Struct sql::plan::expr::ColumnRef

pub struct ColumnRef {
    pub level: usize,
    pub column: usize,
}

A leveled column reference.

In the course of decorrelation, multiple levels of nested subqueries are traversed, and references to columns may correspond to different levels of containing outer subqueries.

A ColumnRef allows expressions to refer to columns while being clear about which level the column references without manually performing the bookkeeping tracking their actual column locations.

Specifically, a ColumnRef refers to a column level subquery level out from the reference, using column as a unique identifier in that subquery level. A level of zero corresponds to the current scope, and levels increase to indicate subqueries further “outwards”.

Fields

level: usize

column: usize

Trait Implementations

impl Clone for ColumnRef

fn clone(&self) -> ColumnRef

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for ColumnRef

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

Formats the value using the given formatter.

impl Hash for ColumnRef

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, 

Feeds a slice of this type into the given Hasher.

impl Ord for ColumnRef

fn cmp(&self, other: &ColumnRef) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl PartialEq<ColumnRef> for ColumnRef

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

This method tests for self and other values to be equal, and is used by ==.

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

This method tests for !=.

impl PartialOrd<ColumnRef> for ColumnRef

fn partial_cmp(&self, other: &ColumnRef) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

This method tests less than (for self and other) and is used by the < operator.

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

This method tests less than or equal to (for self and other) and is used by the <= operator.

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

This method tests greater than (for self and other) and is used by the > operator.

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

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for ColumnRef

impl Eq for ColumnRef

impl StructuralEq for ColumnRef

impl StructuralPartialEq for ColumnRef