Module tidb_query_expr::types::function

People implementing RPN functions with fixed argument type and count don’t necessarily need to understand how Evaluator and RpnDef work. There’s a procedural macro called rpn_fn defined in tidb_query_codegen to help you create RPN functions. For example:

use tidb_query_codegen::rpn_fn;

#[rpn_fn(nullable)]
fn foo(lhs: &Option<Int>, rhs: &Option<Int>) -> Result<Option<Int>> {
    // Your RPN function logic
}

You can still call the foo function directly; the macro preserves the original function It creates a foo_fn_meta() function (simply add _fn_meta to the original function name) which generates an RpnFnMeta struct.

For more information on the procedural macro, see the documentation in components/tidb_query_codegen/src/rpn_function.

Structs

Arg	RPN function argument definitions in the form of a linked list.
ArgConstructor
Null	Represents the end of the argument list.
RpnFnCallExtra	Extra information about an RPN function call.
RpnFnMeta	Metadata of an RPN function.
ScalarArg	Represents an RPN function argument of a ScalarValue.
VectorArg	Represents an RPN function argument of a VectorValue.

Constants

RAW_VARG_PARAM_BUF
VARG_PARAM_BUF
VARG_PARAM_BUF_BYTES_REF
VARG_PARAM_BUF_JSON_REF

Traits

ArgDef	Partial or complete argument definition of an RPN function.
Evaluator	A generic evaluator of an RPN function.
RpnFnArg	A single argument of an RPN function.

Functions

extract_metadata_from_val
validate_expr_arguments_eq	Validates whether the number of arguments of an expression node meets expectation.
validate_expr_arguments_gte	Validates whether the number of arguments of an expression node >= expectation.
validate_expr_arguments_lte	Validates whether the number of arguments of an expression node <= expectation.
validate_expr_return_type	Validates whether the return type of an expression node meets expectation.