bk commit into 5.1 tree (kostja:1.2533) BUG#21074

[konstantin]

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ChangeSet@stripped, 2007-07-16 15:57:20+04:00, kostja@bodhi.(none) +1 -0
  A follow up after the fix for Bug#21074 - fix NDB tests breaking on
  asserts.
  The patch for Bug#21074 replaces acquisition of the global LOCK_open lock
  with exclusive locks on table names in such operations ad DROP TABLE
  and RENAME TABLE.
  Unfortunately, NDB internally assumes that LOCK_open is acquired and
  tries to release it.
  This dependency should be fixed by a separate (and significant in size)
  patch. For now we just satisfy it - after all, the original
  goal of the patch for Bug#21074 was to move query_cache_invalidate
  outside of the scope of LOCK_open, and we still can do that.
  
  This fixes some failing NDB tests in the runtime tree.

  sql/sql_rename.cc@stripped, 2007-07-16 15:57:17+04:00, kostja@bodhi.(none) +11 -1
    Move release of LOCK_open after ha_ndbcluster::rename_tables to
    satisfy an assert in ndb_log_schema_op.

diff -Nrup a/sql/sql_rename.cc b/sql/sql_rename.cc
--- a/sql/sql_rename.cc	2007-07-02 23:00:12 +04:00
+++ b/sql/sql_rename.cc	2007-07-16 15:57:17 +04:00
@@ -150,7 +150,6 @@ bool mysql_rename_tables(THD *thd, TABLE
     pthread_mutex_unlock(&LOCK_open);
     goto err;
   }
-  pthread_mutex_unlock(&LOCK_open);
 
   error=0;
   if ((ren_table=rename_tables(thd,table_list,0)))
@@ -174,6 +173,17 @@ bool mysql_rename_tables(THD *thd, TABLE
 
     error= 1;
   }
+  /*
+    An exclusive lock on table names is satisfactory to ensure
+    no other thread accesses this table.
+    However, NDB assumes that handler::rename_tables is called under
+    LOCK_open. And it indeed is, from ALTER TABLE.
+    TODO: remove this limitation.
+    We still should unlock LOCK_open as early as possible, to provide
+    higher concurrency - query_cache_invalidate can take minutes to
+    complete.
+  */
+  pthread_mutex_unlock(&LOCK_open);
 
   /* Lets hope this doesn't fail as the result will be messy */ 
   if (!silent && !error)