Both EXPLAIN and EXPLAIN EXTENDED statements produce different results set
in case it is run in normal way and in PS mode for the statements
UPDATE/DELETE with subquery.
The use case below reproduces the issue:
MariaDB [test]> CREATE TABLE t1 (c1 INT KEY) ENGINE=MyISAM;
Query OK, 0 rows affected (0,128 sec)
MariaDB [test]> CREATE TABLE t2 (c2 INT) ENGINE=MyISAM;
Query OK, 0 rows affected (0,023 sec)
MariaDB [test]> CREATE TABLE t3 (c3 INT) ENGINE=MyISAM;
Query OK, 0 rows affected (0,021 sec)
MariaDB [test]> EXPLAIN EXTENDED UPDATE t3 SET c3 =
-> ( SELECT COUNT(d1.c1) FROM ( SELECT a11.c1 FROM t1 AS a11
-> STRAIGHT_JOIN t2 AS a21 ON a21.c2 = a11.c1 JOIN t1 AS a12
-> ON a12.c1 = a11.c1 ) d1 );
+------+-------------+-------+------+---------------+------+---------+------+------+----------+--------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+------+-------------+-------+------+---------------+------+---------+------+------+----------+--------------------------------+
| 1 | PRIMARY | t3 | ALL | NULL | NULL | NULL | NULL | 0 | 100.00 | |
| 2 | SUBQUERY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Impossible WHERE noticed after reading const tables
+------+-------------+-------+------+---------------+------+---------+------+------+----------+--------------------------------+
2 rows in set (0,002 sec)
MariaDB [test]> PREPARE stmt FROM
-> EXPLAIN EXTENDED UPDATE t3 SET c3 =
-> ( SELECT COUNT(d1.c1) FROM ( SELECT a11.c1 FROM t1 AS a11
-> STRAIGHT_JOIN t2 AS a21 ON a21.c2 = a11.c1 JOIN t1 AS a12
-> ON a12.c1 = a11.c1 ) d1 );
Query OK, 0 rows affected (0,000 sec)
Statement prepared
MariaDB [test]> EXECUTE stmt;
+------+-------------+-------+------+---------------+------+---------+------+------+----------+--------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+------+-------------+-------+------+---------------+------+---------+------+------+----------+--------------------------------+
| 1 | PRIMARY | t3 | ALL | NULL | NULL | NULL | NULL | 0 | 100.00 | |
| 2 | SUBQUERY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | no matching row in const table |
+------+-------------+-------+------+---------------+------+---------+------+------+----------+--------------------------------+
2 rows in set (0,000 sec)
The reason by that different result sets are produced is that on execution
of the statement 'EXECUTE stmt' the flag SELECT_DESCRIBE not set
in the data member SELECT_LEX::options for instances of SELECT_LEX that
correspond to subqueries used in the UPDTAE/DELETE statements.
Initially, these flags were set on parsing the statement
PREPARE stmt FROM "EXPLAIN EXTENDED UPDATE t3 SET ..."
but latter they were reset before starting real execution of
the parsed query during handling the statement 'EXECUTE stmt';
So, to fix the issue the functions mysql_update()/mysql_delete()
have been modified to set the flag SELECT_DESCRIBE forcibly
in the data member SELECT_LEX::options for the primary SELECT_LEX
of the UPDATE/DELETE statement.
In the code existed just before this patch binding of a table reference to
the specification of the corresponding CTE happens in the function
open_and_process_table(). If the table reference is not the first in the
query the specification is cloned in the same way as the specification of
a view is cloned for any reference of the view. This works fine for
standalone queries, but does not work for stored procedures / functions
for the following reason.
When the first call of a stored procedure/ function SP is processed the
body of SP is parsed. When a query of SP is parsed the info on each
encountered table reference is put into a TABLE_LIST object linked into
a global chain associated with the query. When parsing of the query is
finished the basic info on the table references from this chain except
table references to derived tables and information schema tables is put
in one hash table associated with SP. When parsing of the body of SP is
finished this hash table is used to construct TABLE_LIST objects for all
table references mentioned in SP and link them into the list of such
objects passed to a pre-locking process that calls open_and_process_table()
for each table from the list.
