[GitHub] [arrow-datafusion] HaoYang670 commented on a change in pull request #1734: Create built-in scalar functions programmatically

[GitBox <gi...@apache.org>]

HaoYang670 commented on a change in pull request #1734:
URL: https://github.com/apache/arrow-datafusion/pull/1734#discussion_r800000256



##########
File path: datafusion/src/logical_plan/expr.rs
##########
@@ -2189,6 +2189,20 @@ pub fn exprlist_to_fields<'a>(
     expr.into_iter().map(|e| e.to_field(input_schema)).collect()
 }
 
+/// Calls a named built in function
+/// ```
+/// use datafusion::logical_plan::*;
+///
+/// // create the expression sin(x) < 0.2
+/// let expr = call_builtin_scalar_fn("sin", vec![col("x")]).unwrap().lt(lit(0.2));
+/// ```
+pub fn call_builtin_scalar_fn(name: impl AsRef<str>, args: Vec<Expr>) -> Result<Expr> {
+    match name.as_ref().parse::<functions::BuiltinScalarFunction>() {
+        Ok(fun) => Ok(Expr::ScalarFunction { fun, args }),
+        Err(e) => Err(e),
+    }

Review comment:
       Agree with you @Jimexist ! 
   
   And alamb 's opinion of the trade-off between macro and function call is here: 
   https://github.com/apache/arrow-datafusion/issues/1718#issuecomment-1026239024




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