cursor: Option<Bytes>,
    pub checkpoint: Option<u64>,
}

Progress marker for a query scan. Carried on every response frame, whether or not the frame delivers a matching item. Watermarks never regress in the requested ordering, but consecutive frames may carry the same watermark when additional work does not advance the safe resume frontier.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

cursor: Option<Bytes>

Opaque cursor at this scan position. Set on every watermark. Use as options.after (ascending) or options.before (descending) on the next request to resume from here. The most recently received cursor is always the safe resume point.

checkpoint: Option<u64>

The inclusive boundary checkpoint that the scan has fully covered within the request’s effective interval, in the request’s ordering direction: an ascending scan has emitted every matching item in the interval at checkpoints <= checkpoint (strictly greater ones may still hold matches); a descending scan has emitted every matching item in the interval at checkpoints >= checkpoint. This boundary never regresses in the scan direction, but it may repeat while the cursor advances.

Unset until the scan’s first checkpoint is fully covered. For example, a scan resumed from a cursor that lands mid-checkpoint leaves this unset until the next checkpoint boundary in the scan direction is fully covered. A watermark still has a valid resume cursor while this field is unset.

Implementations

impl Watermark

pub const CURSOR_FIELD: &'static MessageField

pub const CHECKPOINT_FIELD: &'static MessageField

impl Watermark

pub fn path_builder() -> WatermarkFieldPathBuilder

impl Watermark

pub const fn const_default() -> Self

pub fn cursor_opt(&self) -> Option<&[u8]>

If cursor is set, returns Some with the value; otherwise returns None.

pub fn set_cursor<T: Into<Bytes>>(&mut self, field: T)

Sets cursor with the provided value.

pub fn with_cursor<T: Into<Bytes>>(self, field: T) -> Self

Sets cursor with the provided value.

pub fn checkpoint_opt_mut(&mut self) -> Option<&mut u64>

If checkpoint is set, returns Some with a mutable reference to the value; otherwise returns None.

pub fn checkpoint_mut(&mut self) -> &mut u64

Returns a mutable reference to checkpoint. If the field is unset, it is first initialized with the default value.

pub fn checkpoint_opt(&self) -> Option<u64>

If checkpoint is set, returns Some with the value; otherwise returns None.

pub fn set_checkpoint(&mut self, field: u64)

Sets checkpoint with the provided value.

pub fn with_checkpoint(self, field: u64) -> Self

Sets checkpoint with the provided value.

impl Watermark

pub fn cursor(&self) -> &[u8]

Returns the value of cursor, or the default value if cursor is unset.

pub fn checkpoint(&self) -> u64

Returns the value of checkpoint, or the default value if checkpoint is unset.

Trait Implementations

impl Clone for Watermark

fn clone(&self) -> Watermark

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Watermark

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

Formats the value using the given formatter.

impl Default for Watermark

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Watermark

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Hash for Watermark

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 Message for Watermark

fn encoded_len(&self) -> usize

Returns the encoded length of the message without a length delimiter.

fn clear(&mut self)

Clears the message, resetting all fields to their default.

fn encode(&self, buf: &mut impl BufMut) -> Result<(), EncodeError>

where Self: Sized,

Encodes the message to a buffer.

fn encode_to_vec(&self) -> Vec<u8>

where Self: Sized,

Encodes the message to a newly allocated buffer.

fn encode_length_delimited( &self, buf: &mut impl BufMut, ) -> Result<(), EncodeError>

where Self: Sized,

Encodes the message with a length-delimiter to a buffer.

fn encode_length_delimited_to_vec(&self) -> Vec<u8>

where Self: Sized,

Encodes the message with a length-delimiter to a newly allocated buffer.

fn decode(buf: impl Buf) -> Result<Self, DecodeError>

where Self: Default,

Decodes an instance of the message from a buffer.

fn decode_length_delimited(buf: impl Buf) -> Result<Self, DecodeError>

where Self: Default,

Decodes a length-delimited instance of the message from the buffer.

fn merge(&mut self, buf: impl Buf) -> Result<(), DecodeError>

where Self: Sized,

Decodes an instance of the message from a buffer, and merges it into self.

fn merge_length_delimited(&mut self, buf: impl Buf) -> Result<(), DecodeError>

where Self: Sized,

Decodes a length-delimited instance of the message from buffer, and merges it into self.

impl MessageFields for Watermark

const FIELDS: &'static [&'static MessageField]

impl PartialEq for Watermark

fn eq(&self, other: &Watermark) -> 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 Serialize for Watermark

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 Watermark

impl StructuralPartialEq for Watermark