The problem was that "group_min_max optimization" does not work if
some aggregate functions, like COUNT(*), is used.
The function get_best_group_min_max() is using the join->sum_funcs
array to check which aggregate functions are used.
The bug was that aggregates in HAVING where not yet added to
join->sum_funcs at the time get_best_group_min_max() was called.
Fixed by populate join->sum_funcs already in prepare, which means that
all sum functions will be in join->sum_funcs in get_best_group_min_max().
A benefit of this approach is that we can remove several calls to
make_sum_func_list() from the code and simplify the function.
I removed some wrong setting of 'sort_and_group'.
This variable is set when alloc_group_fields() is called, as part
of allocating the cache needed by end_send_group() and does not need
to be set by other functions.
One problematic thing was that Spider is using *join->sum_funcs to detect
at which stage the optimizer is and do internal calculations of aggregate
functions. Updating join->sum_funcs early caused Spider to fail when trying
to find min/max values in opt_sum_query().
Fixed by temporarily resetting sum_funcs during opt_sum_query().
Reviewer: Sergei Petrunia
This bug may affect the queries that uses a grouping derived table with
grouping list containing references to columns from different tables if
the optimizer decides to employ the split optimization for the derived
table. In some very specific cases it may affect queries with a grouping
derived table that refers only one base table.
This bug was caused by an improper fix for the bug MDEV-25128. The fix
tried to get rid of the equality conditions pushed into the where clause
of the grouping derived table T to which the split optimization had been
applied. The fix erroneously assumed that only those pushed equalities
that were used for ref access of the tables referenced by T were needed.
In fact the function remove_const() that figures out what columns from the
group list can be removed if the split optimization is applied can uses
other pushed equalities as well.
This patch actually provides a proper fix for MDEV-25128. Rather than
trying to remove invalid pushed equalities referencing the fields of SJM
tables with a look-up access the patch attempts not to push such equalities.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
The 10.5 version of the patch.
Removing DEFAULT from INFORMATION_SCHEMA columns.
DEFAULT in read-only tables is rather meaningless.
Upgrade should go smoothly.
Also fixes:
MDEV-20254 Problems with EMPTY_STRING_IS_NULL and I_S tables
Removing DEFAULT from INFORMATION_SCHEMA columns.
DEFAULT in read-only tables is rather meaningless.
Upgrade should go smoothly.
Also fixes:
MDEV-20254 Problems with EMPTY_STRING_IS_NULL and I_S tables
The problem affected queries in form:
SELECT FROM (SELECT where Split Materialized is applicable) WHERE 1=0
The problem was caused by this:
- The select in derived table uses two-phase optimization (due to a
possible Split Materialized).
- The primary select has "Impossible where" and so it short-cuts its
optimization.
- The optimization for the SELECT in the derived table is never finished,
and EXPLAIN data structure has a dangling pointer to select #2.
Fixed with this: make JOIN::optimize_stage2() invoke optimization of
derived tables when it is handing a degenerate JOIN with zero tables.
We will not execute the derived tables but we need their query plans
for [SHOW]EXPLAIN.
Running a query using cursor could lead to a server crash on
building a temporary table used for handling the query.
For example, the following cursor
DECLARE cur1 CURSOR FOR
SELECT t2.c1 AS c1 FROM t1 LEFT JOIN t2 ON t1.c1 = t2.c1
WHERE EXISTS (SELECT 1 FROM t1 WHERE c2 = -1) ORDER BY c1;
declared and executed inside a stored routine could result in server
crash on creating a temporary table used for handling the ORDER BY clause.
Crash occurred on attempt to create the temporary table's fields based
on fields whose data located in a memory root that already freed.
It happens inside the function return_zero_rows() where the method
Select_materialize::send_result_set_metadata() is invoked for cursor case.
This method calls the st_select_lex_unit::get_column_types() in order to
get a list of items with types of columns for the temporary table being created.
The method st_select_lex_unit::get_column_types() returns
first_select()->join->fields
in case it is invoked for a cursor. Unfortunately, this memory has been already
deallocated bit earlier by calling
join->join_free();
inside the function return_zero_rows().
