The test cases for the MDEV found several independent bugs
in MariaDB server and Aria:
- If a temporary table was marked as crashed, it could never
be deleted.
- Opening of a crashed temporary table gave an error message
but the error was never forwarded to the caller which caused
an assert() in my_ok()
- init_read_record() did mmap of all temporary tables, which is
probably not a good idea as this area can potentially be
very big. Changed code to only mmap internal temporary tables.
- mmap-ed tables where not unmapped in case of repair/optimize
which caused bad data in table and crashes if the original
table files where replaced with new ones (as the old mmap
was still in place). Fixed by removing the mmap in case
of repair.
- Cleaned up usage of code that disabled mmap in Aria
Problem:
========
The test now fails with the following trace:
CURRENT_TEST: rpl.rpl_parallel_temptable
--- /mariadb/10.4/mysql-test/suite/rpl/r/rpl_parallel_temptable.result
+++ /mariadb/10.4/mysql-test/suite/rpl/r/rpl_parallel_temptable.reject
@@ -194,7 +194,6 @@
30 conservative
31 conservative
32 optimistic
-33 optimistic
Analysis:
=========
The part of test which fails with result content mismatch is given below.
CREATE TEMPORARY TABLE t4 (a INT PRIMARY KEY) ENGINE=InnoDB;
INSERT INTO t4 VALUES (32);
INSERT INTO t4 VALUES (33);
INSERT INTO t1 SELECT a, "optimistic" FROM t4;
slave_parallel_mode=optimistic
The expectation of the above test script is, INSERT FROM SELECT should read both
32, 33 and populate table 't1'. But this expectation fails occasionally.
All three INSERT statements are handed over to three different slave parallel
workers. Temporary tables are not safe for parallel replication. They were
designed to be visible to one thread only, so have no table locking. Thus there
is no protection against two conflicting transactions committing in parallel and
things like that.
So anything that uses temporary tables will be serialized with anything before
it, when using parallel replication by using a "wait_for_prior_commit" function
call. This will ensure that the each transaction is executed sequentially.
But there exists a code path in which the above wait doesn't happen. Because of
this at times INSERT from SELECT doesn't wait for the INSERT (33) to complete
and it completes its executes and enters commit stage. Hence only row 32 is
found in those cases resulting in test failure.
The wait needs to be added within "open_temporary_table" call. The code looks
like this within "open_temporary_table".
Each thread tries to open temporary table in 3 different ways:
case 1: Find a temporary table which is already in use by using
find_temporary_table(tl) && wait_for_prior_commit()
case 2: If above failed then try to look for temporary table which is marked for
free for reuse. This internally calls "wait_for_prior_commit()" if table
is found.
find_and_use_tmp_table(tl, &table)
case 3: If none of the above open a new table handle from table share.
if (!table && (share= find_tmp_table_share(tl)))
{ table= open_temporary_table(share, tl->get_table_name(), true); }
At present the "wait_for_prior_commit" happens only in case 1 & 2.
Fix:
====
On slave add a call for "wait_for_prior_commit" for case 3.
The above wait on slave will solve the issue. A more detailed fix would be to
mark temporary tables as not safe for parallel execution on the master side.
In order to do that, on the master side, mark the Gtid_log_event specific flag
FL_TRANSACTIONAL to be false all the time. So that they are not scheduled
parallely.
truncating a temporary table
TRUNCATE expects only one TABLE instance (which is used by TRUNCATE
itself) to be open. However this requirement wasn't enforced after
"MDEV-5535: Cannot reopen temporary table".
Fixed by closing unused table instances before performing TRUNCATE.
This was caused by a combination of factors:
* MyISAM/Aria temporary tables historically never saved the state
to disk (MYI/MAI), because the state never needed to persist
* certain ALTER TABLE operations modify the original TABLE structure
and if they fail, the original table has to be reopened to
revert all changes (m_needs_reopen=1)
as a result, when ALTER fails and MyISAM/Aria temp table gets reopened,
it reads the stale state from the disk.
As a fix, MyISAM/Aria tables now *always* write the state to disk
on close, *unless* HA_EXTRA_PREPARE_FOR_DROP was done first. And
the server now always does HA_EXTRA_PREPARE_FOR_DROP before dropping
a temporary table.
THD::close_temporary_tables(): Revert the change.
ha_innobase::delete_table(): Move the work-around inside
a debug assertion, and check thd_kill_level() instead of thd_killed(),
because the latter would not hold for KILL_CONNECTION.
THD::close_temporary_tables(): Assign lex->sql_command so that
the debug assertion will not fail in ha_innobase::delete_table().
Alternatively, we could ensure that thd_killed() holds inside
ha_innobase::delete_table().
There should be no impact for the non-debug build. The thd_sql_command()
inside ha_innobase::delete_table() only affects the treatment of
persistent FOREIGN KEY metadata. There is no persistent metadata
nor foreign key constraints for temporary tables.
No test case was added, because the failure is nondeterministic.
- Fix win64 pointer truncation warnings
(usually coming from misusing 0x%lx and long cast in DBUG)
- Also fix printf-format warnings
Make the above mentioned warnings fatal.
- fix pthread_join on Windows to set return value.
Temporary table being created by outer statement
should not be visible to inner statement. And if
inner statement creates a table with same name.
The whole statement should fail with
ER_TABLE_EXISTS_ERROR.
Implemented by temporarily de-linking the TABLE_SHARE
being created by outer statement so that it remains
hidden to the inner statement.
mysqld maintains a list of TABLE objects for all temporary
tables created within a session in THD. Here each table is
represented by a TABLE object.
A query referencing a particular temporary table for more
than once, however, failed with ER_CANT_REOPEN_TABLE error
because a TABLE_SHARE was allocate together with the TABLE,
so temporary tables always had only one TABLE per TABLE_SHARE.
This patch lift this restriction by separating TABLE and
TABLE_SHARE objects and storing TABLE_SHAREs for temporary
tables in a list in THD, and TABLEs in a list within their
respective TABLE_SHAREs.
