Only continue an ORDER BY optimization into inner loops if the equality

constraints on the inner loop match terms of an outer ordered index that
are actually used by the ORDER BY clause.

FossilOrigin-Name: b0e7b4df6c2a8c479f8d210bde50c737eaa248f0

test/orderby1.test

@@ -170,14 +170,14 @@ do_test 2.0 {
       name TEXT,
       UNIQUE(aid, tn)
     );
-    INSERT INTO album VALUES(1, '1-one'), (2, '2-two'), (3, '3-three');
+    INSERT INTO album VALUES(1, '1-one'), (20, '2-two'), (3, '3-three');
     INSERT INTO track VALUES
-        (1, 1, 'one-a'),
-        (2, 2, 'two-b'),
-        (3, 3, 'three-c'),
-        (1, 3, 'one-c'),
-        (2, 1, 'two-a'),
-        (3, 1, 'three-a');
+        (1,  1, 'one-a'),
+        (20, 2, 'two-b'),
+        (3,  3, 'three-c'),
+        (1,  3, 'one-c'),
+        (20, 1, 'two-a'),
+        (3,  1, 'three-a');
     COMMIT;
   }
 } {}
@@ -194,6 +194,18 @@ do_test 2.1b {
     EXPLAIN QUERY PLAN
     SELECT name FROM album JOIN track USING (aid) ORDER BY title, tn
   }
+} {/ORDER BY/}  ;# ORDER BY required because of missing aid term in ORDER BY
+
+do_test 2.1c {
+  db eval {
+    SELECT name FROM album JOIN track USING (aid) ORDER BY title, aid, tn
+  }
+} {one-a one-c two-a two-b three-a three-c}
+do_test 2.1d {
+  db eval {
+    EXPLAIN QUERY PLAN
+    SELECT name FROM album JOIN track USING (aid) ORDER BY title, aid, tn
+  }
 } {~/ORDER BY/}  ;# ORDER BY optimized out
 
 # The same query with ORDER BY clause optimization disabled via + operators
@@ -284,7 +296,7 @@ do_test 2.6c {
     EXPLAIN QUERY PLAN
     SELECT name FROM album JOIN track USING (aid) ORDER BY title DESC, tn DESC
   }
-} {~/ORDER BY/}  ;# ORDER BY optimized-out
+} {/ORDER BY/}  ;# ORDER BY required
 
 
 # Generate another test dataset, but this time using mixed ASC/DESC indices.