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Bug#26379 - Combination of FLUSH TABLE and REPAIR TABLE

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corrupts a MERGE table
Bug 26867 - LOCK TABLES + REPAIR + merge table result in
            memory/cpu hogging
Bug 26377 - Deadlock with MERGE and FLUSH TABLE
Bug 25038 - Waiting TRUNCATE
Bug 25700 - merge base tables get corrupted by
            optimize/analyze/repair table
Bug 30275 - Merge tables: flush tables or unlock tables
            causes server to crash
Bug 19627 - temporary merge table locking
Bug 27660 - Falcon: merge table possible
Bug 30273 - merge tables: Can't lock file (errno: 155)

The problems were:

Bug 26379 - Combination of FLUSH TABLE and REPAIR TABLE
                corrupts a MERGE table

  1. A thread trying to lock a MERGE table performs busy waiting while
     REPAIR TABLE or a similar table administration task is ongoing on
     one or more of its MyISAM tables.
  
  2. A thread trying to lock a MERGE table performs busy waiting until all
     threads that did REPAIR TABLE or similar table administration tasks
     on one or more of its MyISAM tables in LOCK TABLES segments do UNLOCK
     TABLES. The difference against problem #1 is that the busy waiting
     takes place *after* the administration task. It is terminated by
     UNLOCK TABLES only.
  
  3. Two FLUSH TABLES within a LOCK TABLES segment can invalidate the
     lock. This does *not* require a MERGE table. The first FLUSH TABLES
     can be replaced by any statement that requires other threads to
     reopen the table. In 5.0 and 5.1 a single FLUSH TABLES can provoke
     the problem.

Bug 26867 - LOCK TABLES + REPAIR + merge table result in
            memory/cpu hogging

  Trying DML on a MERGE table, which has a child locked and
  repaired by another thread, made an infinite loop in the server.

Bug 26377 - Deadlock with MERGE and FLUSH TABLE

  Locking a MERGE table and its children in parent-child order
  and flushing the child deadlocked the server.

Bug 25038 - Waiting TRUNCATE

  Truncating a MERGE child, while the MERGE table was in use,
  let the truncate fail instead of waiting for the table to
  become free.

Bug 25700 - merge base tables get corrupted by
            optimize/analyze/repair table

  Repairing a child of an open MERGE table corrupted the child.
  It was necessary to FLUSH the child first.

Bug 30275 - Merge tables: flush tables or unlock tables
            causes server to crash

  Flushing and optimizing locked MERGE children crashed the server.

Bug 19627 - temporary merge table locking

  Use of a temporary MERGE table with non-temporary children
  could corrupt the children.

  Temporary tables are never locked. So we do now prohibit
  non-temporary chidlren of a temporary MERGE table.

Bug 27660 - Falcon: merge table possible

  It was possible to create a MERGE table with non-MyISAM children.

Bug 30273 - merge tables: Can't lock file (errno: 155)

  This was a Windows-only bug. Table administration statements
  sometimes failed with "Can't lock file (errno: 155)".

These bugs are fixed by a new implementation of MERGE table open.

When opening a MERGE table in open_tables() we do now add the
child tables to the list of tables to be opened by open_tables()
(the "query_list"). The children are not opened in the handler at
this stage.

After opening the parent, open_tables() opens each child from the
now extended query_list. When the last child is opened, we remove
the children from the query_list again and attach the children to
the parent. This behaves similar to the old open. However it does
not open the MyISAM tables directly, but grabs them from the already
open children.

When closing a MERGE table in close_thread_table() we detach the
children only. Closing of the children is done implicitly because
they are in thd->open_tables.

For more detail see the comment at the top of ha_myisammrg.cc.

Changed from open_ltable() to open_and_lock_tables() in all places
that can be relevant for MERGE tables. The latter can handle tables
added to the list on the fly. When open_ltable() was used in a loop
over a list of tables, the list must be temporarily terminated
after every table for open_and_lock_tables().
table_list->required_type is set to FRMTYPE_TABLE to avoid open of
special tables. Handling of derived tables is suppressed.
These details are handled by the new function
open_n_lock_single_table(), which has nearly the same signature as
open_ltable() and can replace it in most cases.

In reopen_tables() some of the tables open by a thread can be
closed and reopened. When a MERGE child is affected, the parent
must be closed and reopened too. Closing of the parent is forced
before the first child is closed. Reopen happens in the order of
thd->open_tables. MERGE parents do not attach their children
automatically at open. This is done after all tables are reopened.
So all children are open when attaching them.

Special lock handling like mysql_lock_abort() or mysql_lock_remove()
needs to be suppressed for MERGE children or forwarded to the parent.
This depends on the situation. In loops over all open tables one
suppresses child lock handling. When a single table is touched,
forwarding is done.

