Struct Cursor 

pub struct Cursor {
    pub ts: i64,
    pub node: u32,
    pub seq: u64,
    pub row: u32,
}

Where the previous page stopped.

Keyset, not offset, and not for tidiness: offset: 20000 forces the engine to find and discard twenty thousand rows on every page, which turns the early exit below into a full scan and makes the last page the most expensive one. It is also wrong on a store that is still being written to — a batch arriving between two pages shifts every row down and the reader sees a row twice or never.

This is the sort key of the last row returned, so “the next page” is “everything that sorts after this”, which is exact whatever else has landed meanwhile. (node, seq) identifies the block globally with no coordination (see block::node_id) and row is its offset inside it, so the key is intrinsic to the record rather than to the query that found it.

Rendered as ts.node.seq.row, in decimal, on purpose: an agent reading a response can tell what it is holding, and a human debugging a stuck reader can tell where it stopped.

Fields

ts: i64

node: u32

seq: u64

row: u32

Implementations

impl Cursor

fn key(&self) -> Reverse<(i64, u32, u64, u32)>

Descending: newest first, and for rows sharing a nanosecond, the higher-numbered block and row first. Any total order would do; what matters is that it is total, so no row can hide in a tie.

Trait Implementations

impl Clone for Cursor

fn clone(&self) -> Cursor

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Cursor

impl Debug for Cursor

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

Formats the value using the given formatter.

impl Display for Cursor

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

Formats the value using the given formatter.

impl Eq for Cursor

impl FromStr for Cursor

type Err = String

The associated error which can be returned from parsing.

fn from_str(s: &str) -> Result<Cursor, String>

Parses a string s to return a value of this type.

impl PartialEq for Cursor

fn eq(&self, other: &Cursor) -> 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 StructuralPartialEq for Cursor