filesort and init_read_record() for the same table.
This will simplify code for WINDOW FUNCTIONS (MDEV-6115)
- Filesort_info renamed to SORT_INFO and moved to filesort.h
- filesort now returns SORT_INFO
- init_read_record() now takes a SORT_INFO parameter.
- unique declaration is moved to uniques.h
- subselect caching of buffers is now more explicit than before
- filesort_buffer is now reusable even if rec_length has changed.
- filsort_free_buffers() and free_io_cache() calls are removed
- Remove one malloc() when using get_addon_fields()
Other things:
- Added --debug-assert-on-not-freed-memory option to make it easier to
debug some not-freed-memory issues.
"Re-factor the code for post-join operations".
The patch mainly contains the code ported from mysql-5.6 and
created for two essential architectural changes:
1. WL#5558: Resolve ORDER BY execution method at the optimization stage
2. WL#6071: Inline tmp tables into the nested loops algorithm
The first task was implemented for mysql-5.6 by Ole John Aske.
It allows to make all decisions on ORDER BY operation at the optimization
stage.
The second task implemented for mysql-5.6 by Evgeny Potemkin adds JOIN_TAB
nodes for post-join operations that require temporary tables. It allows
to execute these operations within the nested loops algorithm that used to
be used before this task only for join queries. Besides these task moves
all planning on the execution of these operations from the execution phase
to the optimization phase.
Some other re-factoring changes of mysql-5.6 were pulled in, mainly because
it was easier to pull them in than roll them back. In particular all
changes concerning Ref_ptr_array were incorporated.
The port required some changes in the MariaDB code that concerned the
functionality of EXPLAIN and ANALYZE. This was done mainly by Sergey
Petrunia.
create_partition_index_description() had wrong logic to calculate
length of the key value buffer that is used by the range optimizer.
For some reason it used MAX(partitioning_columns_len,
subpartitioning_columns_len) while it should use SUM of these values.
changes in query execution plans.
Fixed by introducing table->rpl_write_set which holds which columns should
be stored in the binary log.
Other things:
- Removed some not needed references to read_set and write_set to make
code really changing read_set and write_set easier to read
(in opt_range.cc)
- Added error handling of failed unpack_current_row()
- Added missing call to mark_columns_needed_for_insert() for DELAYED INSERT
- Removed not used functions in_read_set() and in_write_set()
- In rpl_record.cc, removed not used variable error
The bitmap implementation defines two template Bitmap classes. One
optimized for 64-bit (default) wide bitmaps while the other is used for
all other widths.
In order to optimize the computations, Bitmap<64> class has defined its
own member functions for bitmap operations, the other one, however,
relies on mysys' bitmap implementation (mysys/my_bitmap.c).
Issue 1:
In case of non 64-bit Bitmap class, intersect() wrongly reset the
received bitmap while initialising a new local bitmap structure
(bitmap_init() clears the bitmap buffer) thus, the received bitmap was
getting cleared.
Fixed by initializing the local bitmap structure by using a temporary
buffer and later copying the received bitmap to the initialised bitmap
structure.
Issue 2:
The non 64-bit Bitmap class had the Iterator missing which caused
compilation failure.
Also added a cmake variable to hold the MAX_INDEXES value when supplied
from the command prompt. (eg. cmake .. -DMAX_INDEXES=128U). Checks have
been put in place to trigger build failure if MAX_INDEXES value is
greater than 128.
Test modifications:
* Introduced include/have_max_indexes_[64|128].inc to facilitate
skipping of tests for which the output differs with different
MAX_INDEXES.
* Introduced include/max_indexes.inc which would get modified by cmake
to reflect the MAX_INDEXES value used to build the server. This file
simply sets an mtr variable '$max_indexes' to show the MAX_INDEXES
value, which will then be consumed by the above introduced include file.
* Some tests (portions), dependent on MAX_INDEXES value, have been moved
to separate test files.
