Fixed LP bug #933117.

The bug was fixed with the code back-ported from the patch for LP bug 800184
pushed into mariadb-5.3.

mysql-test/r/range.result

@@ -1768,3 +1768,18 @@ SELECT * FROM t1, t1 as t2 WHERE t1.i4 BETWEEN t2.pk AND t2.pk;
 pk	i4	pk	i4
 DROP TABLE t1;
 End of 5.1 tests
+#
+# LP Bug #533117: Wrong use_count in SEL_ARG trees
+#   (Bug #58731)
+#
+create table t1 (a int, b int, c int, key idx (a,b,c));
+insert into t1 values (0,0,0), (2,2,0), (1,1,1), (2,2,1);
+explain
+select * from t1 force index (idx) where a >=1 and c <= 1 and a=b and b > 1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	idx	idx	5	NULL	3	Using where; Using index
+select * from t1 force index (idx) where a >=1 and c <= 1 and a=b and b > 1;
+a	b	c
+2	2	0
+2	2	1
+drop table t1;

mysql-test/t/range.test

@@ -1393,3 +1393,17 @@ SELECT * FROM t1, t1 as t2 WHERE t1.i4 BETWEEN t2.pk AND t2.pk;
 DROP TABLE t1;
 
 --echo End of 5.1 tests
+
+--echo #
+--echo # LP Bug #533117: Wrong use_count in SEL_ARG trees
+--echo #   (Bug #58731)
+--echo #
+
+create table t1 (a int, b int, c int, key idx (a,b,c));
+insert into t1 values (0,0,0), (2,2,0), (1,1,1), (2,2,1);
+
+explain
+select * from t1 force index (idx) where a >=1 and c <= 1 and a=b and b > 1;
+select * from t1 force index (idx) where a >=1 and c <= 1 and a=b and b > 1;
+
+drop table t1;

sql/opt_range.cc

@@ -498,6 +498,11 @@ class SEL_ARG :public Sql_alloc
 	  pos->increment_use_count(count);
     }
   }
+  void incr_refs()
+  {
+    increment_use_count(1);
+    use_count++;
+  }
   void free_tree()
   {
     for (SEL_ARG *pos=first(); pos ; pos=pos->next)
@@ -6475,8 +6480,8 @@ key_and(RANGE_OPT_PARAM *param, SEL_ARG *key1, SEL_ARG *key2, uint clone_flag)
       continue;
     SEL_ARG *next=key_and(param, e1->next_key_part, e2->next_key_part,
                           clone_flag);
-    e1->increment_use_count(1);
-    e2->increment_use_count(1);
+    e1->incr_refs();
+    e2->incr_refs();
     if (!next || next->type != SEL_ARG::IMPOSSIBLE)
     {
       SEL_ARG *new_arg= e1->clone_and(e2);