Struct Rids

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pub struct Rids { /* private fields */ }

Expand description

A set of row ids of one table of a known number of rows.

Implementations§

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impl Rids

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pub fn full(rows: u64) -> Self

Every row of a table of rows.

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pub fn none(rows: u64) -> Self

No row of a table of rows.

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pub fn from_sorted(rows: u64, members: Vec<Rid>) -> Result<Self>

The set holding exactly members, which have to be strictly increasing and below rows.

§Errors

If a member is out of order, repeated or past the end. A set that silently dropped one of those would be a reduction that removed a row which joins.

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pub fn from_words(rows: u64, words: Vec<u64>) -> Result<Self>

The set whose members are the set bits of words, least significant bit of word zero first.

§Errors

If words is not the number of words rows bits take, or a bit past rows is set.

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pub fn rows(&self) -> u64

Rows in the table this is a set over.

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pub fn len(&self) -> u64

Rows in the set.

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pub fn is_empty(&self) -> bool

Whether no row is in the set.

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pub fn is_full(&self) -> bool

Whether every row is in the set.

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pub fn form(&self) -> Form

Which form the set is held in.

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pub fn bytes(&self) -> usize

Bytes the set holds on to.

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pub fn contains(&self, rid: Rid) -> bool

Whether rid is in the set.

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pub fn any_between(&self, low: Rid, high: Rid) -> bool

Whether any member is between low and high, both included.

The question a part skip asks: the link’s zone map says the children of this part point at parents in that range, and a range holding no member is a part that cannot contribute.

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pub fn iter(&self) -> impl Iterator<Item = Rid> + '_

The members, in increasing order.

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pub fn intersect(&self, other: &Self) -> Result<Self>

The rows in both sets.

§Errors

If the two are over tables of different sizes, which is two different tables.

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pub fn union(&self, other: &Self) -> Result<Self>

The rows in either set.

§Errors

If the two are over tables of different sizes.

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pub fn forward(&self, link: &Link) -> Result<Pushed>

Pushes a set of parent rows forward through link, to the child rows that point into it.

One pass over the link in child order, which is section 4.3’s first push. A part whose zone map says its children point only at parents outside the set is never decoded, which is section 5.5’s part skip and on a child clustered by the parent is most of the table.

§Errors

If this set is not over the link’s parent table.

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pub fn forward_or_stop(&self, link: &Link) -> Result<Pushed>

The same push, giving up once it is plain that the set removes nothing.

Section 5.4’s early stop. A push that has covered the first STOP_AFTERth of the child and kept every row of it stops there and hands back every row, so a reduction that was never going to remove anything costs a third of a push and then nothing, where finishing would cost the rest of the push and a bit test per row of the scan. The answer is then a superset of the children that point into the set, which is all a join that still matches every row needs, and Pushed::stopped says so.

§Errors

If this set is not over the link’s parent table.

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pub fn backward(&self, link: &Link) -> Result<Self>

Pushes a set of child rows backward through link, to the parents they point at.

The second push of section 4.3, a pass over the link setting a bit per surviving child. It reads the link in child order just as the forward push does, so it needs no backward structure, and a child without a parent contributes nothing.