The problem is that some DDL statements (ALTER TABLE, CREATE
TRIGGER, FLUSH TABLES, ...) when under LOCK TABLES need to
momentarily drop the lock, reopen the table and grab the write
lock again (using reopen_tables). When grabbing the lock again,
reopen_tables doesn't pass a flag to mysql_lock_tables in
order to ignore the impending global read lock, which causes a
assertion because LOCK_open is being hold. Also dropping the
lock must not signal to any threads that the table has been
relinquished (related to the locking/flushing protocol).
The solution is to correct the way the table is reopenned
and the locks grabbed. When reopening the table and under
LOCK TABLES, the table version should be set to 0 so other
threads have to wait for the table. When grabbing the lock,
any other flush should be ignored because it's theoretically
a atomic operation. The chosen solution also fixes a potential
discrepancy between binlog and GRL (global read lock) because
table placeholders were being ignored, now a FLUSH TABLES WITH
READ LOCK will properly for table with open placeholders.
It's also important to mention that this patch doesn't fix
a potential deadlock if one uses two GRLs under LOCK TABLES
concurrently.
cause ROLLBACK of statement", part 1. Review fixes.
Do not send OK/EOF packets to the client until we reached the end of
the current statement.
This is a consolidation, to keep the functionality that is shared by all
SQL statements in one place in the server.
Currently this functionality includes:
- close_thread_tables()
- log_slow_statement().
After this patch and the subsequent patch for Bug#12713, it shall also include:
- ha_autocommit_or_rollback()
- net_end_statement()
- query_cache_end_of_result().
In future it may also include:
- mysql_reset_thd_for_next_command().
The patch for Bug 26379 (Combination of FLUSH TABLE and
REPAIR TABLE corrupts a MERGE table) fixed this bug too.
However it revealed a new bug that crashed the server.
Flushing a merge table at the moment when it is between open
and attach of children crashed the server.
The flushing thread wants to abort locks on the flushed table.
It calls ha_myisammrg::lock_count() and ha_myisammrg::store_lock()
on the TABLE object of the other thread.
Changed ha_myisammrg::lock_count() and ha_myisammrg::store_lock()
to accept non-attached children. ha_myisammrg::lock_count() returns
the number of MyISAM tables in the MERGE table so that the memory
allocation done by get_lock_data() is done correctly, even if the
children become attached before ha_myisammrg::store_lock() is
called. ha_myisammrg::store_lock() will not return any lock if the
children are not attached.
This is however a change in the handler interface. lock_count()
can now return a higher number than store_lock() stores locks.
This is more safe than the reverse implementation would be.
get_lock_data() in the SQL layer is adjusted accordingly. It sets
MYSQL_LOCK::lock_count based on the number of locks returned by
the handler::store_lock() calls, not based on the numbers returned
by the handler::lock_count() calls. The latter are only used for
allocation of memory now.
No test case. The test suite cannot reliably run FLUSH between
lock_count() and store_lock() of another thread. The bug report
contains a program that can repeat the problem with some
probability.
This bug is actually two bugs in one, one of which is CREATE TRIGGER under
LOCK TABLES and the other is CREATE TRIGGER under LOCK TABLES simultaneous
to a FLUSH TABLES WITH READ LOCK (global read lock). Both situations could
lead to a server crash or deadlock.
The first problem arises from the fact that when under LOCK TABLES, if the
table is in the set of locked tables, the table is already open and it doesn't
need to be reopened (not a placeholder). Also in this case, if the table is
not write locked, a exclusive lock can't be acquired because of a possible
deadlock with another thread also holding a (read) lock on the table. The
second issue arises from the fact that one should never wait for a global
read lock if it's holding any locked tables, because the global read lock
is waiting for these tables and this leads to a circular wait deadlock.
The solution for the first case is to check if the table is write locked
and upgraded the write lock to a exclusive lock and fail otherwise for non
write locked tables. Grabbin the exclusive lock in this case also means
to ensure that the table is opened only by the calling thread. The second
issue is partly fixed by not waiting for the global read lock if the thread
is holding any locked tables.
The second issue is only partly addressed in this patch because it turned
out to be much wider and also affects other DDL statements. Reported as
Bug#32395
The problem is that DROP TABLE and other DDL statements failed to
automatically close handlers associated with tables that were marked
for reopen (FLUSH TABLES).
