Macros for user-defined window functions

Is your feature request related to a problem or challenge?

Add macros for creating WindowUDF and WindowFunction expression from user-defined window functions.

This will be similar to existing macros in function aggeregates:

datafusion/datafusion/functions-aggregate/src/macros.rs

Lines 54 to 58 in 80848f2

    
           macro_rules! make_udaf_expr_and_func { 
        
               ($UDAF:ty, $EXPR_FN:ident, $($arg:ident)*, $DOC:expr, $AGGREGATE_UDF_FN:ident) => { 
        
                   make_udaf_expr!($EXPR_FN, $($arg)*, $DOC, $AGGREGATE_UDF_FN); 
        
                   create_func!($UDAF, $AGGREGATE_UDF_FN); 
        
               };

Describe the solution you'd like

Existing code which will be replaced by macros:

datafusion/datafusion/functions-window/src/row_number.rs

Lines 35 to 54 in e1b992a

    
           /// Create a [`WindowFunction`](Expr::WindowFunction) expression for 
        
           /// `row_number` user-defined window function. 
        
           pub fn row_number() -> Expr { 
        
               Expr::WindowFunction(WindowFunction::new(row_number_udwf(), vec![])) 
        
           } 
        
           /// Singleton instance of `row_number`, ensures the UDWF is only created once. 
        
           #[allow(non_upper_case_globals)] 
        
           static STATIC_RowNumber: std::sync::OnceLock<std::sync::Arc<datafusion_expr::WindowUDF>> = 
        
               std::sync::OnceLock::new(); 
        
           /// Returns a [`WindowUDF`](datafusion_expr::WindowUDF) for `row_number` 
        
           /// user-defined window function. 
        
           pub fn row_number_udwf() -> std::sync::Arc<datafusion_expr::WindowUDF> { 
        
               STATIC_RowNumber 
        
                   .get_or_init(|| { 
        
                       std::sync::Arc::new(datafusion_expr::WindowUDF::from(RowNumber::default())) 
        
                   }) 
        
                   .clone() 
        
           }

New code using a macro:

define_udwf_and_expr!(
    RowNumber,
    row_number,
    "Returns a unique row number for each row in window partition beginning at 1."
);

The above example combines creating both user-defined window function and expression function API. This should work for majority of the cases.

But separate macros will also be provided for cases where they are necessary.

Describe alternatives you've considered

As we begin to convert remaining BuiltinWindowFunction::* to user-defined window functions this will save developer effort.

Additional context

Part of #8709.
Follow-on to PR #12030.

Needed for #12649, #12648.

@SteNicholas

@SteNicholas Sorry for the confusion. This was unassigned but I already have a PR in the works (#12693).

Here a few more good first issues for user-defined window functions to get you started 😄.

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Macros for user-defined window functions #12688

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	macro_rules! make_udaf_expr_and_func {
	($UDAF:ty, $EXPR_FN:ident, $($arg:ident)*, $DOC:expr, $AGGREGATE_UDF_FN:ident) => {
	make_udaf_expr!($EXPR_FN, $($arg)*, $DOC, $AGGREGATE_UDF_FN);
	create_func!($UDAF, $AGGREGATE_UDF_FN);
	};

	/// Create a [`WindowFunction`](Expr::WindowFunction) expression for
	/// `row_number` user-defined window function.
	pub fn row_number() -> Expr {
	Expr::WindowFunction(WindowFunction::new(row_number_udwf(), vec![]))
	}

	/// Singleton instance of `row_number`, ensures the UDWF is only created once.
	#[allow(non_upper_case_globals)]
	static STATIC_RowNumber: std::sync::OnceLock<std::sync::Arc<datafusion_expr::WindowUDF>> =
	std::sync::OnceLock::new();

	/// Returns a [`WindowUDF`](datafusion_expr::WindowUDF) for `row_number`
	/// user-defined window function.
	pub fn row_number_udwf() -> std::sync::Arc<datafusion_expr::WindowUDF> {
	STATIC_RowNumber
	.get_or_init(\|\| {
	std::sync::Arc::new(datafusion_expr::WindowUDF::from(RowNumber::default()))
	})
	.clone()
	}

Macros for user-defined window functions #12688

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jcsherin commented on Oct 1, 2024

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