Struct Bitmap 

pub struct Bitmap { /* private fields */ }

One bit per value, set meaning valid.

Words are u64 because that is the width the popcount and the mask tests want, and because a 1024 value vector is exactly 16 of them, which fits in a quarter of a cache line pair and is the reason the vector size is 1024 rather than DuckDB’s 2048.

Implementations

impl Bitmap

pub fn footprint(&self) -> usize

How many bytes of memory this bitmap is holding.

pub fn all_valid(len: usize) -> Self

A bitmap with room for len values, all valid.

pub fn all_invalid(len: usize) -> Self

A bitmap with room for len values, all null.

pub fn get(&self, index: usize) -> bool

Whether the value at index is valid. Past the end reads as invalid.

pub fn set(&mut self, index: usize, valid: bool)

Sets whether the value at index is valid, growing the bitmap if it has to.

pub fn count_valid(&self, len: usize) -> usize

How many of the first len values are valid.

pub fn word(&self, at: usize) -> u64

Sixty four validity bits at once, the lowest numbered row in the lowest bit.

Past the end reads as all null, which is the same answer Self::get gives one bit at a time. This exists because a kernel that asks Self::get once per row pays a bounds check, a divide and a shift for each of them, and the word it wants was already in a register for the previous sixty three. A loop that reads the word once and walks its bits is the same answer at a fraction of the cost, and the three call sites that do that are the difference between a nullable column being free and being the slowest thing in the kernel.

pub fn and_with(&mut self, other: &Self)

Intersects this bitmap with another, in place.

Trait Implementations

impl Clone for Bitmap

fn clone(&self) -> Bitmap

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Bitmap

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

Formats the value using the given formatter.

impl Eq for Bitmap

impl PartialEq for Bitmap

fn eq(&self, other: &Bitmap) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Bitmap