Struct ConstExpr

pub struct ConstExpr {
    pub expr: Arc<dyn PhysicalExpr>,
    pub across_partitions: AcrossPartitions,
}

A structure representing a expression known to be constant in a physical execution plan.

The ConstExpr struct encapsulates an expression that is constant during the execution of a query. For example if a filter like A = 5 appears earlier in the plan, A would become a constant in subsequent operations.

Fields

• expr: Constant expression for a node in the physical plan.
• across_partitions: A boolean flag indicating whether the constant expression is the same across partitions. If set to true, the constant expression has same value for all partitions. If set to false, the constant expression may have different values for different partitions.

Example

let col = lit(5);
// Create a constant expression from a physical expression:
let const_expr = ConstExpr::from(col);

Fields

expr: Arc<dyn PhysicalExpr>

The expression that is known to be constant (e.g. a Column).

across_partitions: AcrossPartitions

Indicates whether the constant have the same value across all partitions.

Implementations

impl ConstExpr

pub fn new( expr: Arc<dyn PhysicalExpr>, across_partitions: AcrossPartitions, ) -> ConstExpr

Create a new constant expression from a physical expression, specifying whether the constant expression is the same across partitions.

Note that you can also use ConstExpr::from to create a constant expression from just a physical expression, with the safe assumption of heterogenous values across partitions unless the expression is a literal.

pub fn format_list(input: &[ConstExpr]) -> impl Display

Returns a Displayable list of ConstExpr.

Trait Implementations

impl Clone for ConstExpr

fn clone(&self) -> ConstExpr

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ConstExpr

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

Formats the value using the given formatter.

impl Display for ConstExpr

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

Formats the value using the given formatter.

impl From<Arc<dyn PhysicalExpr>> for ConstExpr

fn from(expr: Arc<dyn PhysicalExpr>) -> ConstExpr

Converts to this type from the input type.

impl PartialEq for ConstExpr

fn eq(&self, other: &ConstExpr) -> 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.