In case the query listed in the example is run in conventional way (without
using cursor) the method st_select_lex_unit::get_column_types()
returns first_select()->item_list that is not touched by invocation
of the method join->join_free() so everything is fine for that.
So, to fix the issue the resources allocated for the JOIN class should be
released after any activities with the JOIN class has been completed,
that is as the last statement before returning from the function
return_zero_rows().
This patch includes tests both for the case when a cursor is run explicitly
from within a stored routine and for the case when a cursor is opened
implicitly as prescribed by the STMT_ATTR_CURSOR_TYPE attribute of
binary protocol (the case of prepared statement).
The Spider storage engine ignored the implicit grouping when
aggregation was converted to constant by the query optimizer.
As a result, the Spider SE returned rows more than expected.
To fix the problem, we notify the Spider SE of the existence of
the implicit grouping via Query::distinct.
table: rows are counted twice
Analysis: When the table we are trying to insert into and the SELECT table
are same for INSERT ... SELECT, rows from the SELECT table are copied into
internal temporary table and then to the INSERT table. We only want to
count the rows when we start inserting into the table.
Fix: Reset the counter to 1 before starting to copy from internal temporary
table to select table and then increment the counter.
make_join_select() calls const_cond->val_int(). There are edge cases
where const_cond may have a not-yet optimized subquery.
(The subquery will have used_tables() covered by join->const_tables. It
will still have const_item()==false, so other parts of the optimizer
will not try to evaluate it. We should probably mark such subqueries
as constant but that is outside the scope of this MDEV)
Consider the following use case:
MariaDB [test]> CREATE TABLE t1 (field1 BIGINT DEFAULT -1);
MariaDB [test]> CREATE VIEW v1 AS SELECT DISTINCT field1 FROM t1;
Repeated execution of the following query as a Prepared Statement
MariaDB [test]> PREPARE stmt FROM 'SELECT * FROM v1 WHERE field1 <=> NULL';
MariaDB [test]> EXECUTE stmt;
results in a crash for a server built with DEBUG.
MariaDB [test]> EXECUTE stmt;
ERROR 2013 (HY000): Lost connection to MySQL server during query
Assertion failed: (!result), function convert_const_to_int, file item_cmpfunc.cc, line 476.
Abort trap: 6 (core dumped)
The crash inside the function convert_const_to_int() happens by the reason
that the value -1 is stored in an instance of the class Field_longlong
on restoring its original value in the statement
result= field->store(orig_field_val, TRUE);
that leads to assigning the value 1 to the variable 'result' with subsequent
crash in the DBUG_ASSERT statement following it
DBUG_ASSERT(!result);
The main matter here is why this assertion failure happens on the second
execution of the prepared statement and doens't on the first one.
On first handling of the statement
'EXECUTE stmt;'
a temporary table is created for serving the query involving the view 'v1'.
The table is created by the function create_tmp_table() in the following
calls trace: (trace #1)
JOIN::prepare (at sql_select.cc:725)
st_select_lex::handle_derived
LEX::handle_list_of_derived
TABLE_LIST::handle_derived
mysql_handle_single_derived
mysql_derived_prepare
select_union::create_result_table
create_tmp_table
Note, that the data member TABLE::status of a TABLE instance returned by the
function create_tmp_table() has the value 0.
Later the function setup_table_map() is called on the TABLE instance just
created for the sake of the temporary table (calls trace #2 is below):
JOIN::prepare (at sql_select.cc:737)
setup_tables_and_check_access
setup_tables
setup_table_map
where the data member TABLE::status is set to the value STATUS_NO_RECORD.
After that when execution of the method JOIN::prepare reaches calling of
the function setup_without_group() the following calls trace is invoked
JOIN::prepare
setup_without_group
setup_conds
Item_func::fix_fields
Item_func_equal::fix_length_and_dec
Item_bool_rowready_func2::fix_length_and_dec
Item_func::setup_args_and_comparator
Item_func::convert_const_compared_to_int_field
convert_const_to_int
There is the following code snippet in the function convert_const_to_int()
at the line item_cmpfunc.cc:448
bool save_field_value= (field_item->const_item() ||
!(field->table->status & STATUS_NO_RECORD));
Since field->table->status has bits STATUS_NO_RECORD set the variable
save_field_value is false and therefore neither the method
Field_longlong::val_int() nor the method Field_longlong::store is called
on the Field instance that has the numeric value -1.
