Fixed LP bug #725050.

The bug in the function print_keyuse() caused crashes if
hash join could be used. It happened because the function
ignored the fact that KEYUSE structures could be created
for hash joins as well. 

mysql-test/r/join_cache.result

@@ -4967,3 +4967,21 @@ SET SESSION join_cache_level = DEFAULT;
 SET SESSION join_buffer_size = DEFAULT;
 DROP TABLE t1,t2;
 set @@optimizer_switch=@save_optimizer_switch;
+#
+# Bug #725050: print keyuse info when  hash join is used 
+#
+create table t1 (a int, b int);
+insert into t1 values (2,2), (1,1);
+create table t2 (a int);
+insert into t2 values (2), (3);
+set session join_cache_level=3;
+set @@debug = 'd:t:O,/tmp/trace.out';
+explain select t1.b from t1,t2 where t1.b=t2.a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	Using where
+1	SIMPLE	t2	hash_ALL	NULL	#hash#$hj	5	test.t1.b	2	Using where; Using join buffer (flat, BNLH join)
+select t1.b from t1,t2 where t1.b=t2.a;
+b
+2
+set session join_cache_level=default;
+drop table t1,t2;

mysql-test/t/join_cache.test

@@ -3100,3 +3100,21 @@ DROP TABLE t1,t2;
 
 # this must be the last command in the file
 set @@optimizer_switch=@save_optimizer_switch;
+
+--echo #
+--echo # Bug #725050: print keyuse info when  hash join is used 
+--echo #
+
+create table t1 (a int, b int);
+insert into t1 values (2,2), (1,1);
+create table t2 (a int);
+insert into t2 values (2), (3);
+
+set session join_cache_level=3;
+set @@debug = 'd:t:O,/tmp/trace.out';
+
+explain select t1.b from t1,t2 where t1.b=t2.a;
+select t1.b from t1,t2 where t1.b=t2.a;
+
+set session join_cache_level=default;
+drop table t1,t2;

sql/sql_test.cc

@@ -231,14 +231,18 @@ void print_keyuse(KEYUSE *keyuse)
   char buff[256];
   char buf2[64]; 
   const char *fieldname;
+  JOIN_TAB *join_tab= keyuse->table->reginfo.join_tab;
+  KEY *key_info= join_tab->get_keyinfo_by_key_no(keyuse->key);
   String str(buff,(uint32) sizeof(buff), system_charset_info);
   str.length(0);
   keyuse->val->print(&str, QT_ORDINARY);
   str.append('\0');
-  if (keyuse->keypart == FT_KEYPART)
+  if (keyuse->is_for_hash_join())
+    fieldname= keyuse->table->field[keyuse->keypart]->field_name;
+  else if (keyuse->keypart == FT_KEYPART)
     fieldname= "FT_KEYPART";
   else
-    fieldname= keyuse->table->key_info[keyuse->key].key_part[keyuse->keypart].field->field_name;
+    fieldname= key_info->key_part[keyuse->keypart].field->field_name;
   longlong2str(keyuse->used_tables, buf2, 16, 0); 
   DBUG_LOCK_FILE;
   fprintf(DBUG_FILE, "KEYUSE: %s.%s=%s  optimize: %u  used_tables: %s "