Enum HummockIteratorUnion 

pub enum HummockIteratorUnion<D: HummockIteratorDirection, I1: HummockIterator<Direction = D>, I2: HummockIterator<Direction = D>, I3: HummockIterator<Direction = D> = PhantomHummockIterator<D>, I4: HummockIterator<Direction = D> = PhantomHummockIterator<D>> {
    First(I1),
    Second(I2),
    Third(I3),
    Fourth(I4),
}

The HummockIteratorUnion acts like a wrapper over multiple types of HummockIterator, so that the MergeIterator, which previously takes multiple different HummockIterators as input through Box<dyn HummockIterator>, can now wrap all its underlying HummockIterator over such HummockIteratorUnion, and the input type of the MergeIterator so that the input type of HummockIterator can be determined statically at compile time.

For example, in ForwardUserIterator, it accepts inputs from 4 sources for its underlying MergeIterator. First, the shared buffer replicated batches, and second, the shared buffer uncommitted data, and third, the overlapping L0 data, and last, the non-L0 non-overlapping concat-able. These sources used to be passed in as Box<dyn HummockIterator>. Now if we want the MergeIterator to be statically typed, the input type of MergeIterator will become the HummockIteratorUnion of these 4 sources.

Variants

First(I1)

Second(I2)

Third(I3)

Fourth(I4)

Trait Implementations

impl<D: HummockIteratorDirection, I1: HummockIterator<Direction = D>, I2: HummockIterator<Direction = D>, I3: HummockIterator<Direction = D>, I4: HummockIterator<Direction = D>> HummockIterator for HummockIteratorUnion<D, I1, I2, I3, I4>

type Direction = D

async fn next(&mut self) -> HummockResult<()>

Moves a valid iterator to the next key.

fn key(&self) -> FullKey<&[u8]>

Retrieves the current key.

fn value(&self) -> HummockValue<&[u8]>

Retrieves the current value, decoded as HummockValue.

fn is_valid(&self) -> bool

Indicates whether the iterator can be used.

async fn rewind(&mut self) -> HummockResult<()>

Resets the position of the iterator.

async fn seek<'a>(&'a mut self, key: FullKey<&'a [u8]>) -> HummockResult<()>

Resets iterator and seeks to the first position where the key >= provided key, or key <= provided key if this is a backward iterator.

fn collect_local_statistic(&self, stats: &mut StoreLocalStatistic)

take local statistic info from iterator to report metrics.

fn value_meta(&self) -> ValueMeta

Returns value meta.