alamb commented on a change in pull request #1375:
URL: https://github.com/apache/arrow-datafusion/pull/1375#discussion_r759205639
##########
File path: datafusion/src/optimizer/simplify_expressions.rs
##########
@@ -284,9 +274,62 @@ impl OptimizerRule for SimplifyExpressions {
fn optimize(
&self,
plan: &LogicalPlan,
- _execution_props: &ExecutionProps,
+ execution_props: &ExecutionProps,
) -> Result<LogicalPlan> {
- optimize(plan)
+ // We need to pass down the all schemas within the plan tree to
`optimize_expr` in order to
+ // to evaluate expression types. For example, a projection plan's
schema will only include
+ // projected columns. With just the projected schema, it's not
possible to infer types for
+ // expressions that references non-projected columns within the same
project plan or its
+ // children plans.
+ let mut simplifier =
+ super::simplify_expressions::Simplifier::new(plan.all_schemas());
+
+ let mut const_evaluator =
+ super::simplify_expressions::ConstEvaluator::new(execution_props);
+
+ let new_inputs = plan
+ .inputs()
+ .iter()
+ .map(|input| self.optimize(input, execution_props))
+ .collect::<Result<Vec<_>>>()?;
+
+ let expr = plan
+ .expressions()
+ .into_iter()
+ .map(|e| {
+ // We need to keep original expression name, if any.
+ // Constant folding should not change expression name.
+ let name = &e.name(plan.schema());
+
+ // TODO combine simplify into Simplifier
+ let e = simplify(&e);
+
+ // TODO iterate until no changes are made
+ // during rewrite (evaluating constants can
+ // enable new simplifications and
+ // simplifications can enable new constant
+ // evaluation)
+ let new_e = e
+ // fold constants and then simplify
+ .rewrite(&mut const_evaluator)?
+ .rewrite(&mut simplifier)?;
+
+ let new_name = &new_e.name(plan.schema());
+
+ // TODO simplify this logic
+ if let (Ok(expr_name), Ok(new_expr_name)) = (name, new_name) {
Review comment:
Note that now the fix for alias names (introduced by @viirya in
https://github.com/apache/arrow-datafusion/pull/1319) is applied to the result
of `simplify` as well -- previously it was not 🎉
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