[GitHub] [arrow] alamb commented on a change in pull request #9278: ARROW-11330: [Rust][DataFusion] add ExpressionVisitor to encode expression walking

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

alamb commented on a change in pull request #9278:
URL: https://github.com/apache/arrow/pull/9278#discussion_r561197743



##########
File path: rust/datafusion/src/optimizer/utils.rs
##########
@@ -46,75 +50,48 @@ pub fn exprlist_to_column_names(
 
 /// Recursively walk an expression tree, collecting the unique set of column names
 /// referenced in the expression
-pub fn expr_to_column_names(expr: &Expr, accum: &mut HashSet<String>) -> Result<()> {

Review comment:
       This is a pretty good example of the kind of repetition that can be removed using this visitor pattern.
   Note that I still left all expr types enumerated so that anyone who adds a new Expr type need to update this code, and (hopefully) think if they need to add special handling for that new expr types
   




----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

For queries about this service, please contact Infrastructure at:
users@infra.apache.org