Merge 'Fix EXISTS on LEFT JOIN null rows' from Duy Dang

Close #3890

Reviewed-by: Preston Thorpe <preston@turso.tech>

Closes #3914

core/translate/main_loop.rs

@@ -718,25 +718,6 @@ pub fn open_loop(
             }
         }
 
-        for subquery in subqueries.iter_mut().filter(|s| !s.has_been_evaluated()) {
-            assert!(subquery.correlated, "subquery must be correlated");
-            let eval_at = subquery.get_eval_at(join_order)?;
-
-            if eval_at != EvalAt::Loop(join_index) {
-                continue;
-            }
-
-            let plan = subquery.consume_plan(eval_at);
-
-            emit_non_from_clause_subquery(
-                program,
-                t_ctx,
-                *plan,
-                &subquery.query_type,
-                subquery.correlated,
-            )?;
-        }
-
         // First emit outer join conditions, if any.
         emit_conditions(
             program,
@@ -765,6 +746,25 @@ pub fn open_loop(
             }
         }
 
+        for subquery in subqueries.iter_mut().filter(|s| !s.has_been_evaluated()) {
+            assert!(subquery.correlated, "subquery must be correlated");
+            let eval_at = subquery.get_eval_at(join_order)?;
+
+            if eval_at != EvalAt::Loop(join_index) {
+                continue;
+            }
+
+            let plan = subquery.consume_plan(eval_at);
+
+            emit_non_from_clause_subquery(
+                program,
+                t_ctx,
+                *plan,
+                &subquery.query_type,
+                subquery.correlated,
+            )?;
+        }
+
         // Now we can emit conditions from the WHERE clause.
         // If the right table produces a NULL row, control jumps to the point where the match flag is set.
         // The WHERE clause conditions may reference columns from that row, so they cannot be emitted

testing/subquery.test

@@ -120,6 +120,17 @@ do_execsql_test nested-subquery-cte {
     select sub.loudest_hat from sub;
 } {HAT!!!}
 
+do_execsql_test_on_specific_db {:memory:} correlated-left-join-exists {
+    create table t(a);
+    create table s(a);
+    insert into t values (1);
+    select t.a
+      from t
+      left join s
+        on t.a = s.a
+     where exists (select 1 where s.a is null);
+} {1}
+
 do_execsql_test subquery-orderby-limit {
     select upper(sub.loud_name) as loudest_name 
     from (
@@ -987,4 +998,4 @@ do_execsql_test_in_memory_any_error subquery-vector-in-function-call {
     insert into t1 values (1);
     insert into t2 values (1, 2);
     select abs((select y, z from t2)) from t1;
-}
+}