Avoid changing expression names during constant folding (#1319)

* Avoid changing output column name before pushdown projection.

* Avoid early optimization which is duplicate.

* Modify test.

* Revert "Modify test."

This reverts commit ebf67d3.

* Revert "Avoid early optimization which is duplicate."

This reverts commit fe8445d.

* Add aliases during constant folding.

* Some expressions don't support name.

* Don't create redundant alias.

* Only add alias for certain plans.

* Fix clippy.

* Fix.

* Revert "Fix."

This reverts commit d767aeb.

* Apply to all nodes and update tests.

* Unalias when push donw to TableScan.

* Update more tests.

* Remove previous change.

datafusion/src/logical_plan/expr.rs

@@ -1349,6 +1349,15 @@ pub fn unnormalize_cols(exprs: impl IntoIterator<Item = Expr>) -> Vec<Expr> {
     exprs.into_iter().map(unnormalize_col).collect()
 }
 
+/// Recursively un-alias an expressions
+#[inline]
+pub fn unalias(expr: Expr) -> Expr {
+    match expr {
+        Expr::Alias(sub_expr, _) => unalias(*sub_expr),
+        _ => expr,
+    }
+}
+
 /// Create an expression to represent the min() aggregate function
 pub fn min(expr: Expr) -> Expr {
     Expr::AggregateFunction {

datafusion/src/logical_plan/mod.rs

@@ -44,7 +44,7 @@ pub use expr::{
     max, md5, min, normalize_col, normalize_cols, now, octet_length, or, random,
     regexp_match, regexp_replace, repeat, replace, replace_col, reverse, right, round,
     rpad, rtrim, sha224, sha256, sha384, sha512, signum, sin, split_part, sqrt,
-    starts_with, strpos, substr, sum, tan, to_hex, translate, trim, trunc,
+    starts_with, strpos, substr, sum, tan, to_hex, translate, trim, trunc, unalias,
     unnormalize_col, unnormalize_cols, upper, when, Column, Expr, ExprRewriter,
     ExpressionVisitor, Literal, Recursion, RewriteRecursion,
 };

datafusion/src/optimizer/constant_folding.rs

@@ -92,6 +92,10 @@ impl OptimizerRule for ConstantFolding {
                     .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 iterate until no changes are made
                         // during rewrite (evaluating constants can
                         // enable new simplifications and
@@ -101,7 +105,18 @@ impl OptimizerRule for ConstantFolding {
                             // fold constants and then simplify
                             .rewrite(&mut const_evaluator)?
                             .rewrite(&mut simplifier)?;
-                        Ok(new_e)
+
+                        let new_name = &new_e.name(plan.schema());
+
+                        if let (Ok(expr_name), Ok(new_expr_name)) = (name, new_name) {
+                            if expr_name != new_expr_name {
+                                Ok(new_e.alias(expr_name))
+                            } else {
+                                Ok(new_e)
+                            }
+                        } else {
+                            Ok(new_e)
+                        }
                     })
                     .collect::<Result<Vec<_>>>()?;
 
@@ -626,8 +641,8 @@ mod tests {
 
         let expected = "\
         Projection: #test.a\
-        \n  Filter: NOT #test.c\
-        \n    Filter: #test.b\
+        \n  Filter: NOT #test.c AS test.c = Boolean(false)\
+        \n    Filter: #test.b AS test.b = Boolean(true)\
         \n      TableScan: test projection=None";
 
         assert_optimized_plan_eq(&plan, expected);
@@ -647,8 +662,8 @@ mod tests {
         let expected = "\
         Projection: #test.a\
         \n  Limit: 1\
-        \n    Filter: #test.c\
-        \n      Filter: NOT #test.b\
+        \n    Filter: #test.c AS test.c != Boolean(false)\
+        \n      Filter: NOT #test.b AS test.b != Boolean(true)\
         \n        TableScan: test projection=None";
 
         assert_optimized_plan_eq(&plan, expected);
@@ -665,7 +680,7 @@ mod tests {
 
         let expected = "\
         Projection: #test.a\
-        \n  Filter: NOT #test.b AND #test.c\
+        \n  Filter: NOT #test.b AND #test.c AS test.b != Boolean(true) AND test.c = Boolean(true)\
         \n    TableScan: test projection=None";
 
         assert_optimized_plan_eq(&plan, expected);
@@ -682,7 +697,7 @@ mod tests {
 
         let expected = "\
         Projection: #test.a\
-        \n  Filter: NOT #test.b OR NOT #test.c\
+        \n  Filter: NOT #test.b OR NOT #test.c AS test.b != Boolean(true) OR test.c = Boolean(false)\
         \n    TableScan: test projection=None";
 
