On shutdown feedback was sending a short report without creating
a THD. At that point current_thd was pointing to the already
destroyed THD from the previous full report.
backport from 10.1:
commit bfe703a
Author: Sergei Golubchik <serg@mariadb.org>
Date: Tue Feb 3 18:19:56 2015 +0100
don't let current_thd to point to a destroyed THD
Problem & Analysis: If DML invokes a trigger or a
stored function that inserts into an AUTO_INCREMENT column,
that DML has to be marked as 'unsafe' statement. If the
tables are locked in the transaction prior to DML statement
(using LOCK TABLES), then the same statement is not marked as
'unsafe' statement. The logic of checking whether unsafeness
is protected with if (!thd->locked_tables_mode). Hence if
we lock the tables prior to DML statement, it is *not* entering
into this if condition. Hence the statement is not marked
as unsafe statement.
Fix: Irrespective of locked_tables_mode value, the unsafeness
check should be done. Now with this patch, the code is moved
out to 'decide_logging_format()' function where all these checks
are happening and also with out 'if(!thd->locked_tables_mode)'.
Along with the specified test case in the bug scenario
(BINLOG_STMT_UNSAFE_AUTOINC_COLUMNS), we also identified that
other cases BINLOG_STMT_UNSAFE_AUTOINC_NOT_FIRST,
BINLOG_STMT_UNSAFE_WRITE_AUTOINC_SELECT, BINLOG_STMT_UNSAFE_INSERT_TWO_KEYS
are also protected with thd->locked_tables_mode which is not right. All
of those checks also moved to 'decide_logging_format()' function.
HA_MYISAMMRG.CC:631
Analysis
========
Any attempt to open a temporary MyISAM merge table consisting
of a view in its list of tables (not the last table in the list)
under LOCK TABLES causes the server to exit.
Current implementation doesn't perform sanity checks during
merge table creation. This allows merge table to be created
with incompatible tables (table with non-myisam engine),
views or even with table doesn't exist in the system.
During view open, check to verify whether requested view
is part of a merge table is missing under LOCK TABLES path
in open_table(). This leads to opening of underlying table
with parent_l having NULL value. Later when attaching child
tables to parent, this hits an ASSERT as all child tables
should have parent_l pointing to merge parent. If the operation
does not happen under LOCK TABLES mode, open_table() checks
for view's parent_l and returns error.
Fix:
======
Check added before opening view Under LOCK TABLES in open_table()
to verify whether it is part of merge table. Error is returned
if the view is part of a merge table.
find_item_in_list() now recognize view fields like a fields even if they rever to an expression.
The problem of schema name do not taken into account for field with it and
derived table fixed.
Duplicating code removed
Problem: Not all permanent Item_direct_view_ref was in permanent list of used items of the view.
Solution: Detect creating permenent view/derived table reference and put them in the permanent list at once.
In galera cluster, when myisam replication is enabled
(wsrep_replicate_myisam=ON), DML statements are replicated
in open_tables(). However, in case of prepared statements,
for an INSERT, open_tables() gets invoked twice. Once for
COM_STMT_PREPARE (to validate and prepare INSERT) and later
for COM_STMT_EXECUTE. As a result, the command gets replicated
twice. Same happens for REPLACE, UPDATE and DELETE commands.
Fixed by adding a check to not replicate during 'prepare'
phase. Also changed the order of conditions to make it more
efficient. Lastly, in order to support wsrep_dirty_reads, made
changes to allow COM_STMT_XXX commands to continue past initial
check even when wsrep is not ready.
Alternative fix that doesn't cause view.test crash in --ps:
Remember when Item_ref was fixed right in the constructor
and did not have a full Item_ref::fix_fields() call. Later
in PS/SP, after Item_ref::cleanup, we use this knowledge
to avoid doing full fix_fields() for items that were never
supposed to be fix_field'ed.
Simplify the test case.
SELECT ... WHERE XX IN (SELECT YY)
this was transformed to something like:
SELECT ... WHERE IF_EXISTS(SELECT ... HAVING XX=YY)
The bug was that for normal execution XX was fixed in the original outer SELECT context while in PS it was fixed in the sub query context and this confused the optimizer.
