Remove outdated rewrite_expr.rs example (#11085)

* Remove outdated rewrite_expr.rs example

* Update docs

datafusion-examples/README.md

@@ -72,7 +72,6 @@ cargo run --example dataframe
 - [`query-aws-s3.rs`](examples/external_dependency/query-aws-s3.rs): Configure `object_store` and run a query against files stored in AWS S3
 - [`query-http-csv.rs`](examples/query-http-csv.rs): Configure `object_store` and run a query against files vi HTTP
 - [`regexp.rs`](examples/regexp.rs): Examples of using regular expression functions
-- [`rewrite_expr.rs`](examples/rewrite_expr.rs): Define and invoke a custom Query Optimizer pass
 - [`simple_udaf.rs`](examples/simple_udaf.rs): Define and invoke a User Defined Aggregate Function (UDAF)
 - [`simple_udf.rs`](examples/simple_udf.rs): Define and invoke a User Defined Scalar Function (UDF)
 - [`simple_udfw.rs`](examples/simple_udwf.rs): Define and invoke a User Defined Window Function (UDWF)

datafusion/optimizer/README.md

@@ -67,8 +67,10 @@ let optimizer = Optimizer::with_rules(vec![
 
 ## Writing Optimization Rules
 
-Please refer to the [rewrite_expr example](../../datafusion-examples/examples/rewrite_expr.rs) to learn more about
-the general approach to writing optimizer rules and then move onto studying the existing rules.
+Please refer to the
+[optimizer_rule.rs](../../datafusion-examples/examples/optimizer_rule.rs)
+example to learn more about the general approach to writing optimizer rules and
+then move onto studying the existing rules.
 
 All rules must implement the `OptimizerRule` trait.
 

docs/source/library-user-guide/working-with-exprs.md

@@ -80,7 +80,11 @@ If you'd like to learn more about `Expr`s, before we get into the details of cre
 
 ## Rewriting `Expr`s
 
-[rewrite_expr.rs](https://github.com/apache/datafusion/blob/main/datafusion-examples/examples/rewrite_expr.rs) contains example code for rewriting `Expr`s.
+There are several examples of rewriting and working with `Exprs`:
+
+- [expr_api.rs](https://github.com/apache/datafusion/blob/main/datafusion-examples/examples/expr_api.rs)
+- [analyzer_rule.rs](https://github.com/apache/datafusion/blob/main/datafusion-examples/examples/analyzer_rule.rs)
+- [optimizer_rule.rs](https://github.com/apache/datafusion/blob/main/datafusion-examples/examples/optimizer_rule.rs)
 
 Rewriting Expressions is the process of taking an `Expr` and transforming it into another `Expr`. This is useful for a number of reasons, including: