Struct RowIdGenerator

pub struct RowIdGenerator {
    base: SystemTime,
    last_timestamp_ms: i64,
    vnode_bit: u32,
    vnodes: Vec<VirtualNode>,
    vnodes_index: u16,
    sequence: u16,
}

RowIdGenerator generates unique row ids using snowflake algorithm as following format:

timestamp	vnode & sequence
41 bits	22 bits

The vnode part can occupy 10..=15 bits, which is determined by the vnode count. Thus, the sequence part will occupy 7..=12 bits. See bit_for_vnode for more details.

Fields

base: SystemTime

Specific base timestamp using for generating row ids.

last_timestamp_ms: i64

Last timestamp part of row id, based on base.

vnode_bit: u32

The number of bits used for vnode.

vnodes: Vec<VirtualNode>

Virtual nodes used by this generator.

vnodes_index: u16

Current index of vnodes.

sequence: u16

Last sequence part of row id.

Implementations

impl RowIdGenerator

pub fn new( vnodes: impl IntoIterator<Item = VirtualNode>, vnode_count: usize, ) -> Self

Create a new RowIdGenerator with given virtual nodes and vnode count.

fn sequence_upper_bound(&self) -> u16

The upper bound of the sequence part, exclusive.

fn try_update_timestamp(&mut self)

Update the timestamp, so that the millisecond part of row id is always increased.

This method will immediately return if the timestamp is increased or there’s remaining sequence for the current millisecond. Otherwise, it will spin loop until the timestamp is increased.

fn next_row_id_in_current_timestamp(&mut self) -> Option<RowId>

Generate a new RowId. Returns None if the sequence reaches the upper bound of current timestamp, and try_update_timestamp should be called to update the timestamp and reset the sequence. After that, the next call of this method always returns Some.

fn gen_iter(&mut self) -> impl Iterator<Item = RowId> + '_

Returns an infinite iterator that generates RowIds.

pub fn next_batch(&mut self, length: usize) -> Vec<RowId>

Generate a sequence of RowIds. Compared to next, this method is more efficient as it only checks the timestamp once before generating the first RowId, instead of doing that every RowId.

This may block for a while if too many IDs are generated in one millisecond.

pub fn next(&mut self) -> RowId

Generate a new RowId.

This may block for a while if too many IDs are generated in one millisecond.

Trait Implementations

impl Debug for RowIdGenerator

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

Formats the value using the given formatter.