Enum ColumnUsage 

pub enum ColumnUsage {
    Unknown,
    Known(HashSet<String>),
}

Enum storing info on which dataset columns are used in a given context. Due to the dynamic nature of Vega specifications, it’s not always possible to statically determine which columns from a dataset will be used at runtime. In this case the ColumnUsage::Unknown variant is used. In the context of projection pushdown, the ColumnUsage::Unknown variant indicates that all of original dataset columns must be maintained

Variants

Unknown

Known(HashSet<String>)

Implementations

impl ColumnUsage

pub fn empty() -> ColumnUsage

pub fn with_column(&self, column: &str) -> ColumnUsage

pub fn union(&self, other: &ColumnUsage) -> ColumnUsage

Take the union of two ColumnUsage instances. If both are ColumnUsage::Known, then take the union of their known columns. If either is ColumnUsage::Unknown, then the union is also Unknown.

pub fn difference(&self, other: &ColumnUsage) -> ColumnUsage

Trait Implementations

impl Clone for ColumnUsage

fn clone(&self) -> ColumnUsage

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ColumnUsage

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

Formats the value using the given formatter.

impl From<&[&str]> for ColumnUsage

fn from(columns: &[&str]) -> Self

Converts to this type from the input type.

impl From<&[String]> for ColumnUsage

fn from(columns: &[String]) -> Self

Converts to this type from the input type.

impl From<&str> for ColumnUsage

fn from(column: &str) -> Self

Converts to this type from the input type.

impl PartialEq for ColumnUsage

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for ColumnUsage

impl StructuralPartialEq for ColumnUsage