Fixed an unlikely optimizer bug that casued a core dump in pt_range.cc::sel_cmp()

mysql-test/r/join.result:
  Test of range optimizer bug
mysql-test/t/join.test:
  Test of range optimizer bug
sql/sql_rename.cc:
  Added missing DEBUG_PRINT()

mysql-test/r/join.result

@@ -37,3 +37,7 @@ COUNT(t1.Title)
 t1_id	t2_id	type	cost_unit	min_value	max_value	t3_id	item_id	id	name
 22	1	Percent	Cost	100	-1	6	291	1	s1
 23	1	Percent	Cost	100	-1	21	291	1	s1
+rate_code	base_rate
+cust	20
+rate_code	base_rate
+cust	20

mysql-test/t/join.test

@@ -219,3 +219,27 @@ CREATE TABLE t2 (
 INSERT INTO t2 VALUES (1,'s1'),(2,'s2'),(3,'s3'),(4,'s4'),(5,'s5');
 select t1.*, t2.*  from t1, t2 where t2.id=t1.t2_id limit 2;
 drop table t1,t2;
+
+#
+# Bug in range optimiser with MAYBE_KEY
+#
+
+CREATE TABLE t1 (
+  siteid varchar(25) NOT NULL default '',
+  emp_id varchar(30) NOT NULL default '',
+  rate_code varchar(10) default NULL,
+  UNIQUE KEY site_emp (siteid,emp_id),
+  KEY siteid (siteid)
+) TYPE=MyISAM;
+INSERT INTO t1 VALUES ('rivercats','psmith','cust'), ('rivercats','KWalker','cust');
+CREATE TABLE t2 (
+  siteid varchar(25) NOT NULL default '',
+  rate_code varchar(10) NOT NULL default '',
+  base_rate float NOT NULL default '0',
+  PRIMARY KEY  (siteid,rate_code),
+  FULLTEXT KEY rate_code (rate_code)
+) TYPE=MyISAM;
+INSERT INTO t2 VALUES ('rivercats','cust',20);
+SELECT emp.rate_code, lr.base_rate FROM t1 AS emp LEFT JOIN t2 AS lr USING (siteid, rate_code) WHERE emp.emp_id = 'psmith' AND lr.siteid = 'rivercats';
+SELECT emp.rate_code, lr.base_rate FROM t1 AS emp LEFT JOIN t2 AS lr USING (siteid, rate_code) WHERE lr.siteid = 'rivercats' AND emp.emp_id = 'psmith';
+drop table t1,t2;

sql/opt_range.cc

@@ -1341,7 +1341,8 @@ key_and(SEL_ARG *key1,SEL_ARG *key2,uint clone_flag)
   }
 
   if (((clone_flag & CLONE_KEY2_MAYBE) &&
-       !(clone_flag & CLONE_KEY1_MAYBE)) ||
+       !(clone_flag & CLONE_KEY1_MAYBE) &&
+       key2->type != SEL_ARG::MAYBE_KEY) ||
       key1->type == SEL_ARG::MAYBE_KEY)
   {						// Put simple key in key2
     swap(SEL_ARG *,key1,key2);
@@ -1369,7 +1370,10 @@ key_and(SEL_ARG *key1,SEL_ARG *key2,uint clone_flag)
     {
       key1->maybe_smaller();
       if (key2->next_key_part)
+      {
+	key1->use_count--;			// Incremented in and_all_keys
 	return and_all_keys(key1,key2,clone_flag);
+      }
       key2->use_count--;			// Key2 doesn't have a tree
     }
     return key1;
@@ -2068,7 +2072,7 @@ void SEL_ARG::test_use_count(SEL_ARG *root)
 {
   if (this == root && use_count != 1)
   {
-    sql_print_error("Use_count: Wrong count %lu for root",use_count);
+    sql_print_error("Note: Use_count: Wrong count %lu for root",use_count);
     return;
   }
   if (this->type != SEL_ARG::KEY_RANGE)
@@ -2082,7 +2086,7 @@ void SEL_ARG::test_use_count(SEL_ARG *root)
       ulong count=count_key_part_usage(root,pos->next_key_part);
       if (count > pos->next_key_part->use_count)
       {
-	sql_print_error("Use_count: Wrong count for key at %lx, %lu should be %lu",
+	sql_print_error("Note: Use_count: Wrong count for key at %lx, %lu should be %lu",
 			pos,pos->next_key_part->use_count,count);
 	return;
       }
@@ -2090,7 +2094,7 @@ void SEL_ARG::test_use_count(SEL_ARG *root)
     }
   }
   if (e_count != elements)
-    sql_print_error("Wrong use count: %u for tree at %lx", e_count,
+    sql_print_error("Warning: Wrong use count: %u for tree at %lx", e_count,
 		    (gptr) this);
 }
 

sql/sql_rename.cc

@@ -122,7 +122,7 @@ rename_tables(THD *thd, TABLE_LIST *table_list, bool skip_error)
     if (!access(name,F_OK))
     {
       my_error(ER_TABLE_EXISTS_ERROR,MYF(0),name);
-      return ren_table;				// This can't be skipped
+      DBUG_RETURN(ren_table);			// This can't be skipped
     }
     sprintf(name,"%s/%s/%s%s",mysql_data_home,
 	    ren_table->db,ren_table->real_name,
@@ -131,7 +131,7 @@ rename_tables(THD *thd, TABLE_LIST *table_list, bool skip_error)
     {
       my_error(ER_FILE_NOT_FOUND, MYF(0), name, my_errno);
       if (!skip_error)
-	return ren_table;
+	DBUG_RETURN(ren_table);
     }
     else if (mysql_rename_table(table_type,
 				ren_table->db, ren_table->real_name,