         assert_optimized_plan_eq(&plan, expected);
@@ -699,7 +714,7 @@ mod tests {
 
         let expected = "\
         Projection: #test.a\
-        \n  Filter: #test.b\
+        \n  Filter: #test.b AS NOT test.b = Boolean(false)\
         \n    TableScan: test projection=None";
 
         assert_optimized_plan_eq(&plan, expected);
@@ -714,7 +729,7 @@ mod tests {
             .build()?;
 
         let expected = "\
-        Projection: #test.a, #test.d, NOT #test.b\
+        Projection: #test.a, #test.d, NOT #test.b AS test.b = Boolean(false)\
         \n  TableScan: test projection=None";
 
         assert_optimized_plan_eq(&plan, expected);
@@ -733,7 +748,7 @@ mod tests {
             .build()?;
 
         let expected = "\
-        Aggregate: groupBy=[[#test.a, #test.c]], aggr=[[MAX(#test.b), MIN(#test.b)]]\
+        Aggregate: groupBy=[[#test.a, #test.c]], aggr=[[MAX(#test.b) AS MAX(test.b = Boolean(true)), MIN(#test.b)]]\
         \n  Projection: #test.a, #test.c, #test.b\
         \n    TableScan: test projection=None";
 
@@ -789,7 +804,7 @@ mod tests {
             .build()
             .unwrap();
 
-        let expected = "Projection: TimestampNanosecond(1599566400000000000)\
+        let expected = "Projection: TimestampNanosecond(1599566400000000000) AS totimestamp(Utf8(\"2020-09-08T12:00:00+00:00\"))\
             \n  TableScan: test projection=None"
             .to_string();
         let actual = get_optimized_plan_formatted(&plan, &Utc::now());
@@ -824,7 +839,7 @@ mod tests {
             .build()
             .unwrap();
 
-        let expected = "Projection: Int32(0)\
+        let expected = "Projection: Int32(0) AS CAST(Utf8(\"0\") AS Int32)\
             \n  TableScan: test projection=None";
         let actual = get_optimized_plan_formatted(&plan, &Utc::now());
         assert_eq!(expected, actual);
@@ -873,7 +888,7 @@ mod tests {
         // expect the same timestamp appears in both exprs
         let actual = get_optimized_plan_formatted(&plan, &time);
         let expected = format!(
-            "Projection: TimestampNanosecond({}), TimestampNanosecond({}) AS t2\
+            "Projection: TimestampNanosecond({}) AS now(), TimestampNanosecond({}) AS t2\
             \n  TableScan: test projection=None",
             time.timestamp_nanos(),
             time.timestamp_nanos()
@@ -897,7 +912,8 @@ mod tests {
             .unwrap();
 
         let actual = get_optimized_plan_formatted(&plan, &time);
-        let expected = "Projection: NOT #test.a\
+        let expected =
+            "Projection: NOT #test.a AS Boolean(true) OR Boolean(false) != test.a\
                         \n  TableScan: test projection=None";
 
         assert_eq!(actual, expected);
@@ -929,7 +945,7 @@ mod tests {
 
         // Note that constant folder runs and folds the entire
         // expression down to a single constant (true)
-        let expected = "Filter: Boolean(true)\
+        let expected = "Filter: Boolean(true) AS CAST(now() AS Int64) < CAST(totimestamp(Utf8(\"2020-09-08T12:05:00+00:00\")) AS Int64) + Int32(50000)\
                         \n  TableScan: test projection=None";
         let actual = get_optimized_plan_formatted(&plan, &time);
 

datafusion/src/physical_plan/planner.rs

@@ -25,7 +25,7 @@ use super::{
 use crate::execution::context::ExecutionContextState;
 use crate::logical_plan::plan::{EmptyRelation, Filter, Projection, Window};
 use crate::logical_plan::{
-    unnormalize_cols, CrossJoin, DFSchema, Expr, LogicalPlan, Operator,
+    unalias, unnormalize_cols, CrossJoin, DFSchema, Expr, LogicalPlan, Operator,
     Partitioning as LogicalPartitioning, PlanType, Repartition, ToStringifiedPlan, Union,
     UserDefinedLogicalNode,
 };
@@ -339,7 +339,8 @@ impl DefaultPhysicalPlanner {
                     // doesn't know (nor should care) how the relation was
                     // referred to in the query
                     let filters = unnormalize_cols(filters.iter().cloned());
-                    source.scan(projection, batch_size, &filters, *limit).await
+                    let unaliased: Vec<Expr> = filters.into_iter().map(unalias).collect();
+                    source.scan(projection, batch_size, &unaliased, *limit).await
                 }
                 LogicalPlan::Values(Values {
                     values,
@@ -1340,7 +1341,7 @@ impl DefaultPhysicalPlanner {
         physical_input_schema: &Schema,
         ctx_state: &ExecutionContextState,
     ) -> Result<Arc<dyn AggregateExpr>> {
-        // unpack aliased logical expressions, e.g. "sum(col) as total"
+        // unpack (nested) aliased logical expressions, e.g. "sum(col) as total"
         let (name, e) = match e {
             Expr::Alias(sub_expr, alias) => (alias.clone(), sub_expr.as_ref()),
             _ => (physical_name(e)?, e),

