Support aliases in ConstEvaluator (apache#14734)

Not sure why they are not supported. It seems that if we're not careful,
some transformations can introduce aliases nested inside other expressions.

Author: joroKr21

datafusion/core/tests/expr_api/simplification.rs

@@ -365,6 +365,33 @@ fn test_const_evaluator() {
     );
 }
 
+#[test]
+fn test_const_evaluator_alias() {
+    // true --> true
+    test_evaluate(lit(true).alias("a"), lit(true));
+    // true or true --> true
+    test_evaluate(lit(true).alias("a").or(lit(true).alias("b")), lit(true));
+    // "foo" == "foo" --> true
+    test_evaluate(lit("foo").alias("a").eq(lit("foo").alias("b")), lit(true));
+    // c = 1 + 2 --> c + 3
+    test_evaluate(
+        col("c")
+            .alias("a")
+            .eq(lit(1).alias("b") + lit(2).alias("c")),
+        col("c").alias("a").eq(lit(3)),
+    );
+    // (foo != foo) OR (c = 1) --> false OR (c = 1)
+    test_evaluate(
+        lit("foo")
+            .alias("a")
+            .not_eq(lit("foo").alias("b"))
+            .alias("c")
+            .or(col("c").alias("d").eq(lit(1).alias("e")))
+            .alias("f"),
+        col("c").alias("d").eq(lit(1)).alias("f"),
+    );
+}
+
 #[test]
 fn test_const_evaluator_scalar_functions() {
     // concat("foo", "bar") --> "foobar"

datafusion/optimizer/src/simplify_expressions/expr_simplifier.rs

@@ -45,14 +45,13 @@ use datafusion_expr::{
 use datafusion_physical_expr::{create_physical_expr, execution_props::ExecutionProps};
 use indexmap::IndexSet;
 
+use super::inlist_simplifier::ShortenInListSimplifier;
+use super::utils::*;
 use crate::analyzer::type_coercion::TypeCoercionRewriter;
 use crate::simplify_expressions::guarantees::GuaranteeRewriter;
 use crate::simplify_expressions::regex::simplify_regex_expr;
 use crate::simplify_expressions::SimplifyInfo;
 
-use super::inlist_simplifier::ShortenInListSimplifier;
-use super::utils::*;
-
 /// This structure handles API for expression simplification
 ///
 /// Provides simplification information based on DFSchema and
@@ -514,30 +513,27 @@ impl<'a> TreeNodeRewriter for ConstEvaluator<'a> {
 
         // NB: do not short circuit recursion even if we find a non
         // evaluatable node (so we can fold other children, args to
-        // functions, etc)
+        // functions, etc.)
         Ok(Transformed::no(expr))
     }
 
     fn f_up(&mut self, expr: Expr) -> Result<Transformed<Expr>> {
         match self.can_evaluate.pop() {
-            // Certain expressions such as `CASE` and `COALESCE` are short circuiting
-            // and may not evaluate all their sub expressions. Thus if
-            // if any error is countered during simplification, return the original
+            // Certain expressions such as `CASE` and `COALESCE` are short-circuiting
+            // and may not evaluate all their sub expressions. Thus, if
+            // any error is countered during simplification, return the original
             // so that normal evaluation can occur
-            Some(true) => {
-                let result = self.evaluate_to_scalar(expr);
-                match result {
-                    ConstSimplifyResult::Simplified(s) => {
-                        Ok(Transformed::yes(Expr::Literal(s)))
-                    }
-                    ConstSimplifyResult::NotSimplified(s) => {
-                        Ok(Transformed::no(Expr::Literal(s)))
-                    }
-                    ConstSimplifyResult::SimplifyRuntimeError(_, expr) => {
-                        Ok(Transformed::yes(expr))
-                    }
+            Some(true) => match self.evaluate_to_scalar(expr) {
+                ConstSimplifyResult::Simplified(s) => {
+                    Ok(Transformed::yes(Expr::Literal(s)))
                 }
-            }
+                ConstSimplifyResult::NotSimplified(s) => {
+                    Ok(Transformed::no(Expr::Literal(s)))
+                }
+                ConstSimplifyResult::SimplifyRuntimeError(_, expr) => {
+                    Ok(Transformed::yes(expr))
+                }
+            },
             Some(false) => Ok(Transformed::no(expr)),
             _ => internal_err!("Failed to pop can_evaluate"),
         }
@@ -585,9 +581,7 @@ impl<'a> ConstEvaluator<'a> {
         // added they can be checked for their ability to be evaluated
         // at plan time
         match expr {
-            // Has no runtime cost, but needed during planning
-            Expr::Alias(..)
-            | Expr::AggregateFunction { .. }
+            Expr::AggregateFunction { .. }
             | Expr::ScalarVariable(_, _)
             | Expr::Column(_)
             | Expr::OuterReferenceColumn(_, _)
@@ -602,6 +596,7 @@ impl<'a> ConstEvaluator<'a> {
                 Self::volatility_ok(func.signature().volatility)
             }
             Expr::Literal(_)
+            | Expr::Alias(..)
             | Expr::Unnest(_)
             | Expr::BinaryExpr { .. }
             | Expr::Not(_)

