NamedArgumentExpression¶

Overview¶

NamedArgumentExpression is a Catalyst expression that represents a named argument in routine calls, allowing arguments to be passed by name rather than position. This expression is used internally to support named parameter syntax in SQL functions, where arguments can be specified with explicit parameter names for better readability and flexibility.

Syntax¶

function_name(parameter_name => value, ...)

Arguments¶

Argument	Type	Description
key	String	The name of the routine argument/parameter
value	Expression	The value expression for the routine argument

Return Type¶

The return type matches the data type of the value expression. Since this is a wrapper expression, it inherits the data type from its child value expression.

Supported Data Types¶

All data types are supported since NamedArgumentExpression acts as a wrapper around any underlying expression. The supported data types depend entirely on the wrapped value expression.

Algorithm¶

Acts as a unary expression wrapper around the value expression
Preserves the data type of the underlying value expression
Provides named parameter semantics for routine calls
Delegates all evaluation logic to the child value expression
Maintains the parameter name for proper argument binding during function resolution

Partitioning Behavior¶

Preserves partitioning: Yes, since it's a wrapper expression that doesn't modify data distribution
Requires shuffle: No, this expression doesn't trigger data shuffling as it only provides naming semantics

Edge Cases¶

Null handling: Inherits null handling behavior from the wrapped value expression
Empty input: Behavior depends on the underlying value expression
Unevaluable: This expression extends Unevaluable, meaning it cannot be directly evaluated and must be processed/transformed during analysis phase
Resolution dependency: The value expression is resolved recursively by Analyzer rules (e.g., ResolveFunctions for built-in functions)

Code Generation¶

This expression does not support code generation as it extends Unevaluable. It serves as an intermediate representation during query analysis and is typically transformed or resolved before the code generation phase.

Examples¶

-- Named arguments in encode function
SELECT encode(charset => "utf-8", value => "abc");

-- Named arguments with mixed positional and named parameters
SELECT some_function(arg1 => 'value1', arg2 => 42);

// This expression is primarily used internally during SQL parsing
// and is not typically created directly in DataFrame API
val namedArg = NamedArgumentExpression("charset", Literal("utf-8"))