Fix a problem with the query optimizer for LIMIT/OFFSET queries when

underlying query is a UNION ALL and both arms of the UNION ALL are
subqueries with an ORDER BY clause.  This bug was reported at
[forum:/forumpost/6b5e9188f0657616|forum post 6b5e9188f0657616].  The
problem was introduced in 2015 (SQLite version 3.9.0) by check-in
[4b631364354068af].  See also ticket [b65cb2c8d91f6685].

FossilOrigin-Name: 6c806f64bbc9e98891bad0868575ee2ec5d0951ceb0c71d3ed417b45d5f27561

test/offset1.test

@@ -156,6 +156,47 @@ do_execsql_test offset1-1.4.9 {
   LIMIT 9 OFFSET 1;
 } {2 b 3 c 4 d 5 e 6 w 7 x 8 y 9 z}
 
-
+# 2022-08-04
+# https://sqlite.org/forum/forumpost/6b5e9188f0657616
+#
+do_execsql_test offset1-2.0 {
+  CREATE TABLE employees (
+    id integer primary key,
+    name text,
+    city text,
+    department text,
+    salary integer
+  );
+  INSERT INTO employees VALUES
+    (11,'Diane','London','hr',70),
+    (12,'Bob','London','hr',78),
+    (21,'Emma','London','it',84),
+    (22,'Grace','Berlin','it',90),
+    (23,'Henry','London','it',104),
+    (24,'Irene','Berlin','it',104),
+    (25,'Frank','Berlin','it',120),
+    (31,'Cindy','Berlin','sales',96),
+    (32,'Dave','London','sales',96),
+    (33,'Alice','Berlin','sales',100);
+  CREATE VIEW v AS
+    SELECT * FROM (
+      SELECT * FROM employees 
+       WHERE salary < 100
+       ORDER BY salary desc)
+     UNION ALL 
+     SELECT * FROM (
+       SELECT * FROM employees
+       WHERE salary >= 100
+       ORDER BY salary asc);
+} {}
+do_execsql_test offset1-2.1 {
+  SELECT * FROM v LIMIT 5 OFFSET 2;
+} {
+  22  Grace  Berlin  it      90
+  21  Emma   London  it      84
+  12  Bob    London  hr      78
+  11  Diane  London  hr      70
+  33  Alice  Berlin  sales   100
+}
 
 finish_test