When a TABLE_LIST for a view is encountered the view is opened and its
specification is parsed. For any table reference occurred in
the specification a new TABLE_LIST object is created to be included into
the list for pre-locking. After all objects in the pre-locking have been
looked through the tables mentioned in the list are locked. Note that the
objects referenced CTEs are just skipped here as it is impossible to
resolve these references without any info on the context where they occur.
Now the statements from the body of SP are executed one by one that.
At the very beginning of the execution of a query the tables used in the
query are opened and open_and_process_table() now is called for each table
reference mentioned in the list of TABLE_LIST objects associated with the
query that was built when the query was parsed.
For each table reference first the reference is checked against CTEs
definitions in whose scope it occurred. If such definition is found the
reference is considered resolved and if this is not the first reference
to the found CTE the the specification of the CTE is re-parsed and the
result of the parsing is added to the parsing tree of the query as a
sub-tree. If this sub-tree contains table references to other tables they
are added to the list of TABLE_LIST objects associated with the query in
order the referenced tables to be opened. When the procedure that opens
the tables comes to the TABLE_LIST object created for a non-first
reference to a CTE it discovers that the referenced table instance is not
locked and reports an error.
Thus processing non-first table references to a CTE similar to how
references to view are processed does not work for queries used in stored
procedures / functions. And the main problem is that the current
pre-locking mechanism employed for stored procedures / functions does not
allow to save the context in which a CTE reference occur. It's not trivial
to save the info about the context where a CTE reference occurs while the
resolution of the table reference cannot be done without this context and
consequentially the specification for the table reference cannot be
determined.
This patch solves the above problem by moving resolution of all CTE
references at the parsing stage. More exactly references to CTEs occurred in
a query are resolved right after parsing of the query has finished. After
resolution any CTE reference it is marked as a reference to to derived
table. So it is excluded from the hash table created for pre-locking used
base tables and view when the first call of a stored procedure / function
is processed.
This solution required recursive calls of the parser. The function
THD::sql_parser() has been added specifically for recursive invocations of
the parser.
XA transaction only allows to access data in specific states,
in ACTIVE, but not in IDLE or PREPARE.
But even then one should be able to run SHOW STATUS.
When you only need view structure, don't call handle_derived with
DT_CREATE and rely on its internal hackish check to skip DT_CREATE.
Because handle_derived is called from many different places,
and this internal hackish check is indiscriminative.
Instead, just don't ask handle_derived to do DT_CREATE
if you don't want it to do DT_CREATE.
Before this patch mergeable derived tables / view used in a multi-table
update / delete were merged before the preparation stage.
When the merge of a derived table / view is performed the on expression
attached to it is fixed and ANDed with the where condition of the select S
containing this derived table / view. It happens after the specification of
the derived table / view has been merged into S. If the ON expression refers
to a non existing field an error is reported and some other mergeable derived
tables / views remain unmerged. It's not a problem if the multi-table
update / delete statement is standalone. Yet if it is used in a stored
procedure the select with incompletely merged derived tables / views may
cause a problem for the second call of the procedure. This does not happen
for select queries using derived tables / views, because in this case their
specifications are merged after the preparation stage at which all ON
expressions are fixed.
This patch makes sure that merging of the derived tables / views used in a
multi-table update / delete statement is performed after the preparation
stage.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
The EXPLAIN EXTENDED statement run as a prepared statement can produce extra
warning comparing with a case when EXPLAIN EXTENDED statement is run as
a regular statement. For example, the following test case
CREATE TABLE t1 (c int);
CREATE TABLE t2 (d int);
EXPLAIN EXTENDED SELECT (SELECT 1 FROM t2 WHERE d = c) FROM t1;
produces the extra warning
"Field or reference 'c' of SELECT #2 was resolved in SELECT #1"
in case the above mentioned "EXPLAIN EXTENDED" statement is executed
in PS mode, that is by submitting the following statements:
PREPARE stmt FROM "EXPLAIN EXTENDED SELECT (SELECT 1 FROM t2 WHERE d = c) FROM t1";
EXECUTE stmt;
The reason of the extra warning emittion is in a way items
are handled (being fixed) during execution of the JOIN::prepare() method.