datafusion/tests/sql.rs

@@ -1391,6 +1391,22 @@ async fn csv_query_approx_count() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test]
+async fn query_count_without_from() -> Result<()> {
+    let mut ctx = ExecutionContext::new();
+    let sql = "SELECT count(1 + 1)";
+    let actual = execute_to_batches(&mut ctx, sql).await;
+    let expected = vec![
+        "+----------------------------+",
+        "| COUNT(Int64(1) + Int64(1)) |",
+        "+----------------------------+",
+        "| 1                          |",
+        "+----------------------------+",
+    ];
+    assert_batches_eq!(expected, &actual);
+    Ok(())
+}
+
 #[tokio::test]
 async fn csv_query_array_agg() -> Result<()> {
     let mut ctx = ExecutionContext::new();
@@ -1663,12 +1679,12 @@ async fn csv_query_cast_literal() -> Result<()> {
     let actual = execute_to_batches(&mut ctx, sql).await;
 
     let expected = vec![
-        "+--------------------+------------+",
-        "| c12                | Float64(1) |",
-        "+--------------------+------------+",
-        "| 0.9294097332465232 | 1          |",
-        "| 0.3114712539863804 | 1          |",
-        "+--------------------+------------+",
+        "+--------------------+---------------------------+",
+        "| c12                | CAST(Int64(1) AS Float64) |",
+        "+--------------------+---------------------------+",
+        "| 0.9294097332465232 | 1                         |",
+        "| 0.3114712539863804 | 1                         |",
+        "+--------------------+---------------------------+",
     ];
 
     assert_batches_eq!(expected, &actual);
@@ -4410,11 +4426,11 @@ async fn query_without_from() -> Result<()> {
     let sql = "SELECT 1+2, 3/4, cos(0)";
     let actual = execute_to_batches(&mut ctx, sql).await;
     let expected = vec![
-        "+----------+----------+------------+",
-        "| Int64(3) | Int64(0) | Float64(1) |",
-        "+----------+----------+------------+",
-        "| 3        | 0        | 1          |",
-        "+----------+----------+------------+",
+        "+---------------------+---------------------+---------------+",
+        "| Int64(1) + Int64(2) | Int64(3) / Int64(4) | cos(Int64(0)) |",
+        "+---------------------+---------------------+---------------+",
+        "| 3                   | 0                   | 1             |",
+        "+---------------------+---------------------+---------------+",
     ];
     assert_batches_eq!(expected, &actual);
 
@@ -5865,11 +5881,11 @@ async fn case_with_bool_type_result() -> Result<()> {
     let sql = "select case when 'cpu' != 'cpu' then true else false end";
     let actual = execute_to_batches(&mut ctx, sql).await;
     let expected = vec![
-        "+----------------+",
-        "| Boolean(false) |",
-        "+----------------+",
-        "| false          |",
-        "+----------------+",
+        "+---------------------------------------------------------------------------------+",
+        "| CASE WHEN Utf8(\"cpu\") != Utf8(\"cpu\") THEN Boolean(true) ELSE Boolean(false) END |",
+        "+---------------------------------------------------------------------------------+",
+        "| false                                                                           |",
+        "+---------------------------------------------------------------------------------+",
     ];
     assert_batches_eq!(expected, &actual);
     Ok(())
@@ -5882,11 +5898,11 @@ async fn use_between_expression_in_select_query() -> Result<()> {
     let sql = "SELECT 1 NOT BETWEEN 3 AND 5";
     let actual = execute_to_batches(&mut ctx, sql).await;
     let expected = vec![
-        "+---------------+",
-        "| Boolean(true) |",
-        "+---------------+",
-        "| true          |",
-        "+---------------+",
+        "+--------------------------------------------+",
+        "| Int64(1) NOT BETWEEN Int64(3) AND Int64(5) |",
+        "+--------------------------------------------+",
+        "| true                                       |",
+        "+--------------------------------------------+",
     ];
     assert_batches_eq!(expected, &actual);