The current implementation fails to properly discard handlers of
dropped tables (that were marked for reopen) because it searches
on the open handler tables list and using the current alias of the
table being dropped. The problem is that it must not use the open
handler tables list to search because the table might have been
closed (marked for reopen) by a flush tables command and also it
must not use the current table alias at all since multiple different
aliases may be associated with a single table. This is specially
visible when a user has two open handlers (using alias) of a same
table and a flush tables command is issued before the table is
dropped (see test case). Scanning the handler table list is also
useless for dropping handlers associated with temporary tables,
because temporary tables are not kept in the THD::handler_tables
list.
The solution is to simple scan the handlers hash table searching
for, and deleting all handlers with matching table names if the
reopen flag is not passed to the flush function, indicating that
the handlers should be deleted. All matching handlers are deleted
even if the associated the table is not open.
When the server was out of memory it crashed because of invalid memory access.
This patch adds detection for failed memory allocations and make the server
output a proper error message.
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.
The columns in HAVING can reference the GROUP BY and
SELECT columns. There can be "table" prefixes when
referencing these columns. And these "table" prefixes
in HAVING use the table alias if available.
This means that table aliases are subject to the same
storage rules as table names and are dependent on
lower_case_table_names in the same way as the table
names are.
Fixed by :
1. Treating table aliases as table names
and make them lowercase when printing out the SQL
statement for view persistence.
2. Using case insensitive comparison for table
aliases when requested by lower_case_table_names
partitioned table
Trying INSERT DELAYED on a partitioned table, that has not been
used right before, crashes the server. When a table is used for
select or update, it is kept open for some time. This period I
mean with "right before".
Information about partitioning of a table is stored in form of
a string in the .frm file. Parsing of this string requires a
correctly set up lexical analyzer (lex). The partitioning code
uses a new temporary instance of a lex. But it does still refer
to the previously active lex. The delayd insert thread does not
initialize its lex though...
Added initialization for thd->lex before open table in the delayed
thread and at all other places where it is necessary to call
lex_start() if all tables would be partitioned and need to parse
the .frm file.
If a stored function that contains a drop temporary table statement
is invoked by a create temporary table of the same name may cause
a server crash. The problem is that when dropping a table no check
is done to ensure that table is not being used by some outer query
(or outer statement), potentially leaving the outer query with a
reference to a stale (freed) table.
The solution is when dropping a temporary table, always check if
the table is being used by some outer statement as a temporary
table can be dropped inside stored procedures.
The check is performed by looking at the TABLE::query_id value for
temporary tables. To simplify this check and to solve a bug related
to handling of temporary tables in prelocked mode, this patch changes
the way in which this member is used to track the fact that table is
used/unused. Now we ensure that TABLE::query_id is zero for unused
temporary tables (which means that all temporary tables which were
used by a statement should be marked as free for reuse after it's
execution has been completed).
and convert it to a warning instead of direct manipulation with the
thread error stack.
Fix a bug in handler::print_erorr when a garbled message was
printed for HA_ERR_NO_SUCH_TABLE.
This is a pre-requisite patch for the fix for Bug#12713 Error in a stored
function called from a SELECT doesn't cause ROLLBACK of statem
SHOW FIELDS FROM a view with no valid definer was possible (since fix
for Bug#26817), but gave NULL as a field-type. This led to mysqldump-ing
of such views being successful, but loading such a dump with the client
failing. Patch allows SHOW FIELDS to give data-type of field in underlying
table.
The root cause of this defect is that a call to my_error() is using a
'LEX_STRING' parameter instead of a 'char*'
This patch fixes the failing calls to my_error(), as well as similar calls
found during investigation.
This is a compiling bug (see the instrumentation in the bug report), no test cases provided.
The server crashed when a thread was killed while locking the
general_log table at statement begin.
The general_log table is handled like a performance schema table.
The state of open tables is saved and cleared so that this table
seems to be the only open one. Then this table is opened and locked.
After writing, the table is closed and the open table state is
restored. Before restoring, however, it is asserted that there is
no current table open.
After locking the table, mysql_lock_tables() checks if the thread
was killed in between. If so, it unlocks the table and returns an
error. open_ltable() just returns with the error and leaves closing
of the table to close_thread_tables(), which is called at
statement end.
open_performance_schema_table() did not take this into account.