The method Item_field::fix_fields() calls the find_field_in_tables()
function in case a field hasn't been associated yet with the item.
Implementation of the find_field_in_tables() function first checks whether
a table containing the required field was already opened and cached.
It is done by checking the data member item->cached_table. This data member
is set on handling the PRERARE FROM statement and checked on executing
the EXECUTE statement. If the data member item->cached_table is set
the find_field_in_tables() function invoked and the
mark_select_range_as_dependent() function called if the field
is an outer referencee. The mark_select_range_as_dependent() function
calls the mark_as_dependent() function that finally invokes
the push_warning_printf() function that produces extra warning.
To fix the issue, calling of push_warning_printf() is elimited in case
it was run indirectly in result of hanlding already opened table from
the Item_field::fix_fields() method.
Problem:
=======
Upon deleting or updating a row in a parent table (with primary key), if
the child table has virtual column and an associated key with ON UPDATE
CASCADE/ON DELETE CASCADE, it will result in slave crash.
Analysis:
========
Tables which are related through foreign key require prelocking similar to
triggers. i.e If a table has triggers/foreign keys we should add all tables
and routines used by them to the prelocking set. This prelocking happens
during 'open_and_lock_tables' call. Each table being opened is checked for
foreign key references. If foreign key reference exists then the child
table is opened and it is linked to the table_list. Upon any modification
to parent table its corresponding child tables are retried from table_list
and they are updated accordingly. This prelocking work fine on master.
On slave prelocking works for following cases.
- Statement/mixed based replication
- In row based replication when trigger execution is enabled through
'slave_run_triggers_for_rbr=YES/LOGGING/ENFORCE'
Otherwise it results in an assert/crash, as the parent table will not find
the corresponding child table and it will be NULL. Dereferencing NULL
pointer leads to slave server exit.
Fix:
===
Introduce a new 'slave_fk_event_map' flag similar to 'trg_event_map'. This
flag will ensure that when foreign key is enabled in row based replication
all the parent and child tables are prelocked, so that parent is able to
locate the child table.
Note: This issue is specific to slave, hence only slave needs to be
upgraded.
When the query using a recursive CTE whose definition contained wildcard
symbols in the recursive part was processed at the prepare stage an
assertion was hit if the query was executed without any default database
set. The failure happened when the function insert_fields() tried to check
column privileges for the temporary table created for a recursive
reference to the CTE. No acl checks are needed for any CTE. That's why this
check should be blocked as well. The patch formulates a stricter condition
at which this check is to be blocked that covers the case when a query
using recursive CTEs is executed with no default database set.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
The reason for the failure is that
thd->mdl_context.release_transactional_locks()
was called after commit & rollback even in cases where the current
transaction is still active.
For 10.2, 10.3 and 10.4 the fix is simple:
- Replace all calls to thd->mdl_context.release_transactional_locks() with
thd->release_transactional_locks(). The thd function will only call
the mdl_context function if there are no active transactional locks.
In 10.6 we will better fix where we will change the return value for
some trans_xxx() functions to indicate if transaction did close the
transaction or not. This will avoid the need of the indirect call.
Other things:
- trans_xa_commit() and trans_xa_rollback() will automatically
call release_transactional_locks() if the transaction is closed.
- We can't do that for the other functions as the caller of many of these
are doing additional work (like close_thread_tables) before calling
release_transactional_locks().
- Added missing abort_result_set() and missing DBUG_RETURN in
select_create::send_eof()
- Fixed wrong indentation in injector::transaction::commit()
Deadlock is possible between applier thread and local committing thread with active FLUSH TABLE.
Applier thread should skip table share checks and locks when opening table.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>
* Allocate items on thd->mem_root while refixing vcol exprs
* Make vcol tree changes register and roll them back after the statement is executed.
Explanation:
Due to collation implementation specifics an Item tree could change while fixing.
The tricky thing here is to make it on a proper arena.
It's usually not a problem when a field is deterministic, however, makes a pain vice-versa, during allocation allocating.
A non-deterministic field should be refixed on each statement, since it depends on the environment state.
