diff --git a/mysql-test/r/show_check.result b/mysql-test/r/show_check.result index ef2277fef38..f49366cbf08 100644 --- a/mysql-test/r/show_check.result +++ b/mysql-test/r/show_check.result @@ -1466,3 +1466,24 @@ t1 CREATE TABLE `t1` ( # Switching to connection 'default'. UNLOCK TABLES; DROP TABLE t1; +# +# Bug#54905 Connection with WRITE lock cannot ALTER table due to +# concurrent SHOW CREATE +# +DROP TABLE IF EXISTS t1; +CREATE TABLE t1(a INT); +# Connection con1 +LOCK TABLE t1 WRITE; +# Connection default +START TRANSACTION; +SHOW CREATE TABLE t1; +Table Create Table +t1 CREATE TABLE `t1` ( + `a` int(11) DEFAULT NULL +) ENGINE=MyISAM DEFAULT CHARSET=latin1 +# Connection con1 +ALTER TABLE t1 CHARACTER SET = utf8; +UNLOCK TABLES; +# Connection default +COMMIT; +DROP TABLE t1; diff --git a/mysql-test/t/show_check.test b/mysql-test/t/show_check.test index fa003c2fe69..89a43f24296 100644 --- a/mysql-test/t/show_check.test +++ b/mysql-test/t/show_check.test @@ -1246,6 +1246,39 @@ UNLOCK TABLES; DROP TABLE t1; +--echo # +--echo # Bug#54905 Connection with WRITE lock cannot ALTER table due to +--echo # concurrent SHOW CREATE +--echo # + +--disable_warnings +DROP TABLE IF EXISTS t1; +--enable_warnings + +CREATE TABLE t1(a INT); + +--echo # Connection con1 +connect (con1,localhost,root); +LOCK TABLE t1 WRITE; + +--echo # Connection default +connection default; +START TRANSACTION; +SHOW CREATE TABLE t1; + +--echo # Connection con1 +connection con1; +# Used to block +ALTER TABLE t1 CHARACTER SET = utf8; +UNLOCK TABLES; + +--echo # Connection default +connection default; +COMMIT; +disconnect con1; +DROP TABLE t1; + + # Wait till all disconnects are completed --source include/wait_until_count_sessions.inc diff --git a/sql/sql_show.cc b/sql/sql_show.cc index a8ae5832a2a..8647237ce72 100644 --- a/sql/sql_show.cc +++ b/sql/sql_show.cc @@ -649,22 +649,30 @@ mysqld_show_create(THD *thd, TABLE_LIST *table_list) Protocol *protocol= thd->protocol; char buff[2048]; String buffer(buff, sizeof(buff), system_charset_info); + List field_list; + bool error= TRUE; DBUG_ENTER("mysqld_show_create"); DBUG_PRINT("enter",("db: %s table: %s",table_list->db, table_list->table_name)); + /* + Metadata locks taken during SHOW CREATE should be released when + the statmement completes as it is an information statement. + */ + MDL_ticket *mdl_savepoint= thd->mdl_context.mdl_savepoint(); + /* We want to preserve the tree for views. */ thd->lex->view_prepare_mode= TRUE; { Show_create_error_handler view_error_suppressor(thd, table_list); thd->push_internal_handler(&view_error_suppressor); - bool error= + bool open_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); + if (open_error && (thd->killed || thd->is_error())) + goto exit; } /* TODO: add environment variables show when it become possible */ @@ -672,7 +680,7 @@ mysqld_show_create(THD *thd, TABLE_LIST *table_list) { my_error(ER_WRONG_OBJECT, MYF(0), table_list->db, table_list->table_name, "VIEW"); - DBUG_RETURN(TRUE); + goto exit; } buffer.length(0); @@ -684,9 +692,8 @@ mysqld_show_create(THD *thd, TABLE_LIST *table_list) view_store_create_info(thd, table_list, &buffer) : store_create_info(thd, table_list, &buffer, NULL, FALSE /* show_database */))) - DBUG_RETURN(TRUE); + goto exit; - List field_list; if (table_list->view) { field_list.push_back(new Item_empty_string("View",NAME_CHAR_LEN)); @@ -707,7 +714,8 @@ mysqld_show_create(THD *thd, TABLE_LIST *table_list) if (protocol->send_result_set_metadata(&field_list, Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF)) - DBUG_RETURN(TRUE); + goto exit; + protocol->prepare_for_resend(); if (table_list->view) protocol->store(table_list->view_name.str, system_charset_info); @@ -735,10 +743,16 @@ mysqld_show_create(THD *thd, TABLE_LIST *table_list) protocol->store(buffer.ptr(), buffer.length(), buffer.charset()); if (protocol->write()) - DBUG_RETURN(TRUE); + goto exit; + error= FALSE; my_eof(thd); - DBUG_RETURN(FALSE); + +exit: + close_thread_tables(thd); + /* Release any metadata locks taken during SHOW CREATE. */ + thd->mdl_context.rollback_to_savepoint(mdl_savepoint); + DBUG_RETURN(error); } bool mysqld_show_create_db(THD *thd, char *dbname,