Behavioral changes:
===================

This patch changes the behavior of temporary MERGE tables.
Temporary MERGE must have temporary children.
The old behavior was wrong. A temporary table is not locked. Hence
even non-temporary children were not locked. See
Bug 19627 - temporary merge table locking.

You cannot change the union list of a non-temporary MERGE table
when LOCK TABLES is in effect. The following does *not* work:
CREATE TABLE m1 ... ENGINE=MRG_MYISAM ...;
LOCK TABLES t1 WRITE, t2 WRITE, m1 WRITE;
ALTER TABLE m1 ... UNION=(t1,t2) ...;
However, you can do this with a temporary MERGE table.

You cannot create a MERGE table with CREATE ... SELECT, neither
as a temporary MERGE table, nor as a non-temporary MERGE table.
CREATE TABLE m1 ... ENGINE=MRG_MYISAM ... SELECT ...;
Gives error message: table is not BASE TABLE.
This commit is contained in:
istruewing@stella.local
2007-11-15 20:25:43 +01:00
parent 2ecdc68e55
commit 0605274155
35 changed files with 4417 additions and 329 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
sql/mysql_priv.h
View File

@ -686,7 +686,6 @@ bool check_single_table_access(THD *thd, ulong privilege,
bool check_routine_access(THD *thd,ulong want_access,char *db,char *name,
bool is_proc, bool no_errors);
bool check_some_access(THD *thd, ulong want_access, TABLE_LIST *table);
bool check_merge_table_access(THD *thd, char *db, TABLE_LIST *table_list);
bool check_some_routine_access(THD *thd, const char *db, const char *name, bool is_proc);
bool multi_update_precheck(THD *thd, TABLE_LIST *tables);
bool multi_delete_precheck(THD *thd, TABLE_LIST *tables);
@ -1148,6 +1147,9 @@ TABLE *table_cache_insert_placeholder(THD *thd, const char *key,
bool lock_table_name_if_not_cached(THD *thd, const char *db,
const char *table_name, TABLE **table);
TABLE *find_locked_table(THD *thd, const char *db,const char *table_name);
void detach_merge_children(TABLE *table, bool clear_refs);
bool fix_merge_after_open(TABLE_LIST *old_child_list, TABLE_LIST **old_last,
TABLE_LIST *new_child_list, TABLE_LIST **new_last);
bool reopen_table(TABLE *table);
bool reopen_tables(THD *thd,bool get_locks,bool in_refresh);
void close_data_files_and_morph_locks(THD *thd, const char *db,
@ -1398,8 +1400,21 @@ int init_ftfuncs(THD *thd, SELECT_LEX* select, bool no_order);
void wait_for_condition(THD *thd, pthread_mutex_t *mutex,
pthread_cond_t *cond);
int open_tables(THD *thd, TABLE_LIST **tables, uint *counter, uint flags);
int simple_open_n_lock_tables(THD *thd,TABLE_LIST *tables);
bool open_and_lock_tables(THD *thd,TABLE_LIST *tables);
/* open_and_lock_tables with optional derived handling */
bool open_and_lock_tables_derived(THD *thd, TABLE_LIST *tables, bool derived);
/* simple open_and_lock_tables without derived handling */
inline bool simple_open_n_lock_tables(THD *thd, TABLE_LIST *tables)
{
return open_and_lock_tables_derived(thd, tables, FALSE);
}
/* open_and_lock_tables with derived handling */
inline bool open_and_lock_tables(THD *thd, TABLE_LIST *tables)
{
return open_and_lock_tables_derived(thd, tables, TRUE);
}
/* simple open_and_lock_tables without derived handling for single table */
TABLE *open_n_lock_single_table(THD *thd, TABLE_LIST *table_l,
thr_lock_type lock_type);
bool open_normal_and_derived_tables(THD *thd, TABLE_LIST *tables, uint flags);
int lock_tables(THD *thd, TABLE_LIST *tables, uint counter, bool *need_reopen);
int decide_logging_format(THD *thd, TABLE_LIST *tables);
@ -1976,7 +1991,8 @@ int format_number(uint inputflag,uint max_length,char * pos,uint length,
/* table.cc */
TABLE_SHARE *alloc_table_share(TABLE_LIST *table_list, char *key,
uint key_length);
void init_tmp_table_share(TABLE_SHARE *share, const char *key, uint key_length,
void init_tmp_table_share(THD *thd, TABLE_SHARE *share, const char *key,
uint key_length,
const char *table_name, const char *path);
void free_table_share(TABLE_SHARE *share);
int open_table_def(THD *thd, TABLE_SHARE *share, uint db_flags);