Enum mz_sql::plan::expr::CoercibleScalarExpr

pub enum CoercibleScalarExpr {
    Coerced(HirScalarExpr),
    Parameter(usize),
    LiteralNull,
    LiteralString(String),
    LiteralRecord(Vec<CoercibleScalarExpr>),
}

A CoercibleScalarExpr is a HirScalarExpr whose type is not fully determined. Several SQL expressions can be freely coerced based upon where in the expression tree they appear. For example, the string literal ‘42’ will be automatically coerced to the integer 42 if used in a numeric context:

SELECT '42' + 42

This separate type gives the code that needs to interact with coercions very fine-grained control over what coercions happen and when.

The primary driver of coercion is function and operator selection, as choosing the correct function or operator implementation depends on the type of the provided arguments. Coercion also occurs at the very root of the scalar expression tree. For example in

SELECT ... WHERE $1

the WHERE clause will coerce the contained unconstrained type parameter $1 to have type bool.

Variants

Coerced(HirScalarExpr)

Parameter(usize)

LiteralNull

LiteralString(String)

LiteralRecord(Vec<CoercibleScalarExpr>)

Implementations

impl CoercibleScalarExpr

pub fn type_as( self, ecx: &ExprContext<'_>, ty: &ScalarType, ) -> Result<HirScalarExpr, PlanError>

pub fn type_as_any( self, ecx: &ExprContext<'_>, ) -> Result<HirScalarExpr, PlanError>

pub fn cast_to( self, ecx: &ExprContext<'_>, ccx: CastContext, ty: &ScalarType, ) -> Result<HirScalarExpr, PlanError>

Trait Implementations

impl AbstractExpr for CoercibleScalarExpr

type Type = CoercibleColumnType

fn typ( &self, outers: &[RelationType], inner: &RelationType, params: &BTreeMap<usize, ScalarType>, ) -> Self::Type

Computes the type of the expression.

impl Clone for CoercibleScalarExpr

fn clone(&self) -> CoercibleScalarExpr

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for CoercibleScalarExpr

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

Formats the value using the given formatter.

impl From<HirScalarExpr> for CoercibleScalarExpr

fn from(expr: HirScalarExpr) -> CoercibleScalarExpr

Converts to this type from the input type.