datafusion_functions_nested/
macros.rs

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8//
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16// under the License.
17
18/// Creates external API functions for an array UDF. Specifically, creates
19///
20/// 1. Single `ScalarUDF` instance
21///
22/// Creates a singleton `ScalarUDF` of the `$UDF` function named `STATIC_$(UDF)` and a
23/// function named `$SCALAR_UDF_FUNC` which returns that function named `STATIC_$(UDF)`.
24///
25/// This is used to ensure creating the list of `ScalarUDF` only happens once.
26///
27/// # 2. `expr_fn` style function
28///
29/// These are functions that create an `Expr` that invokes the UDF, used
30/// primarily to programmatically create expressions.
31///
32/// For example:
33/// ```text
34/// pub fn array_to_string(delimiter: Expr) -> Expr {
35/// ...
36/// }
37/// ```
38/// # Arguments
39/// * `UDF`: name of the [`ScalarUDFImpl`]
40/// * `EXPR_FN`: name of the expr_fn function to be created
41/// * `arg`: 0 or more named arguments for the function
42/// * `DOC`: documentation string for the function
43/// * `SCALAR_UDF_FUNC`: name of the function to create (just) the `ScalarUDF`
44/// * (optional) `$CTOR`: Pass a custom constructor. When omitted it
45///   automatically resolves to `$UDF::new()`.
46///
47/// [`ScalarUDFImpl`]: datafusion_expr::ScalarUDFImpl
48macro_rules! make_udf_expr_and_func {
49    ($UDF:ident, $EXPR_FN:ident, $($arg:ident)*, $DOC:expr, $SCALAR_UDF_FN:ident) => {
50        make_udf_expr_and_func!($UDF, $EXPR_FN, $($arg)*, $DOC, $SCALAR_UDF_FN, $UDF::new);
51    };
52    ($UDF:ident, $EXPR_FN:ident, $($arg:ident)*, $DOC:expr, $SCALAR_UDF_FN:ident, $CTOR:path) => {
53            // "fluent expr_fn" style function
54            #[doc = $DOC]
55            pub fn $EXPR_FN($($arg: datafusion_expr::Expr),*) -> datafusion_expr::Expr {
56                datafusion_expr::Expr::ScalarFunction(datafusion_expr::expr::ScalarFunction::new_udf(
57                    $SCALAR_UDF_FN(),
58                    vec![$($arg),*],
59                ))
60            }
61            create_func!($UDF, $SCALAR_UDF_FN, $CTOR);
62    };
63    ($UDF:ident, $EXPR_FN:ident, $DOC:expr, $SCALAR_UDF_FN:ident) => {
64        make_udf_expr_and_func!($UDF, $EXPR_FN, $DOC, $SCALAR_UDF_FN, $UDF::new);
65    };
66    ($UDF:ident, $EXPR_FN:ident, $DOC:expr, $SCALAR_UDF_FN:ident, $CTOR:path) => {
67            // "fluent expr_fn" style function
68            #[doc = $DOC]
69            pub fn $EXPR_FN(arg: Vec<datafusion_expr::Expr>) -> datafusion_expr::Expr {
70                datafusion_expr::Expr::ScalarFunction(datafusion_expr::expr::ScalarFunction::new_udf(
71                    $SCALAR_UDF_FN(),
72                    arg,
73                ))
74            }
75            create_func!($UDF, $SCALAR_UDF_FN, $CTOR);
76    };
77}
78
79/// Creates a singleton `ScalarUDF` of the `$UDF` function named `STATIC_$(UDF)` and a
80/// function named `$SCALAR_UDF_FUNC` which returns that function named `STATIC_$(UDF)`.
81///
82/// This is used to ensure creating the list of `ScalarUDF` only happens once.
83///
84/// # Arguments
85/// * `UDF`: name of the [`ScalarUDFImpl`]
86/// * `SCALAR_UDF_FUNC`: name of the function to create (just) the `ScalarUDF`
87/// * (optional) `$CTOR`: Pass a custom constructor. When omitted it
88///   automatically resolves to `$UDF::new()`.
89///
90/// [`ScalarUDFImpl`]: datafusion_expr::ScalarUDFImpl
91macro_rules! create_func {
92    ($UDF:ident, $SCALAR_UDF_FN:ident) => {
93        create_func!($UDF, $SCALAR_UDF_FN, $UDF::new);
94    };
95    ($UDF:ident, $SCALAR_UDF_FN:ident, $CTOR:path) => {
96            #[doc = concat!("ScalarFunction that returns a [`ScalarUDF`](datafusion_expr::ScalarUDF) for ")]
97            #[doc = stringify!($UDF)]
98            pub fn $SCALAR_UDF_FN() -> std::sync::Arc<datafusion_expr::ScalarUDF> {
99                // Singleton instance of [`$UDF`], ensures the UDF is only created once
100                static INSTANCE: std::sync::LazyLock<std::sync::Arc<datafusion_expr::ScalarUDF>> =
101                    std::sync::LazyLock::new(|| {
102                        std::sync::Arc::new(datafusion_expr::ScalarUDF::new_from_impl(
103                            $CTOR(),
104                        ))
105                    });
106                std::sync::Arc::clone(&INSTANCE)
107            }
108    };
109}
datafusion_functions_nested/macros.rs

datafusion_functions_nested/
macros.rs
