[GitHub] [arrow-datafusion] liukun4515 commented on a diff in pull request #3636: move the `type coercion` to the beginning of the optimizer rule and support type coercion for subquery

[GitBox]

liukun4515 commented on code in PR #3636:
URL: https://github.com/apache/arrow-datafusion/pull/3636#discussion_r982957302


##########
datafusion/core/src/execution/context.rs:
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@@ -1466,10 +1466,9 @@ impl SessionState {
         }
 
         let mut rules: Vec<Arc<dyn OptimizerRule + Sync + Send>> = vec![
-            // Simplify expressions first to maximize the chance
-            // of applying other optimizations
-            Arc::new(SimplifyExpressions::new()),
             Arc::new(PreCastLitInComparisonExpressions::new()),

Review Comment:
   The `PreCastLitInComparisonExpressions` will be invalid when we move the 
`type coercion` to the front of `PreCastLitInComparisonExpressions`.
   
   In the next pr, I will do 
https://github.com/apache/arrow-datafusion/issues/3622 and move the type 
coercion to the front of the `PreCastLitInComparisonExpressions`
   
   
   I think `type coercion` just do one thing which is make type compatible in 
all operation, but the `PreCastLitInComparisonExpressions` or 
https://github.com/apache/arrow-datafusion/issues/3622 is to reduce `cast` for 
column expr or other expr instead of adding the `cast` to the literal. This 
will reduce the cast effort of the runtime.



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