database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-29 05:21:33 +03:00
Code Activity

Bug #52593 SHOW CREATE TABLE is blocked if table is locked

Browse Source 
for write by another connection

The problem was that if a table was locked in one connection by
LOCK TABLES ... WRITE, REPAIR TABLE or OPTIMIZE TABLE, SHOW CREATE
TABLE from another connection would be blocked. As SHOW CREATE TABLE
only reads metadata about the table, such blocking is not needed.

The problem was that when SHOW CREATE TABLE tried to get a metadata
lock on the table in order to open it, it used the wrong type of
metadata lock request. It used MDL_SHARED_READ which is used when
the intent is to read both table metadata and table data. Instead
it should have used MDL_SHARED_HIGH_PRIO which signifies an intent
to only read metadata.

This patch fixes the problem by making sure SHOW CREATE TABLE uses
the MDL_SHARED_HIGH_PRIO metadata lock request type when trying to
open the table. The patch also fixes a similar problem with the
mysql_list_fields API call.

Test case added to show_check.test.
This commit is contained in:
Jon Olav Hauglid
2010-04-14 09:40:45 +02:00
parent 7e6eddd374
commit d18275c2c2
3 changed files with 50 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
sql/sql_show.cc
View File

@ -1,4 +1,4 @@
/* Copyright 2000-2008 MySQL AB, 2008-2009 Sun Microsystems, Inc.
/* Copyright 2000, 2010 Oracle and/or its affiliates. All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@ -11,7 +11,7 @@
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
/* Function with list databases, tables or fields */
@ -641,7 +641,9 @@ mysqld_show_create(THD *thd, TABLE_LIST *table_list)
{
Show_create_error_handler view_error_suppressor(thd, table_list);
thd->push_internal_handler(&view_error_suppressor);
bool error= open_normal_and_derived_tables(thd, table_list, 0);
bool error=
open_normal_and_derived_tables(thd, table_list,
MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL);
thd->pop_internal_handler();
if (error && (thd->killed || thd->is_error()))
DBUG_RETURN(TRUE);
@ -815,7 +817,8 @@ mysqld_list_fields(THD *thd, TABLE_LIST *table_list, const char *wild)
DBUG_ENTER("mysqld_list_fields");
DBUG_PRINT("enter",("table: %s",table_list->table_name));
if (open_normal_and_derived_tables(thd, table_list, 0))
if (open_normal_and_derived_tables(thd, table_list,
MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL))
DBUG_VOID_RETURN;
table= table_list->table;