That is the reason why first execution of the Prepared Statement for the query
'SELECT * FROM v1 WHERE field1 <=> NULL'
is successful.
On second running of the statement 'EXECUTE stmt' a new temporary tables
is also created by running the calls trace #1 but the trace #2 is not executed
by the reason that data member SELECT_LEX::first_cond_optimization has been set
to false on first execution of the prepared statemet (in the method
JOIN::optimize_inner()). As a consequence, the data member TABLE::status for
a temporary table just created doesn't have the flags STATUS_NO_RECORD set and
therefore on re-execution of the prepared statement the methods
Field_longlong::val_int() and Field_longlong::store() are called for the field
having the value -1 and the DBUG_ASSERT(!result) is fired.
To fix the issue the data member TABLE::status has to be assigned the value
STATUS_NO_RECORD in every place where the macros empty_record() is called
to emptify a record for just instantiated TABLE object created on behalf
the new temporary table.
Followup to fix for MDEV-25858: When test_if_skip_sort_order() decides
to use an index to satisfy ORDER BY ... LIMIT clause, it should
disable "Range Checked for Each Record" optimization.
Do this in all cases.
This bug was introduced by commit be00e279c6
The commit was applied for the task MDEV-6480 that allowed to remove top
level disjuncts from WHERE conditions if the range optimizer evaluated them
as always equal to FALSE/NULL.
If such disjuncts are removed the WHERE condition may become an AND formula
and if this formula contains multiple equalities the field JOIN::item_equal
must be updated to refer to these equalities. The above mentioned commit
forgot to do this and it could cause crashes for some queries.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
Do not print illegal table field names for non-top-level SELECT list,
they will not be refered in any case but create problem for parsing
of printed result.
Uninitialized ref_pointer_array[] because setup_fields() got empty
fields list. mysql_multi_update() for some reason does that by
substituting the fields list with empty total_list for the
mysql_select() call (looks like wrong merge since total_list is not
used anywhere else and is always empty). The fix would be to return
back the original fields list. But this fails update_use_source.test
case:
--error ER_BAD_FIELD_ERROR
update v1 set t1c1=2 order by 1;
Actually not failing the above seems to be ok.
The other fix would be to keep resolve_in_select_list false (and that
keeps outer context from being resolved in
Item_ref::fix_fields()). This fix is more consistent with how SELECT
behaves:
--error ER_SUBQUERY_NO_1_ROW
select a from t1 where a= (select 2 from t1 having (a = 3));
So this patch implements this fix.
On deadlock transaction is rolled back (and trx->state is cleared) but
SELECT continued the loop because evaluate_join_record() ignored the
error status returned from lower join evaluation. val_int() does not
return error status so it is checked by thd->is_error().
Test case was created by Thirunarayanan Balathandayuthapani
<thiru@mariadb.com>
instead of original name of the column
When doing refactoring of temporary table field creation a mistake was
done when copying the column name when creating internal temporary tables.
For internal temporary tables we should use the original field name, not
the item name (= alias).
MDEV-16026: Forbid global system_versioning_asof in non-default time zone
* store `system_versioning_asof` in unix time;
* both session and global vars are processed in session timezone;
* setting `default` does not copy global variable anymore. Instead, it sets
system_time to SYSTEM_TIME_UNSPECIFIED, which means that no 'AS OF' time
is applied and `now()` can be assumed
As a regression, we cannot assign values below 1970 (UTC) anymore
MDEV-16481: set global system_versioning_asof=sf() crashes in specific case
* sys_vars.h: add `MYSQL_TIME` field to `set_var::save_result`
* sys_vars.ic: get rid of calling `var->value->get_date()` from
`Sys_var_vers_asof::update()`
* versioning.sysvars: add test; remove double warning
refactor Sys_var_vers_asof
* inherit from sys_var rather than Sys_var_enum
* remove junk "DEFAULT" keyword. There is DEFAULT in SQL grammar for it.
