Dandandan commented on a change in pull request #8746:
URL: https://github.com/apache/arrow/pull/8746#discussion_r528945232
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File path: rust/datafusion/src/optimizer/utils.rs
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@@ -216,26 +238,51 @@ pub fn from_plan(
/// Returns all direct children `Expression`s of `expr`.
/// E.g. if the expression is "(a + 1) + 1", it returns ["a + 1", "1"] (as
Expr objects)
-pub fn expr_sub_expressions(expr: &Expr) -> Result<Vec<&Expr>> {
+pub fn expr_sub_expressions(expr: &Expr) -> Result<Vec<Expr>> {
match expr {
- Expr::BinaryExpr { left, right, .. } => Ok(vec![left, right]),
- Expr::IsNull(e) => Ok(vec![e]),
- Expr::IsNotNull(e) => Ok(vec![e]),
- Expr::ScalarFunction { args, .. } => Ok(args.iter().collect()),
- Expr::ScalarUDF { args, .. } => Ok(args.iter().collect()),
- Expr::AggregateFunction { args, .. } => Ok(args.iter().collect()),
- Expr::AggregateUDF { args, .. } => Ok(args.iter().collect()),
- Expr::Cast { expr, .. } => Ok(vec![expr]),
+ Expr::BinaryExpr { left, right, .. } => {
+ Ok(vec![left.as_ref().to_owned(), right.as_ref().to_owned()])
+ }
+ Expr::IsNull(e) => Ok(vec![e.as_ref().to_owned()]),
+ Expr::IsNotNull(e) => Ok(vec![e.as_ref().to_owned()]),
+ Expr::ScalarFunction { args, .. } => Ok(args.iter().map(|e|
e.clone()).collect()),
+ Expr::ScalarUDF { args, .. } => Ok(args.iter().map(|e|
e.clone()).collect()),
+ Expr::AggregateFunction { args, .. } => {
+ Ok(args.iter().map(|e| e.clone()).collect())
+ }
+ Expr::AggregateUDF { args, .. } => Ok(args.iter().map(|e|
e.clone()).collect()),
+ Expr::Case {
+ expr,
+ when_then_expr,
+ else_expr,
+ ..
+ } => {
+ let mut expr_list: Vec<Expr> = vec![];
Review comment:
FYI, I started/designed for the Polars library something a bit inspired
by the Spark catalyst optimizer (
http://people.csail.mit.edu/matei/papers/2015/sigmod_spark_sql.pdf ), but a bit
evolved in some ways to be useful in Rust. Specifically, it uses an arena to
mutate the tree efficiently / without cloning.
Code lives here currently:
https://github.com/ritchie46/polars/blob/master/polars/src/lazy/logical_plan/optimizer/simplify_expr.rs#L777
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