Changing the tree will be temporary and therefore it should be reverted after the statement execution.
When acquiring SNW/SNRW/X MDL lock DDL/admin statements may abort pending
thr lock in concurrent connection with open HANDLER (or delayed insert
thread).
This may lead to a race condition when table->alias is accessed
concurrently by such threads. Either assertion failure or memory leak
is a practical consequence of this race condition.
Specifically HANDLER is opening a table and issuing alias.copy(), while
DDL executing get_lock_data()/alias.c_ptr()/realloc()/realloc_raw().
Fixed by perforimg table->init() before it is published via
thd->open_tables.
MDEV-21398 Deadlock (server hang) or assertion failure in
Diagnostics_area::set_error_status upon ALTER under lock
This failure could only happen if one locked the same table
multiple times and then did an ALTER TABLE on the table.
Major change is to change all instances of
table->m_needs_reopen= true;
to
table->mark_table_for_reopen();
The main fix for the problem was to ensure that we mark all
instances of the table in the locked_table_list and when we
reopen the tables, we first close all tables before reopening
and locking them.
Other things:
- Don't call thd->locked_tables_list.reopen_tables if there
are no tables marked for reopen. (performance)
The code erroneously allowed both:
INSERT INTO t1 (vcol) VALUES (DEFAULT);
INSERT INTO t1 (vcol) VALUES (DEFAULT(non_virtual_column));
The former is OK, but the latter is not.
Adding a new virtual method in Item:
virtual bool vcol_assignment_allowed_value() const { return false; }
Item_null, Item_param and Item_default_value override it.
Item_default_value overrides it in the way to:
- allow DEFAULT
- disallow DEFAULT(col)
This is a backport of the applicable part of
commit 93475aff8d and
commit 2c39f69d34
from 10.4.
Before 10.4 and Galera 4, WSREP_ON is a macro that points to
a global Boolean variable, so it is not that expensive to
evaluate, but we will add an unlikely() hint around it.
WSREP_ON_NEW: Remove. This macro was introduced in
commit c863159c32
when reverting WSREP_ON to its previous definition.
We replace some use of WSREP_ON with WSREP(thd), like it was done
in 93475aff8d. Note: the macro
WSREP() in 10.1 is equivalent to WSREP_NNULL() in 10.4.
Item_func_rand::seed_random(): Avoid invoking current_thd
when WSREP is not enabled.
Problem was in a combination of LOCK TABLES on several Aria
tables followed by an ALTER TABLE. After the ALTER TABLE there
was a force close + reopen of the alter table. The close failed
because the table was still part of a transaction.
Fixed by calling extra(HA_EXTRA_PREPARE_FOR_FORCED_CLOSE) as
part of closing the table, which ensures that the table is not
anymore part of the current transaction.
remove a special treatment of a bare DEFAULT keyword that made it
behave inconsistently and differently from DEFAULT(column).
Now all forms of the explicit assignment of a default column value
behave identically, and all count as an explicitly assigned value
(for the purpose of ON UPDATE NOW).
followup for c7c481f4d9
Three issues here:
* ON UPDATE DEFAULT NOW columns were updated after generated columns
were computed - this broke indexed virtual columns
* ON UPDATE DEFAULT NOW columns were updated after BEFORE triggers,
so triggers didn't see the correct NEW value
* in case of a multi-update generated columns were also updated
after BEFORE triggers
* remove one level of virtual functions
* remove redundant checks
* remove an if() as the value is always known at compilation time
don't pretend that "DEFAULT expr" and "ON UPDATE DEFAULT NOW"
are "basically the same thing"
MDEV-17717
Assertion `!table->pos_in_locked_tables' failed in tc_release_table on
flushing RocksDB table under SERIALIZABLE
MDEV-17998
Deadlock and eventual Assertion `!table->pos_in_locked_tables' failed
in tc_release_table on KILL_TIMEOUT
MDEV-19591
Assertion `!table->pos_in_locked_tables' failed in tc_release_table upon
altering table into S3 under lock.
The problem was that thd->open_tables->pos_in_locked_tables was not reset
when alter table failed to reopen a locked table.
