Fix for bug #11762012 - "54553: INNODB ASSERTS IN

HA_INNOBASE::UPDATE_ROW, TEMPORARY TABLE, TABLE LOCK".

Attempt to update an InnoDB temporary table under LOCK TABLES
led to assertion failure in both debug and production builds
if this temporary table was explicitly locked for READ. The
same scenario works fine for MyISAM temporary tables.

The assertion failure was caused by discrepancy between lock
that was requested on the rows of temporary table at LOCK TABLES
time and by update operation. Since SQL-layer requested a
read-lock at LOCK TABLES time InnoDB engine assumed that upcoming
statements which are going to be executed under LOCK TABLES will
only read table and therefore should acquire only S-lock.
An update operation broken this assumption by requesting X-lock.

Possible approaches to fixing this problem are:

1) Skip locking of temporary tables as locking doesn't make any
   sense for connection-local objects.
2) Prohibit changing of temporary table locked by LOCK TABLES ...
   READ.

Unfortunately both of these approaches have drawbacks which make
them unviable for stable versions of server.

So this patch takes another approach and changes code in such way
that LOCK TABLES for a temporary table will always request write
lock. In 5.5 version of this patch switch from read lock to write
lock is done on SQL-layer.

1 files changed, 62 insertions, 21 deletions

diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
index 4f5bce3e8af..44a9243d8f5 100644
--- a/sql/sql_parse.cc
+++ b/sql/sql_parse.cc
@@ -1749,6 +1749,67 @@ bool sp_process_definer(THD *thd)
 
 
 /**
+  Auxiliary call that opens and locks tables for LOCK TABLES statement
+  and initializes the list of locked tables.
+
+  @param thd     Thread context.
+  @param tables  List of tables to be locked.
+
+  @return FALSE in case of success, TRUE in case of error.
+*/
+
+static bool lock_tables_open_and_lock_tables(THD *thd, TABLE_LIST *tables)
+{
+  Lock_tables_prelocking_strategy lock_tables_prelocking_strategy;
+  uint counter;
+  TABLE_LIST *table;
+
+  thd->in_lock_tables= 1;
+
+  if (open_tables(thd, &tables, &counter, 0, &lock_tables_prelocking_strategy))
+    goto err;
+
+  /*
+    We allow to change temporary tables even if they were locked for read
+    by LOCK TABLES. To avoid a discrepancy between lock acquired at LOCK
+    TABLES time and by the statement which is later executed under LOCK TABLES
+    we ensure that for temporary tables we always request a write lock (such
+    discrepancy can cause problems for the storage engine).
+    We don't set TABLE_LIST::lock_type in this case as this might result in
+    extra warnings from THD::decide_logging_format() even though binary logging
+    is totally irrelevant for LOCK TABLES.
+  */
+  for (table= tables; table; table= table->next_global)
+    if (!table->placeholder() && table->table->s->tmp_table)
+      table->table->reginfo.lock_type= TL_WRITE;
+
+  if (lock_tables(thd, tables, counter, 0) ||
+      thd->locked_tables_list.init_locked_tables(thd))
+    goto err;
+
+  thd->in_lock_tables= 0;
+
+  return FALSE;
+
+err:
+  thd->in_lock_tables= 0;
+
+  trans_rollback_stmt(thd);
+  /*
+    Need to end the current transaction, so the storage engine (InnoDB)
+    can free its locks if LOCK TABLES locked some tables before finding
+    that it can't lock a table in its list
+  */
+  trans_commit_implicit(thd);
+  /* Close tables and release metadata locks. */
+  close_thread_tables(thd);
+  DBUG_ASSERT(!thd->locked_tables_mode);
+  thd->mdl_context.release_transactional_locks();
+  return TRUE;
+}
+
+
+/**
   Execute command saved in thd and lex->sql_command.
 
   @param thd                       Thread handle
@@ -3093,31 +3154,11 @@ end_with_restore_list:
       goto error;
 
     thd->variables.option_bits|= OPTION_TABLE_LOCK;
-    thd->in_lock_tables=1;
 
-    {
-      Lock_tables_prelocking_strategy lock_tables_prelocking_strategy;
-
-      res= (open_and_lock_tables(thd, all_tables, FALSE, 0,
-                                 &lock_tables_prelocking_strategy) ||
-            thd->locked_tables_list.init_locked_tables(thd));
-    }
-
-    thd->in_lock_tables= 0;
+    res= lock_tables_open_and_lock_tables(thd, all_tables);
 
     if (res)
     {
-      trans_rollback_stmt(thd);
-      /*
-        Need to end the current transaction, so the storage engine (InnoDB)
-        can free its locks if LOCK TABLES locked some tables before finding
-        that it can't lock a table in its list
-      */
-      trans_commit_implicit(thd);
-      /* Close tables and release metadata locks. */
-      close_thread_tables(thd);
-      DBUG_ASSERT(!thd->locked_tables_mode);
-      thd->mdl_context.release_transactional_locks();
       thd->variables.option_bits&= ~(OPTION_TABLE_LOCK);
     }
     else