When we calculate max_key_len for RANGE_OPT_PARAM::min_key/max_key, take
into account that QUICK_RANGE::QUICK_RANGE for some reason assumes
that there is one more byte there:
max_key((uchar*) sql_memdup(max_key_arg,max_length_arg+1)),
- Turning get_mm_tree_for_const() from a static function into
a protected method in Item.
- Adding a new class Item_bool_func2_with_rev, for the functions and operators
that have a reverse function and can use the range optimizer for
to optimize "value OP field" as "field REV_OP value". Deriving
Item_bool_rowready_func2 and Item_funt_spatial_rel from the new class.
- Removing Item_bool_func2::have_rev_func().
from Item_bool_func::get_mm_leaf() into Field_xxx::can_optimize_range().
This reduces the total amount of virtual calls. Also, it's a prerequisite
change for the pluggable data types.
The crash was caused by range optimizer using RANGE_OPT_PARAM::min_key
(and max_key) to store keys. Buffer size was a good upper bound for
range analysis and partition pruning, but not for EITS selectivity
calculations.
Fixed by making these buffers variable-size. The sizes are calculated
from [pseudo]indexes used for range analysis.
The crash was caused by range optimizer using RANGE_OPT_PARAM::min_key
(and max_key) to store keys. Buffer size was a good upper bound for
range analysis and partition pruning, but not for EITS selectivity
calculations.
Fixed by making these buffers variable-size. The sizes are calculated
from [pseudo]indexes used for range analysis.
- Part 3: Adding mem_root to push_back() and push_front()
Other things:
- Added THD as an argument to some partition functions.
- Added memory overflow checking for XML tag's in read_xml()
Added mandatory thd parameter to Item (and all derivative classes) constructor.
Added thd parameter to all routines that may create items.
Also removed "current_thd" from Item::Item. This reduced number of
pthread_getspecific() calls from 290 to 177 per OLTP RO transaction.
methods in Item_bool_func descendants, which gives some advantages:
- Removing the "bool inv" parameter, as its now available through "this"
for Item_func_between and Item_func_in, and is not needed for the other
Item_func_xxx.
- Removing casts
- Making a step to data types plugings
FIND_USED_PARTITIONS | SQL/OPT_RANGE.CC:3884
Issue:
-----
During partition pruning, first we identify the partition
in which row can reside and then identify the subpartition.
If we find a partition but not the subpartion then we hit
a debug assert. While finding the subpartition we check
the current thread's error status in part_val_int()
function after some operation. In this case the thread's
error status is already set to an error (multiple rows
returned) so the function returns no partition found and
results in incorrect behavior.
SOLUTION:
---------
Currently any error encountered in part_val_int is
considered a "partition not found" type error. Instead of
an assert, a check needs to be done and a valid error
returned.
- Changed ER(ER_...) to ER_THD(thd, ER_...) when thd was known or if there was many calls to current_thd in the same function.
- Changed ER(ER_..) to ER_THD_OR_DEFAULT(current_thd, ER...) in some places where current_thd is not necessary defined.
- Removing calls to current_thd when we have access to thd
Part of this is optimization (not calling current_thd when not needed),
but part is bug fixing for error condition when current_thd is not defined
(For example on startup and end of mysqld)
Notable renames done as otherwise a lot of functions would have to be changed:
- In JOIN structure renamed:
examined_rows -> join_examined_rows
record_count -> join_record_count
- In Field, renamed new_field() to make_new_field()
Other things:
- Added DBUG_ASSERT(thd == tmp_thd) in Item_singlerow_subselect() just to be safe.
- Removed old 'tab' prefix in JOIN_TAB::save_explain_data() and use members directly
- Added 'thd' as argument to a few functions to avoid calling current_thd.