datafusion/sqllogictest/test_files/subquery.slt

@@ -830,7 +830,7 @@ query TT
 explain SELECT t1_id, (SELECT count(*) as _cnt FROM t2 WHERE t2.t2_int = t1.t1_int) as cnt from t1
 ----
 logical_plan
-01)Projection: t1.t1_id, CASE WHEN __scalar_sq_1.__always_true IS NULL THEN Int64(0) AS _cnt ELSE __scalar_sq_1._cnt END AS cnt
+01)Projection: t1.t1_id, CASE WHEN __scalar_sq_1.__always_true IS NULL THEN Int64(0) ELSE __scalar_sq_1._cnt END AS cnt
 02)--Left Join: t1.t1_int = __scalar_sq_1.t2_int
 03)----TableScan: t1 projection=[t1_id, t1_int]
 04)----SubqueryAlias: __scalar_sq_1
@@ -851,7 +851,7 @@ query TT
 explain SELECT t1_id, (SELECT count(*) + 2 as _cnt FROM t2 WHERE t2.t2_int = t1.t1_int) from t1
 ----
 logical_plan
-01)Projection: t1.t1_id, CASE WHEN __scalar_sq_1.__always_true IS NULL THEN Int64(2) AS _cnt ELSE __scalar_sq_1._cnt END AS _cnt
+01)Projection: t1.t1_id, CASE WHEN __scalar_sq_1.__always_true IS NULL THEN Int64(2) ELSE __scalar_sq_1._cnt END AS _cnt
 02)--Left Join: t1.t1_int = __scalar_sq_1.t2_int
 03)----TableScan: t1 projection=[t1_id, t1_int]
 04)----SubqueryAlias: __scalar_sq_1
@@ -918,7 +918,7 @@ query TT
 explain SELECT t1_id, (SELECT count(*) + 2 as cnt_plus_2 FROM t2 WHERE t2.t2_int = t1.t1_int having count(*) = 0) from t1
 ----
 logical_plan
-01)Projection: t1.t1_id, CASE WHEN __scalar_sq_1.__always_true IS NULL THEN Int64(2) AS cnt_plus_2 WHEN __scalar_sq_1.count(*) != Int64(0) THEN NULL ELSE __scalar_sq_1.cnt_plus_2 END AS cnt_plus_2
+01)Projection: t1.t1_id, CASE WHEN __scalar_sq_1.__always_true IS NULL THEN Int64(2) WHEN __scalar_sq_1.count(*) != Int64(0) THEN NULL ELSE __scalar_sq_1.cnt_plus_2 END AS cnt_plus_2
 02)--Left Join: t1.t1_int = __scalar_sq_1.t2_int
 03)----TableScan: t1 projection=[t1_id, t1_int]
 04)----SubqueryAlias: __scalar_sq_1