MDEV-5589 commit set up a policy to skip DROP TEMPORARY TABLE binary logging
in case the target table has not been "CREATEed" in binlog (no CREATE
Query-log-event was logged into the binary log).
It turns out that
1. the rule did not cover non-existing table DROPped with IF-EXISTS clause.
The logged-create knowledge for the non-existing one does not even need
MDEV-5589 patch, and
2. connection close disobeys it to trigger automatic DROP-IF-EXISTS
binlogging.
Either 1 or 2 or even both is/are also responsible for unexpected binlog
records observed in MDEV-17863, actually rendering a referred
@@global.read_only irrelevant as far as the described stored procedure
definition *and* the ROW binlog-format are concerned.
cmake -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_BUILD_TYPE=Debug
Maintainer mode makes all warnings errors. This patch fix warnings. Mostly about
deprecated `register` keyword.
Too much warnings came from Mroonga and I gave up on it.
as well as
MDEV-19500 Update with join stopped worked if there is a call to a procedure in a trigger
MDEV-19521 Update Table Fails with Trigger and Stored Function
MDEV-19497 Replication stops because table not found
MDEV-19527 UPDATE + JOIN + TRIGGERS = table doesn't exists error
Reimplement the fix for (5d510fdbf0)
MDEV-18507 can't update temporary table when joined with table with triggers on read-only
instead of calling open_tables() twice, put multi-update
prepare code inside open_tables() loop.
Add a test for a MDL backoff-and-retry loop inside open_tables()
across multi-update prepare code.
The bug was that when using mysql_list_fields, then
table_list->schema_table_name was not filled in.
Fixed by using table_list->schema_table instead, which is always
filled in.
Problem:
========
We have a Master/Master Setup on two servers, but are only writing to one of
those servers (so it is essentially Master/Slave) We upgraded from 10.1.* to
10.2.22 last week and starting with the upgrade, we are getting duplicate key
errors on the slave. BINLOG=mixed.
Analysis:
=========
This issue happens with LOCK TABLES and binlog_format=MIXED combination. When an
UNSAFE statement is encountered in 'MIXED' mode, it is logged in the form of
'ROW' format. For all the tables that are part of LOCK TABLES list their table maps
are written into the binary log. For each table in the list a check is
done to see if 'check_table_binlog_row_based_done' flag is set or not. If it is not set
a check process is initiated to see if table qualifies for row based binary
logging or not and 'check_table_binlog_row_based_done' is set. This flag will be
cleared at the time of closing thread tables.
But there can be special cases where the LOCK TABLES contains more number of
tables but the unsafe query is actually using subset of tables from LOCK TABLES
list.
For example: LOCK TABLES locks t1,t2,t3 but the unsafe statement makes use of
only two tables t1,t3. In this case the 'check_table_binlog_row_based_done' flag
is enabled for table 't2' while writing table map, but 'close_thread_tables'
function call will not reset this flag. Since the flag is not cleared for table
't2' even a safe statement which used t2 will be logged in the form of row based
format.
This leads to an assert on debug builds and causes duplicate entries in release
builds. In release builds a statement is logged in the form of both ROW and
STATEMENT format. This causes the slave to fail with duplicate key error.
Fix:
===
During 'close_thread_tables' when LOCK TABLE modes are active "ha_reset" is done
for all the tables which were part of current statement. As mentioned in the
example 'ha_reset' is called for tables 't1' and 't3'. This will clear the
'check_table_binlog_row_based_done' flag. At this point add a check for the rest
of the tables to see if 'check_table_binlog_row_based_done' is enabled or not.
If enabled clear the flag.
triggers are opened and tables used in triggers are prelocked in
open_tables(). But multi-update can detect what tables will actually
be updated only later, after all main tables are opened.
Meaning, if a table is used in multi-update, but is not actually updated,
its on-update treggers will be opened and tables will be prelocked,
even if it's unnecessary. This can cause more tables to be
write-locked than needed, causing read_only errors, privilege errors
and lock waits.
Fix: don't open/prelock triggers unless table->updating is true.
In multi-update after setting table->updating=true, do a second
open_tables() for newly added tables, if any.
