Struct StringView 

pub struct StringView { /* private fields */ }

A 16 byte handle on a string.

The layout is a u32 length and 12 bytes of payload. For a string of 12 bytes or fewer the payload is the string, zero padded. For a longer one the first 4 bytes are the prefix, the next 4 are the index of the block holding it, and the last 4 are the offset into that block.

A view on its own cannot produce a long string, only a short one. That is deliberate: the blocks live in the StringColumn and the borrow checker is what stops a view from outliving them, rather than a rule somebody has to remember.

Implementations

impl StringView

pub fn inline(text: &str) -> Self

A view on a string that fits inline.

Panics

If the string is longer than INLINE_LIMIT. Callers that do not know the length go through StringColumn::push, which decides.

pub fn len(&self) -> usize

The length in bytes.

pub fn is_empty(&self) -> bool

Whether the string is empty.

pub fn is_inline(&self) -> bool

Whether the whole string is in the view.

pub fn prefix(&self) -> [u8; 4]

The first four bytes, zero padded.

This is the whole point of the representation. Two strings with different prefixes are different, and two strings with the same prefix are usually equal, so a filter on a string column resolves without touching the payload on almost every row.

pub fn as_inline_str(&self) -> Option<&str>

The string, when it is short enough to be in the view.

pub fn definitely_differs(&self, other: &Self) -> bool

Whether these two views are definitely different, answered from the view alone.

A false here means the payloads have to be compared. A true means they do not, which on a filter against a selective literal is almost every row.

Trait Implementations

impl Clone for StringView

fn clone(&self) -> StringView

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for StringView

impl Debug for StringView

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

Formats the value using the given formatter.

impl Eq for StringView

impl Hash for StringView

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for StringView

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for StringView