Search conditions were evaluated using val_int(), which was wrong.
Fixing the code to use val_bool() instead.
Details:
- Adding a new item_base_t::IS_COND flag which marks Items used
as <search condition> in WHERE, HAVING, JOIN ON, CASE WHEN clauses.
The flag is at the parse time.
These expressions must be evaluated using val_bool() rather than val_int().
Note, the optimizer creates more Items which are used as search conditions.
Most of these items are not marked with IS_COND yet. This is OK for now,
but eventually these Items can also be fixed to have the flag.
- Adding a method Item::is_cond() which tests if the Item has the IS_COND flag.
- Implementing Item_cache_bool. It evaluates the cached expression using
val_bool() rather than val_int().
Overriding Type_handler_bool::Item_get_cache() to create Item_cache_bool.
- Implementing Item::save_bool_in_field(). It uses val_bool() rather than
val_int() to evaluate the expression.
- Implementing Type_handler_bool::Item_save_in_field()
using Item::save_bool_in_field().
- Fixing all Item_bool_func descendants to implement a virtual val_bool()
rather than a virtual val_int().
- To find places where val_int() should be fixed to val_bool(), a few
DBUG_ASSERT(!is_cond()) where added into val_int() implementations
of selected (most frequent) classes:
Item_field
Item_str_func
Item_datefunc
Item_timefunc
Item_datetimefunc
Item_cache_bool
Item_bool_func
Item_func_hybrid_field_type
Item_basic_constant descendants
- Fixing all places where DBUG_ASSERT() happened during an "mtr" run
to use val_bool() instead of val_int().
JOIN_CACHE has a light-weight initialization mode that's targeted at
EXPLAINs. In that mode, JOIN_CACHE objects are not able to execute.
Light-weight mode was used whenever the statement was an EXPLAIN. However
the EXPLAIN can execute subqueries, provided they enumerate less than
@@expensive_subquery_limit rows.
Make sure we use light-weight initialization mode only when the select is
more expensive @@expensive_subquery_limit.
Also add an assert into JOIN_CACHE::put_record() which prevents its use
if it was initialized for EXPLAIN only.
This patch fixes a performance regression introduced in the patch for the
bug MDEV-21104. The performance regression could affect queries for which
join buffer was used for an outer join such that its on expression from
which a conjunctive condition depended only on outer tables can be
extracted. If the number of records in the join buffer for which this
condition was false greatly exceeded the number of other records the
slowdown could be significant.
If there is a conjunctive condition extracted from the ON expression
depending only on outer tables this condition is evaluated when interesting
fields of each survived record of outer tables are put into the join buffer.
Each such set of fields for any join operation is supplied with a match
flag field used to generate null complemented rows. If the result of the
evaluation of the condition is false the flag is set to MATCH_IMPOSSIBLE.
When looking in the join buffer for records matching a record of the
right operand of the outer join operation the records with such flags
are not needed to be unpacked into record buffers for evaluation of on
expressions.
The patch for MDEV-21104 fixing some problem of wrong results when
'not exists' optimization by mistake broke the code that allowed to
ignore records with the match flag set to MATCH_IMPOSSIBLE when looking
for matching records. As a result such records were unpacked for each
record of the right operand of the outer join operation. This caused
significant execution penalty in some cases.
One of the test cases added in the patch can be used only for demonstration
of the restored performance for the reported query. The second test case is
needed to demonstrate the validity of the fix.
The fix is to return 3-state value from Range_rowid_filter::build()
call:
1. The filter was built successfully;
2. The filter was not built, but the error was not fatal, i.e. there is
no need to rollback transaction. For example, if the size of container to
storevrow ids is not enough;
3. The filter was not built because of fatal error, for example,
deadlock or lock wait timeout from storage engine. In this case we
should stop query plan execution and roll back transaction.
Reviewed by: Sergey Petrunya
This is also related to
MDEV-31348 Assertion `last_key_entry >= end_pos' failed in virtual bool
JOIN_CACHE_HASHED::put_record()
Valgrind exposed a problem with the join_cache for hash joins:
=25636== Conditional jump or move depends on uninitialised value(s)
==25636== at 0xA8FF4E: JOIN_CACHE_HASHED::init_hash_table()
(sql_join_cache.cc:2901)
The reason for this was that avg_record_length contained a random value
if one had used SET optimizer_switch='optimize_join_buffer_size=off'.
