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Backport of revno: 2617.71.1

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Bug#42546 Backup: RESTORE fails, thinking it finds an existing table

The problem occured when a MDL locking conflict happened for a non-existent 
table between a CREATE and a INSERT statement. The code for CREATE 
interpreted this lock conflict to mean that the table existed, 
which meant that the statement failed when it should not have.
The problem could occur for CREATE TABLE, CREATE TABLE LIKE and
ALTER TABLE RENAME.

This patch fixes the problem for CREATE TABLE and CREATE TABLE LIKE.
It is based on code backported from the mysql-6.1-fk tree written
by Dmitry Lenev. CREATE now uses normal open_and_lock_tables() code 
to acquire exclusive locks. This means that for the test case in the bug 
description, CREATE will wait until INSERT completes so that it can 
get the exclusive lock. This resolves the reported bug.

The patch also prohibits CREATE TABLE and CREATE TABLE LIKE under 
LOCK TABLES. Note that this is an incompatible change and must 
be reflected in the documentation. Affected test cases have been
updated.

mdl_sync.test contains tests for CREATE TABLE and CREATE TABLE LIKE.

Fixing the issue for ALTER TABLE RENAME is beyond the scope of this
patch. ALTER TABLE cannot be prohibited from working under LOCK TABLES
as this could seriously impact customers and a proper fix would require
a significant rewrite.
This commit is contained in:
Jon Olav Hauglid
2009-12-10 11:53:20 +01:00
parent f3bc2406b0
commit 5e1dfa4c06
21 changed files with 465 additions and 415 deletions
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75
sql/sql_insert.cc
View File

@ -3415,46 +3415,43 @@ void select_insert::abort() {
CREATE TABLE (SELECT) ...
***************************************************************************/
/*
/**
Create table from lists of fields and items (or just return TABLE
object for pre-opened existing table).
SYNOPSIS
create_table_from_items()
thd in Thread object
create_info in Create information (like MAX_ROWS, ENGINE or
temporary table flag)
create_table in Pointer to TABLE_LIST object providing database
and name for table to be created or to be open
alter_info in/out Initial list of columns and indexes for the table
to be created
items in List of items which should be used to produce rest
of fields for the table (corresponding fields will
be added to the end of alter_info->create_list)
lock out Pointer to the MYSQL_LOCK object for table created
(or open temporary table) will be returned in this
parameter. Since this table is not included in
THD::lock caller is responsible for explicitly
unlocking this table.
hooks
@param thd [in] Thread object
@param create_info [in] Create information (like MAX_ROWS, ENGINE or
temporary table flag)
@param create_table [in] Pointer to TABLE_LIST object providing database
and name for table to be created or to be open
@param alter_info [in/out] Initial list of columns and indexes for the
table to be created
@param items [in] List of items which should be used to produce
rest of fields for the table (corresponding
fields will be added to the end of
alter_info->create_list)
@param lock [out] Pointer to the MYSQL_LOCK object for table
created will be returned in this parameter.
Since this table is not included in THD::lock
caller is responsible for explicitly unlocking
this table.
@param hooks [in] Hooks to be invoked before and after obtaining
table lock on the table being created.
NOTES
This function behaves differently for base and temporary tables:
- For base table we assume that either table exists and was pre-opened
and locked at open_and_lock_tables() stage (and in this case we just
emit error or warning and return pre-opened TABLE object) or special
placeholder was put in table cache that guarantees that this table
won't be created or opened until the placeholder will be removed
(so there is an exclusive lock on this table).
- We don't pre-open existing temporary table, instead we either open
or create and then open table in this function.
@note
This function assumes that either table exists and was pre-opened and
locked at open_and_lock_tables() stage (and in this case we just emit
error or warning and return pre-opened TABLE object) or an exclusive
metadata lock was acquired on table so we can safely create, open and
lock table in it (we don't acquire metadata lock if this create is
for temporary table).
@note
Since this function contains some logic specific to CREATE TABLE ...
SELECT it should be changed before it can be used in other contexts.
RETURN VALUES
non-zero Pointer to TABLE object for table created or opened
0 Error
@retval non-zero Pointer to TABLE object for table created or opened
@retval 0 Error
*/
static TABLE *create_table_from_items(THD *thd, HA_CREATE_INFO *create_info,
@ -3529,14 +3526,12 @@ static TABLE *create_table_from_items(THD *thd, HA_CREATE_INFO *create_info,
open_table().
*/
{
tmp_disable_binlog(thd);
if (!mysql_create_table_no_lock(thd, create_table->db,
create_table->table_name,
create_info, alter_info, 0,
select_field_count))
{
if (create_info->table_existed &&
!(create_info->options & HA_LEX_CREATE_TMP_TABLE))
if (create_info->table_existed)
{
/*
This means that someone created table underneath server
@ -3572,8 +3567,7 @@ static TABLE *create_table_from_items(THD *thd, HA_CREATE_INFO *create_info,
{
Open_table_context ot_ctx_unused(thd);
if (open_table(thd, create_table, thd->mem_root, &ot_ctx_unused,
MYSQL_OPEN_TEMPORARY_ONLY) &&
!create_info->table_existed)
MYSQL_OPEN_TEMPORARY_ONLY))
{
/*
This shouldn't happen as creation of temporary table should make
@ -3586,7 +3580,6 @@ static TABLE *create_table_from_items(THD *thd, HA_CREATE_INFO *create_info,
table= create_table->table;
}
}
reenable_binlog(thd);
if (!table) // open failed
DBUG_RETURN(0);
}
@ -3610,9 +3603,7 @@ static TABLE *create_table_from_items(THD *thd, HA_CREATE_INFO *create_info,
mysql_unlock_tables(thd, *lock);
*lock= 0;
}
if (!create_info->table_existed)
drop_open_table(thd, table, create_table->db, create_table->table_name);
drop_open_table(thd, table, create_table->db, create_table->table_name);
DBUG_RETURN(0);
}
DBUG_RETURN(table);
@ -3704,7 +3695,7 @@ select_create::prepare(List<Item> &values, SELECT_LEX_UNIT *u)
DBUG_EXECUTE_IF("sleep_create_select_before_check_if_exists", my_sleep(6000000););
if (!(create_info->options & HA_LEX_CREATE_TMP_TABLE) && create_table->table)
if (create_table->table)
{
/* Table already exists and was open at open_and_lock_tables() stage. */
if (create_info->options & HA_LEX_CREATE_IF_NOT_EXISTS)