alamb commented on code in PR #10321:
URL: https://github.com/apache/datafusion/pull/10321#discussion_r1586856895
##########
datafusion/functions/src/core/mod.rs:
##########
@@ -39,14 +42,68 @@ make_udf_function!(getfield::GetFieldFunc, GET_FIELD,
get_field);
make_udf_function!(coalesce::CoalesceFunc, COALESCE, coalesce);
// Export the functions out of this package, both as expr_fn as well as a list
of functions
-export_functions!(
- (nullif, arg_1 arg_2, "returns NULL if value1 equals value2; otherwise it
returns value1. This can be used to perform the inverse operation of the
COALESCE expression."),
- (arrow_cast, arg_1 arg_2, "returns arg_1 cast to the `arrow_type` given
the second argument. This can be used to cast to a specific `arrow_type`."),
- (nvl, arg_1 arg_2, "returns value2 if value1 is NULL; otherwise it returns
value1"),
- (nvl2, arg_1 arg_2 arg_3, "Returns value2 if value1 is not NULL;
otherwise, it returns value3."),
- (arrow_typeof, arg_1, "Returns the Arrow type of the input expression."),
- (r#struct, args, "Returns a struct with the given arguments"),
- (named_struct, args, "Returns a struct with the given names and arguments
pairs"),
- (get_field, arg_1 arg_2, "Returns the value of the field with the given
name from the struct"),
- (coalesce, args, "Returns `coalesce(args...)`, which evaluates to the
value of the first expr which is not NULL")
-);
+pub mod expr_fn {
Review Comment:
What I could't figure out how to do was make the macro take both syntaxes
It would have to look something like
```rust
export_functions!(
// create a function with arg_1 and arg_2 Expr arguments
(arrow_cast, arg_1 arg_2, "returns arg_1 cast to the `arrow_type` given
the second argument. This can be used to cast to a specific `arrow_type`."),
/// create a function with a single Vec<Expr> arg
(coalesce, args, "Returns `coalesce(args...)`, which evaluates to the
value of the first expr which is not NULL")
...
}
```
the macro definition is
https://github.com/apache/datafusion/blob/7c1c7941a078153173a6c82bf2c8742bbcbdefa8/datafusion/functions/src/macros.rs#L39-L60
there may be some way to do this in rust, but I could't figure it out
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