Enhance the query planner so that it looks at multiple solutions to OR

expressions in the WHERE clause.

FossilOrigin-Name: 5e19d054105fb16ff52d265d48cc87a418603f6f

test/where2.test

@@ -699,5 +699,16 @@ do_test where2-11.4 {
   }
 } {4 8 10}
 
+# Verify that the OR clause is used in an outer loop even when
+# the OR clause scores slightly better on an inner loop.
+do_execsql_test where2-12.1 {
+  CREATE TABLE t12(x INTEGER PRIMARY KEY, y);
+  CREATE INDEX t12y ON t12(y);
+  EXPLAIN QUERY PLAN
+    SELECT a.x, b.x
+      FROM t12 AS a JOIN t12 AS b ON a.y=b.x
+     WHERE (b.x=$abc OR b.y=$abc);
+} {/.*SEARCH TABLE t12 AS b .*SEARCH TABLE t12 AS b .*/}
+
 
 finish_test