This causes either 'random size' memory to be allocated (up to
join_buffer_size) which can increase memory usage or, if avg_record_length
is less than the row size, memory overwrites in thd->mem_root, which is
bad.
Fixed by setting avg_record_length in JOIN_CACHE_HASHED::init()
before it's used.
There is no test case for MDEV-31893 as valgrind of join_cache_notasan
checks that.
I added a test case for MDEV-31348.
This is also related to
MDEV-31348 Assertion `last_key_entry >= end_pos' failed in virtual bool
JOIN_CACHE_HASHED::put_record()
Valgrind exposed a problem with the join_cache for hash joins:
=25636== Conditional jump or move depends on uninitialised value(s)
==25636== at 0xA8FF4E: JOIN_CACHE_HASHED::init_hash_table()
(sql_join_cache.cc:2901)
The reason for this was that avg_record_length contained a random value
if one had used SET optimizer_switch='optimize_join_buffer_size=off'.
This causes either 'random size' memory to be allocated (up to
join_buffer_size) which can increase memory usage or, if avg_record_length
is less than the row size, memory overwrites in thd->mem_root, which is
bad.
Fixed by setting avg_record_length in JOIN_CACHE_HASHED::init()
before it's used.
There is no test case for MDEV-31893 as valgrind of join_cache_notasan
checks that.
I added a test case for MDEV-31348.
The problem was that JOIN_CACHE::alloc_buffer() did not check if the
given join_buffer_value is less than the query require.
Added a check for this and disabled join cache if it cannot be used.
- Remove virtual from get_min_join_buffer_size() and
get_max_join_buffer_size().
- Avoid some calls to get_min_buffer_size()
- Simply cache usage in get_..._join_buffer_size()
- Simplify get_max_join_buffer_size() when using optimize_buff_size
- Reindented some long comments
Reviewer: Sergei Petrunia <sergey@mariadb.com>
The old code did set max_records to either number_of_rows
(partial_join_cardinality) or memory size (join_buffer_space_limit)
which did not make sense.
Fixed by setting max_records to number of rows that fits into
join_buffer_size.
Other things:
- Initialize buffer cache values in JOIN_CACHE constructors (safety)
Reviewer: Sergei Petrunia <sergey@mariadb.com>
The problem was that join_buffer_size conflicted with
join_buffer_space_limit, which caused the query to be run without join
buffer. However this caused wrong results as the optimizer assumed
that hash+join buffer would ensure that the equi-join condition
would be satisfied, and didn't check it itself.
Fixed by not using join_buffer_space_limit when
optimize_join_buffer_size=off. This matches the documentation at
https://mariadb.com/kb/en/block-based-join-algorithms
Other things:
- Removed not used variable JOIN_TAB::join_buffer_size_limit
- Give an error if we cannot allocate a join buffer. This can
only happen if the join_buffer variables are wrongly configured or
we are running out of memory.
In the future, instead of returning an error, we could properly
convert the query plan that uses BNL-H join into one that doesn't
use join buffering:
make sure the equi-join condition is checked where appropriate.
Reviewer: Sergei Petrunia <sergey@mariadb.com>
This bug affected queries with nested left joins having the same last inner
table such that not_exists optimization could be applied to the most inner
outer join when optimizer chose to use join buffers. The bug could lead to
producing wrong a result set.
If the WHERE condition a query contains a conjunctive IS NULL predicate
over a non-nullable column of an inner table of a not nested outer join
then not_exists optimization can be applied to tho the outer join. With
this optimization when looking for matches for a certain record from the
outer table of the join the records of the inner table can be ignored
right after the first match satisfying the ON condition is found.
In the case of nested outer joins having the same last inner table this
optimization still can be applied but only if all ON conditions of the
embedding outer joins are satisfied. Such check was missing in the code
that tried to apply not_exists optimization when join buffers were used
for outer join operations.