Fixed several optimizer issues relatied to GROUP BY:
a) Refering to a SELECT column in HAVING sometimes calculated it twice, which caused problems with non determinstic functions
b) Removing duplicate fields and constants from GROUP BY was done too late for "using index for group by" optimization to work
c) EXPLAIN SELECT ... GROUP BY did wrongly show 'Using filesort' in some cases involving "Using index for group-by"
a) was fixed by:
- Changed last argument to Item::split_sum_func2() from bool to int to allow more flags
- Added flag argument to Item::split_sum_func() to allow on to specify if the item was in the SELECT part
- Mark all split_sum_func() calls from SELECT with SPLIT_SUM_SELECT
- Changed split_sum_func2() to do nothing if called with an argument that is not a sum function and doesn't include sum functions, if we are not an argument to SELECT.
This ensures that in a case like
select a*sum(b) as f1 from t1 where a=1 group by c having f1 <= 10;
That 'a' in the SELECT part is stored as a reference in the temporary table togeher with sum(b) while the 'a' in having isn't (not needed as 'a' is already a reference to a column in the result)
b) was fixed by:
- Added an extra remove_const() pass for GROUP BY arguments before make_join_statistics() in case of one table SELECT.
This allowes get_best_group_min_max() to optimize things better.
c) was fixed by:
- Added test for group by optimization in JOIN::exec_inner for
select->quick->get_type() == QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX
item.cc:
- Simplifed Item::split_sum_func2()
- Split test to make them faster and easier to read
- Changed last argument to Item::split_sum_func2() from bool to int to allow more flags
- Added flag argument to Item::split_sum_func() to allow on to specify if the item was in the SELECT part
- Changed split_sum_func2() to do nothing if called with an argument that is not a sum function and doesn't include sum functions, if we are not an argument to SELECT.
opt_range.cc:
- Simplified get_best_group_min_max() by calcuating first how many group_by elements.
- Use join->group instead of join->group_list to test if group by, as join->group_list may be NULL if everything was optimized away.
sql_select.cc:
- Added an extra remove_const() pass for GROUP BY arguments before make_join_statistics() in case of one table SELECT.
- Use group instead of group_list to test if group by, as group_list may be NULL if everything was optimized away.
- Moved printing of "Error in remove_const" to remove_const() instead of having it in caller.
- Simplified some if tests by re-ordering code.
- update_depend_map_for_order() and remove_const() fixed to handle the case where make_join_statistics() has not yet been called (join->join_tab is 0 in this case)
Step #8: Adding get_mm_tree() in Item_func, Item_func_between,
Item_func_in, Item_equal. This removes one virtual call item->type()
in queries like:
SELECT * FROM t1 WHERE c BETWEEN const1 AND const2;
SELECT * FROM t1 WHERE c>const;
SELECT * FROM t1 WHERE c IN (const_list);
Step #7 (mostly preparatory for the next step #8):
Splitting the function get_mm_parts() into a virtual method in Item.
This changes a virtual call for item->type() into a virtual call for item->get_mm_tree(),
but also *removes* one virtual call Item_cond::functype(), which used to distinguish
between COND_AND_FUNC vs COND_OR_FUNC.
sql_alloc() has additional costs compared to direct mem_root allocation:
- function call: it is defined in a separate translation unit and can't be
inlined
- it needs to call pthread_getspecific() to get THD::mem_root
It is called dozens of times implicitely at least by:
- List<>::push_back()
- List<>::push_front()
- new (for Sql_alloc derived classes)
- sql_memdup()
Replaced lots of implicit sql_alloc() calls with direct mem_root allocation,
passing through THD pointer whenever it is needed.
Number of sql_alloc() calls reduced 345 -> 41 per OLTP RO transaction.
pthread_getspecific() overhead dropped 0.76 -> 0.59
sql_alloc() overhed dropped 0.25 -> 0.06
mysql-test/r/group_by.result:
Test for MDEV-6855
mysql-test/t/group_by.test:
Test for MDEV-6855
sql/item.h:
Fixed spelling error
sql/opt_range.cc:
Added handling of cond_type == Item::CACHE_ITEM in WHERE clauses for MIN/MAX optimization.
Fixed indentation