Fixed by ensuring that XX is always fixed in the outer context.
AVOID DEADLOCK AFTER RESTORE
Analysis
--------
Accessing the restored NDB table in an active multi-statement
transaction was resulting in deadlock found error.
MySQL Server needs to discover metadata of NDB table from
data nodes after table is restored from backup. Metadata
discovery happens on the first access to restored table.
Current code mandates this statement to be the first one
in the transaction. This is because discover needs exclusive
metadata lock on the table. Lock upgrade at this point can
lead to MDL deadlock and the code was written at the time
when MDL deadlock detector was not present. In case when
discovery attempted in the statement other than the first
one in transaction ER_LOCK_DEADLOCK error is reported
pessimistically.
Fix:
---
Removed the constraint as any potential deadlock will be
handled by deadlock detector. Also changed code in discover
to keep metadata locks of active transaction.
Same issue was present in table auto repair scenario. Same
fix is added in repair path also.
This was a regression from the patch for MDEV-7668.
A test was incorrect, so the slave would not properly handle re-using
temporary tables, which lead to replication failure in this case.
It is possible for Item_field to have a NULL field_name. This is true if
the Item_field is created based on a field in a temporary table that has
no name. It is thus necessary to do a null check before attempting a
strcmp.
Make sure that in parallel replication, we execute wait_for_prior_commit()
before setting table->in_use for a temporary table. Otherwise we can end up
with two parallel replication worker threads competing with each other for
use of a temporary table.
Re-factor the use of find_temporary_table() to be able to handle errors
in the caller (as wait_for_prior_commit() can return error in case of
deadlock kill).
[This commit cherry-picked to be able to merge MDEV-7936, of which it
is a pre-requisite, into both 10.0 and 10.1.]
Parallel replication depends on locking (table locks, row locks, etc.) to
prevent two conflicting transactions from running and committing in parallel.
But temporary tables are designed to be visible only to one thread, and have
no such locking.
In the concrete issue, an intermediate master could commit a CREATE TEMPORARY
TABLE in the same group commit as in INSERT into that table. Thus, a
lower-level master could attempt to run them in parallel and get an error.
More generally, we need protection from parallel replication trying to run
transactions in parallel that access a common temporary table.
This patch simply causes use of a temporary table from parallel replication
to wait for all previous transactions to commit, serialising the replication
at that point.
(A more fine-grained locking could be added later, possibly. However,
using temporary tables in statement-based replication is in any case
normally undesirable; for example a restart of the server will lose
temporary tables and can break replication).
Note that row-based replication is not affected, as it does not do any
temporary tables on the slave-side.
This patch also cleans up the locking around protecting the list of
temporary tables in Relay_log_info. This used to take the
rli->data_lock at the end of every statement, which is very bad for
concurrency. With this patch, the lock is not taken unless temporary
tables (with statement-based binlogging) are in use on the slave.
Parallel replication depends on locking (table locks, row locks, etc.) to
prevent two conflicting transactions from running and committing in parallel.
But temporary tables are designed to be visible only to one thread, and have
no such locking.
In the concrete issue, an intermediate master could commit a CREATE TEMPORARY
TABLE in the same group commit as in INSERT into that table. Thus, a
lower-level master could attempt to run them in parallel and get an error.
More generally, we need protection from parallel replication trying to run
transactions in parallel that access a common temporary table.
This patch simply causes use of a temporary table from parallel replication
to wait for all previous transactions to commit, serialising the replication
at that point.
(A more fine-grained locking could be added later, possibly. However,
using temporary tables in statement-based replication is in any case
normally undesirable; for example a restart of the server will lose
temporary tables and can break replication).
Note that row-based replication is not affected, as it does not do any
temporary tables on the slave-side.
This patch also cleans up the locking around protecting the list of
temporary tables in Relay_log_info. This used to take the
rli->data_lock at the end of every statement, which is very bad for
concurrency. With this patch, the lock is not taken unless temporary
tables (with statement-based binlogging) are in use on the slave.
Do not use merge_for_insert for commands which use SELECT because optimizer can't work with such tables.
Fixes which makes multi-delete working with normally merged views.
