Struct sql::plan::typeconv::CastTemplate

struct CastTemplate(Box<dyn Fn(&ExprContext<'_>, CastContext, &ScalarType, &ScalarType) -> Option<Box<dyn FnOnce(HirScalarExpr) -> HirScalarExpr>> + Send + Sync>);

A cast template is a function that produces a Cast given a concrete input and output type. A template can return None to indicate that it is incapable of producing a cast for the specified types.

Cast templates are used to share code for similar casts, where the input or output type is of one “category” of type. For example, a single cast template handles converting from strings to any list type. Without cast templates, we’d have to enumerate every possible list -> list conversion, which is impractical.

Tuple Fields

0: Box<dyn Fn(&ExprContext<'_>, CastContext, &ScalarType, &ScalarType) -> Option<Box<dyn FnOnce(HirScalarExpr) -> HirScalarExpr>> + Send + Sync>

Implementations

impl CastTemplate

fn new<T, C>(t: T) -> CastTemplate where
    T: Fn(&ExprContext<'_>, CastContext, &ScalarType, &ScalarType) -> Option<C> + Send + Sync + 'static,
    C: FnOnce(HirScalarExpr) -> HirScalarExpr + 'static, 

Trait Implementations

impl From<UnaryFunc> for CastTemplate

fn from(u: UnaryFunc) -> CastTemplate

Performs the conversion.