It assumed that a failed open_ltable() would not leave an open
table behind.
Fixed by closing thread tables after open_ltable() and before
restore_backup_open_tables_state() if the thread was killed.
No test case. It requires correctly timed parallel execution.
Since this bug was detected by the test suite, it seems
dispensable to add another test.
This deadlock occurs when a client issues a HANDLER ... OPEN statement
that tries to open a table that has a pending name-lock on it by another
client that also needs a name-lock on some other table which is already
open and associated to a HANDLER instance owned by the first client.
The deadlock happens because the open_table() function will back-off
and wait until the name-lock goes away, causing a circular wait if some
other name-lock is also pending for one of the open HANDLER tables.
Such situation, for example, can be easily repeated by issuing a RENAME
TABLE command in such a way that the existing table is already open
as a HANDLER table by another client and this client tries to open
a HANDLER to the new table name.
The solution is to allow handler tables with older versions (marked for
flush) to be closed before waiting for the name-lock completion. This is
safe because no other name-lock can be issued between the flush and the
check for pending name-locks.
The test case for this bug is going to be committed into 5.1 because it
requires a test feature only avaiable in 5.1 (wait_condition).
When expanding a * in a USING/NATURAL join the check for table access
for both tables in the join was done using the grant information of the
first one.
Fixed by getting the grant information for the current table while
iterating through the columns of the join.
failures)
Fixed open_performance_schema_table() and close_performance_schema_table()
implementation and callers, to always execute balanced calls to:
thd->reset_n_backup_open_tables_state(backup);
thd->restore_backup_open_tables_state(backup);
This is a follow up for the patch for Bug#26162 "Trigger DML ignores low_priority_updates setting", where the stored procedure ignores the session setting of low_priority_updates.
This is a follow up for the patch for Bug#26162 "Trigger DML ignores low_priority_updates setting", where the stored procedure ignores the session setting of low_priority_updates.
For every table open operation with default write (TL_WRITE_DEFAULT) lock_type, downgrade the lock type to the session setting of low_priority_updates.
The bug caused memory corruption for some queries with top OR level
in the WHERE condition if they contained equality predicates and
other sargable predicates in disjunctive parts of the condition.
The corruption happened because the upper bound of the memory
allocated for KEY_FIELD and SARGABLE_PARAM internal structures
containing info about potential lookup keys was calculated incorrectly
in some cases. In particular it was calculated incorrectly when the
WHERE condition was an OR formula with disjuncts being AND formulas
including equalities and other sargable predicates.
Moved duplicated code to inline function store_timestamp()
Save thd->time_zone_used when logging to table as CSV internally cases it to be changed
Added MYSQL_LOCK_IGNORE_FLUSH to log tables to avoid deadlock in case of flush tables.
Mark log tables with TIMESTAMP_NO_AUTO_SET to avoid automatic timestamping
Set TABLE->no_replicate on open
between perm and temp tables. Review fixes.
The original bug report complains that if we locked a temporary table
with LOCK TABLES statement, we would not leave LOCK TABLES mode
when this temporary table is dropped.
Additionally, the bug was escalated when it was discovered than
when a temporary transactional table that was previously
locked with LOCK TABLES statement was dropped, futher actions with
this table, such as UNLOCK TABLES, would lead to a crash.
The problem originates from incomplete support of transactional temporary
tables. When we added calls to handler::store_lock()/handler::external_lock()
to operations that work with such tables, we only covered the normal
server code flow and did not cover LOCK TABLES mode.
In LOCK TABLES mode, ::external_lock(LOCK) would sometimes be called without
matching ::external_lock(UNLOCK), e.g. when a transactional temporary table
was dropped. Additionally, this table would be left in the list of LOCKed
TABLES.
The patch aims to address this inadequacy. Now, whenever an instance
of 'handler' is destroyed, we assert that it was priorly
external_lock(UNLOCK)-ed. All the places that violate this assert
were fixed.
This patch introduces no changes in behavior -- the discrepancy in
behavior will be fixed when we start calling ::store_lock()/::external_lock()
for all tables, regardless whether they are transactional or not,
temporary or not.