* make all conversions in check() to avoid possible errors
* avoid double var->value evaluation, which could
consequence in undefined behavior
Analysis: When we have INSERT/REPLACE returning with qualified asterisk in the
RETURNING clause, '*' is not resolved properly because of wrong context.
context->table_list is NULL or has incorrect table because context->table_list
has tables from the FROM clause. For INSERT/REPLACE...SELECT...RETURNING,
context->table_list has table we are inserting from. While in other
INSERT/REPLACE syntax, context->table_list is NULL because there is no FROM
clause.
Fix: If filling fields instead of '*' for qualified asterisk in RETURNING,
use first_name_resolution_table for correct resolution of item.
The bug is caused by the following reasons:
* spider_group_by_handler::init_scan() generates a query for a data node.
* The function adds DISTINCT if and only if
spider_group_by_handler::query::distinct is TRUE.
* spider_group_by_handler::query::distinct is set to the value of
JOIN::select_distinct in JOIN::make_aggr_tables_info().
* In the test case, DISTINCT is not added because JOIN::select_distinct
is FALSE at the call of JOIN::make_aggr_tables_info().
Why JOIN::select_distinct is set to FALSE? That is because the function
JOIN::optimize_stage2() convert DISTINCT into GROUP BY and then optimizes
away GROUP BY.
SQL processor failed to catch references to unknown columns and other
errors of the phase of semantic analysis in the specification of a
hanging recursive CTE. This happened because the function
With_clause::prepare_unreferenced_elements() failed to detect a CTE as
a hanging CTE if the CTE was recursive.
Fixing this problem in the code of the mentioned function opened another
problem: EXPLAIN started including the lines for the specifications of
hanging recursive CTEs in its output. This problem also was fixed in this
patch.
Approved by Dmitry Shulga <dmitry.shulga@mariadb.com>
If test_if_skip_sort_order() decides to use an index to produce required
ordering, it should disable "Range Checked for each record" optimization.
This is because Range-Checked-for-each-record may decide to use an index
(or an index_merge) which will not produce the required ordering.
Reformulate mark_columns_used_by_index* function family in a more laconic
way:
mark_columns_used_by_index -> mark_index_columns
mark_columns_used_by_index_for_read_no_reset -> mark_index_columns_for_read
mark_columns_used_by_index_no_reset -> mark_index_columns_no_reset
static mark_index_columns -> do_mark_index_columns
Port the following patch from MySQL:
commit 1b2e8ea269c80cb93cc79d8be934c40b1c58e947
Author: Kailasnath Nagarkar <kailasnath.nagarkar@oracle.com>
Date: Fri Nov 30 16:43:13 2018 +0530
Bug #20939184: INNODB: UNLOCK ROW COULD NOT FIND A 2 MODE
LOCK ON THE RECORD
Issue:
------
Consdier tables t1 and t2 such that t1 has multiple rows
and join condition for t1 left join t2 results in only
single row from t2.
In this case, access to table t2 is const since there
is a single row that qualifies the join condition.
However, while executing the query, attempt is made to
unlock t2's row multiple times.
The current algorithm to fetch rows approximates to:
1) Retrieve the row for t1.
2) Retrieve the row for t2.
3) Apply the join conditions.
a) If condition evaluates to true:
Project the row to the result.
b) If condition evaluates to false:
i) If t2's qep_tab->not_null_complement is true,
unlock t2's row.
ii) Null-complement the row by calling
"evaluate_null_complemented_join_record()". In
this function qep_tab->not_null_complement is
set to false.
The t2's only one row, that qualifies join condition,
is unlocked in Step i) when t1's row is evaluated to
false.
When t1's next row is also evaluated to false, another
attempt is made to unlock t2's already unlocked row.
This results in following error being logged in error.log:
"[ERROR] InnoDB: Unlock row could not find a 3 mode lock on
the record. Current statement:
select * from t1 left join t2 ......"
Solution:
---------
When a table's access method is "const", set record unlock
method for this table to do no operation.
