feat(subquery): support uncorrelated scalar subquery for where expr

src/binder/statement/mod.rs

@@ -95,11 +95,14 @@ impl Binder {
         let select_distinct = select.distinct;
 
         // bind where clause
-        let where_clause = select
+        let mut where_clause = select
             .selection
             .as_ref()
             .map(|expr| self.bind_expr(expr))
             .transpose()?;
+        if let Some(expr) = &mut where_clause {
+            self.rewrite_scalar_subquery(expr, &mut from_table)
+        }
 
         // bind group by clause
         let group_by = select

tests/planner/column-pruning.planner.sql

@@ -200,3 +200,28 @@ PhysicalProject: exprs [t1.a:Int64, (subquery_0.subquery_0_scalar_v0:Nullable(In
         PhysicalTableScan: table: #t1, columns: [b]
 */
 
+-- PushProjectThroughChild: column pruning across scalar subquery in where expr
+
+select t1.a, t1.b from t1 where a >= (select max(a) from t1);
+
+/*
+original plan:
+LogicalProject: exprs [t1.a:Int64, t1.b:Int64]
+  LogicalFilter: expr t1.a:Int64 >= subquery_0.subquery_0_scalar_v0:Nullable(Int64)
+    LogicalJoin: type Cross, cond None
+      LogicalTableScan: table: #t1, columns: [a, b, c]
+      LogicalProject: exprs [(Max(t1.a:Int64):Int64) as subquery_0.subquery_0_scalar_v0]
+        LogicalAgg: agg_funcs [Max(t1.a:Int64):Int64] group_by []
+          LogicalTableScan: table: #t1, columns: [a, b, c]
+
+optimized plan:
+PhysicalProject: exprs [t1.a:Int64, t1.b:Int64]
+  PhysicalFilter: expr t1.a:Int64 >= subquery_0.subquery_0_scalar_v0:Nullable(Int64)
+    PhysicalProject: exprs [t1.a:Nullable(Int64), t1.b:Nullable(Int64), subquery_0.subquery_0_scalar_v0:Nullable(Int64)]
+      PhysicalCrossJoin: type Cross
+        PhysicalTableScan: table: #t1, columns: [a, b]
+        PhysicalProject: exprs [(Max(t1.a:Int64):Int64) as subquery_0.subquery_0_scalar_v0]
+          PhysicalSimpleAgg: agg_funcs [Max(t1.a:Int64):Int64] group_by []
+            PhysicalTableScan: table: #t1, columns: [a]
+*/
+

tests/planner/column-pruning.yml

@@ -44,3 +44,8 @@
     select a, (select max(b) from t1) + (select min(b) from t1) as mix_b from t1;
   desc: |
     PushProjectThroughChild: column pruning across multiple scalar subquery
+
+- sql: |
+    select t1.a, t1.b from t1 where a >= (select max(a) from t1);
+  desc: |
+    PushProjectThroughChild: column pruning across scalar subquery in where expr

tests/slt/subquery.slt

@@ -71,3 +71,15 @@ select a, (select max(b) from t1) + (select min(b) from t1) as mix_b from t1;
 1 12
 2 12
 2 12
+
+query I
+select t1.a, t1.b from t1 where a >= (select max(a) from t1);
+----
+2 7
+2 8
+
+query I
+select t1.a, t1.b from t1 where a >= (select max(a) from t1) and b = (select max(b) from t1);
+----
+2 7
+2 8