Bug #28476: force index on a disabled myisam index gives error 124

When processing the USE/FORCE index hints
the optimizer was not checking if the indexes 
specified are enabled (see ALTER TABLE).
Fixed by:
 Backporting the fix for bug 20604 to 5.0


mysql-test/r/key.result:
  Test for BUG 20604.
  The important part of the test is the explain output that 
  tests what indexes are used.
mysql-test/r/myisam.result:
  Bug #28476: test cases
mysql-test/t/key.test:
  Bug 20604: 
  The minimal test case that reveals the bug. The optimizer for 
  aggregates relies on keys disabled with ALTER TABLE ... DISABLE KEYS
  not being in the set TABLE::keys_in_use_for_query.
  When the execution engine tries to use a disabled index, MyISAM
  returns an error.
mysql-test/t/myisam.test:
  Bug #28476: test cases
sql/sql_base.cc:
  Bug #28476: 
   - Ignore disabled indexes in USE/FORCE index
sql/sql_select.cc:
  Bug 20604 : The intersection operation between table->s->keys_in_use 
  and table->keys_in_use_for_query is no longer necessary.
  We can trust that the latter is a subset of the former.
sql/table.h:
  Bug 20604:
  Added comments to TABLE_SHARE::keys_in_use and
  TABLE::keys_in_use_for_query.

1 files changed, 6 insertions, 1 deletions

diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index 6e6611d54d2..59532b9fe96 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -4811,7 +4811,12 @@ bool setup_tables(THD *thd, Name_resolution_context *context,
       get_key_map_from_key_list(&map, table, table_list->use_index);
       if (map.is_set_all())
 	DBUG_RETURN(1);
-      table->keys_in_use_for_query=map;
+      /* 
+	 Don't introduce keys in keys_in_use_for_query that weren't there 
+	 before. FORCE/USE INDEX should not add keys, it should only remove
+	 all keys except the key(s) specified in the hint.
+      */
+      table->keys_in_use_for_query.intersect(map);
     }
     if (table_list->ignore_index)
     {