This problem has been already fixed in the patch for bug MDEV-7992. Yet
there it was resolved only for the cases when join buffers were not used
for outer joins.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
by compound index
This typo bug may lead to wrong result sets for equi-join queries where
the join operation is supported by a compound index such that the order of
its components differs from the order of the corresponding columns in
the table the index belongs to. The bug manifests itself only when usage
of the BNLH algorithm is forced.
The fix for the bug was provided by Chu Huaxing.
This bug could affect multi-way join queries with embedded outer joins that
contained a conjunctive IS NULL predicate over a non-nullable column from
inner table of an outer join. The predicate could occur in WHERE condition
or in ON condition. Due to this bug a wrong result set could be returned by
the query. The bug manifested itself only when join buffers were employed
for join operations.
The problem appeared because
- a bug in the function JOIN_CACHE::get_match_flag_by_pos that not always
returned proper match flags for embedding outer joins stored together
with table rows put a join buffer.
- bug in the function JOIN_CACHE::join_matching_records that not always
correctly determined that a row from the buffer could be skipped due
to applied 'not_exists' optimization.
Example:
SELECT * FROM t1 LEFT JOIN ((t2 LEFT JOIN t3 ON c = d) JOIN t4) ON b = e
WHERE e IS NULL;
The patch introduces a new function that finds the match flag for a record
from join buffer specifying the buffer where this flag has to be found.
The function is called JOIN_CACHE::get_match_flag_by_pos_from_join_buffer().
Now this function rather than JOIN_CACHE::get_match_flag_by_pos() is used
in JOIN_CACHE::skip_if_matched() to check whether a record from the join
buffer must be ignored when extending the record by null complements.
Also the code of the function JOIN_CACHE::skip_if_not_needed_match() has
been changed. The function checks whether a record from the join buffer
still may produce some useful extensions.
Also some clarifying comments has been added.
Approved by monty@mariadb.com.
This follows up commit
commit 94a520ddbe and
commit 7c5519c12d.
After these changes, the default test suites on a
cmake -DWITH_UBSAN=ON build no longer fail due to passing
null pointers as parameters that are declared to never be null,
but plenty of other runtime errors remain.
This patch fixes the following defects/bugs.
1. If BKA[H] algorithm was used to join a table for which the optimizer
had decided to employ a rowid filter the filter actually was not built.
2. The patch for the bug MDEV-21356 that added the code canceling pushing
rowid filter into an engine for the table joined with employment of
BKA[H] and MRR was not quite correct for Innodb engine because this
cancellation was done after InnoDB code had already bound the the pushed
filter to internal InnoDB structures.
This bug could happen when queries with nested outer joins were
executed employing join buffers. At such an execution if the method
JOIN_CACHE::join_records() is called when a join buffer has become
full no 'first_unmatched' field should be cleaned up in the JOIN_TAB
structure to which the join cache with this buffer is attached.
This commit is based on the work of Michal Schorm, rebased on the
earliest MariaDB version.
Th command line used to generate this diff was:
find ./ -type f \
-exec sed -i -e 's/Foundation, Inc., 59 Temple Place, Suite 330, Boston, /Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, /g' {} \; \
-exec sed -i -e 's/Foundation, Inc. 59 Temple Place.* Suite 330, Boston, /Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, /g' {} \; \
-exec sed -i -e 's/MA.*.....-1307.*USA/MA 02110-1335 USA/g' {} \; \
-exec sed -i -e 's/Foundation, Inc., 59 Temple/Foundation, Inc., 51 Franklin/g' {} \; \
-exec sed -i -e 's/Place, Suite 330, Boston, MA.*02111-1307.*USA/Street, Fifth Floor, Boston, MA 02110-1335 USA/g' {} \; \
-exec sed -i -e 's/MA.*.....-1307/MA 02110-1335/g' {} \;
Fixed by deleting the sequence if we where not able to initialize it
I also noticed that we didn't always set the error message when
check_killed(), which could lead to aborted queries without error
beeing properly set. Fixed by default setting error message if
check_error() noticed that killed had been called.
This allowed me to remove a lot of calls to thd->send_kill_message().
Handle string length as size_t, consistently (almost always:))
Change function prototypes to accept size_t, where in the past
ulong or uint were used. change local/member variables to size_t
when appropriate.
This fix excludes rocksdb, spider,spider, sphinx and connect for now.
