andygrove commented on a change in pull request #8746:
URL: https://github.com/apache/arrow/pull/8746#discussion_r529223608
##########
File path: rust/datafusion/src/logical_plan/expr.rs
##########
@@ -342,6 +386,82 @@ impl Expr {
}
}
+pub struct CaseWhenBuilder {
+ expr: Option<Box<Expr>>,
+ when_expr: Vec<Expr>,
+ then_expr: Vec<Expr>,
+}
+
+pub struct CaseThenBuilder {
+ expr: Option<Box<Expr>>,
+ when_expr: Vec<Expr>,
+ then_expr: Vec<Expr>,
+}
+
+impl CaseWhenBuilder {
+ pub fn when(&mut self, expr: Expr) -> CaseThenBuilder {
+ self.when_expr.push(expr);
+ CaseThenBuilder {
+ expr: self.expr.clone(),
+ when_expr: self.when_expr.clone(),
+ then_expr: self.then_expr.clone(),
+ }
+ }
+ pub fn or_else(&mut self, else_expr: Expr) -> Expr {
+ Expr::Case {
+ expr: self.expr.clone(),
+ when_then_expr: self
+ .when_expr
+ .iter()
+ .zip(self.then_expr.iter())
+ .map(|(w, t)| (Box::new(w.clone()), Box::new(t.clone())))
+ .collect(),
+ else_expr: Some(Box::new(else_expr)),
+ }
+ }
+ pub fn end(&mut self) -> Expr {
+ Expr::Case {
+ expr: self.expr.clone(),
+ when_then_expr: self
+ .when_expr
+ .iter()
+ .zip(self.then_expr.iter())
+ .map(|(w, t)| (Box::new(w.clone()), Box::new(t.clone())))
+ .collect(),
+ else_expr: None,
+ }
+ }
+}
Review comment:
I was aiming for a fluent-style API but this could work too. I will take
a look at some other DataFrame APIs tomorrow (pandas, spark, etc) and see how
they do it.
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