Bug#25422 (Hang with log tables)
Bug 17876 (Truncating mysql.slow_log in a SP after using cursor locks the
thread)
Bug 23044 (Warnings on flush of a log table)
Bug 29129 (Resetting general_log while the GLOBAL READ LOCK is set causes
a deadlock)
Prior to this fix, the server would hang when performing concurrent
ALTER TABLE or TRUNCATE TABLE statements against the LOG TABLES,
which are mysql.general_log and mysql.slow_log.
The root cause traces to the following code:
in sql_base.cc, open_table()
if (table->in_use != thd)
{
/* wait_for_condition will unlock LOCK_open for us */
wait_for_condition(thd, &LOCK_open, &COND_refresh);
}
The problem with this code is that the current implementation of the
LOGGER creates 'fake' THD objects, like
- Log_to_csv_event_handler::general_log_thd
- Log_to_csv_event_handler::slow_log_thd
which are not associated to a real thread running in the server,
so that waiting for these non-existing threads to release table locks
cause the dead lock.
In general, the design of Log_to_csv_event_handler does not fit into the
general architecture of the server, so that the concept of general_log_thd
and slow_log_thd has to be abandoned:
- this implementation does not work with table locking
- it will not work with commands like SHOW PROCESSLIST
- having the log tables always opened does not integrate well with DDL
operations / FLUSH TABLES / SET GLOBAL READ_ONLY
With this patch, the fundamental design of the LOGGER has been changed to:
- always open and close a log table when writing a log
- remove totally the usage of fake THD objects
- clarify how locking of log tables is implemented in general.
See WL#3984 for details related to the new locking design.
Additional changes (misc bugs exposed and fixed):
1)
mysqldump which would ignore some tables in dump_all_tables_in_db(),
but forget to ignore the same in dump_all_views_in_db().
2)
mysqldump would also issue an empty "LOCK TABLE" command when all the tables
to lock are to be ignored (numrows == 0), instead of not issuing the query.
3)
Internal errors handlers could intercept errors but not warnings
(see sql_error.cc).
4)
Implementing a nested call to open tables, for the performance schema tables,
exposed an existing bug in remove_table_from_cache(), which would perform:
in_use->some_tables_deleted=1;
against another thread, without any consideration about thread locking.
This call inside remove_table_from_cache() was not required anyway,
since calling mysql_lock_abort() takes care of aborting -- cleanly -- threads
that might hold a lock on a table.
This line (in_use->some_tables_deleted=1) has been removed.
by long running transaction
On Windows opened files can't be deleted. There was a special
upgraded lock mode (TL_WRITE instead of TL_WRITE_ALLOW_READ)
in ALTER TABLE to make sure nobody has the table opened
when deleting the old table in ALTER TABLE. This special mode
was causing ALTER TABLE to hang waiting on a lock inside InnoDB.
This special lock is no longer necessary as the server is
closing the tables it needs to delete in ALTER TABLE.
Fixed by removing the special lock.
Note that this also reverses the fix for bug 17264 that deals with
another consequence of this special lock mode being used.
The need arose when working on Bug 26141, where it became
necessary to replace TABLE_LIST with its forward declaration in a few
headers, and this involved a lot of s/TABLE_LIST/st_table_list/.
Although other workarounds exist, this patch is in line
with our general strategy of moving away from typedef-ed names.
Sometime in future we might also rename TABLE_LIST to follow the
coding style, but this is a huge change.
WL#3931 (Multi-table statement involving self-logging engines):
Adding logic to generate error if more than one engine is involved in
the statement and at least one engine is self-logging (i.e., has the
HA_HAS_OWN_BINLOGGING table flags set).
The log tables are by nature PERFORMANCE_SCHEMA tables,
which should not be affected by SET GLOBAL READ_ONLY or FLUSH TABLES
WITH READ LOCK.
The implementation of FLUSH TABLES WITH READ LOCK already ignored log tables.
Now with this patch, the implementation of LOCK TABLE also ignore a
global read lock for log tables, which was the missing symmetry.
replication):
Patch to add binlog format capabilities to the InnoDB storage engine.
The engine will not allow statement format logging when in READ COMMITTED
or READ UNCOMMITTED transaction isolation level.
In addition, an error is generated when trying to use READ COMMITTED
or READ UNCOMMITTED transaction isolation level in STATEMENT binlog
mode.
