with joins, SQ, ORDER BY, semijoin=on
A bug in get_sort_by_table() could mislead the function
setup_semijoin_dups_elimination(). As a result the optimizer
could produce invalid execution plans for queries with ORDER BY
and subquery predicates that could be converted to semi-joins.
The fix for bug mdev-5104 did not take into account that
for any call of setup_order the size of ref_array must
be big enough. This patch fixes this problem.
The crash was caused by this problem:
get_best_group_min_max() tries to construct query plans for keys that
are not processed by the range optimizer. This wasn't a problem as long
as SEL_TREE::keys was an array of MAX_KEY elements.
However, now it is a Mem_root_array and only has elements for the used
keys, and get_best_group_min_max attempts to address beyond the end of
the array.
The obvious way to fix the crash was to port (and improve) a part of
96fcfcbd7b5120e8f64fd45985001eca8d36fbfb from mysql-5.7. This makes
get_best_group_min_max not to consider indexes that Mem_root_arrays
have no element for.
After that, I got non-sensical query plans (see MDEV-10325 for details).
Fixed that by making get_best_group_min_max to check if the index is in
table->keys_in_use_for_group_by bitmap.
Post-fix #2:
- Update test results
- Make the optimization conditional under @@optimizer_switch flag.
- The optimization is now disabled by default, so .result files
are changed back to be what they were before the MDEV-8989 patch.
Variant #4 of the fix.
Make ORDER BY optimization functions take into account multiple
equalities. This is done in several places:
- remove_const() checks whether we can sort the first table in the
join, or we need to put rows into temp.table and then sort.
- test_if_order_by_key() checks whether there are indexes that
can be used to produce the required ordering
- make_unireg_sortorder() constructs sort criteria for filesort.
In original code, sometimes one got an automatic DEFAULT value in some cases, in other cases not.
For example:
create table t1 (a int primary key) - No default
create table t2 (a int, primary key(a)) - DEFAULT 0
create table t1 SELECT .... - Default for all fields, even if they where defined as NOT NULL
ALTER TABLE ... MODIFY could sometimes add an unexpected DEFAULT value.
The patch is quite big because we had some many test cases that used
CREATE ... SELECT or CREATE ... (...PRIMARY KEY(xxx)) which doesn't have an automatic DEFAULT anymore.
Other things:
- Removed warnings from InnoDB when waiting from semaphore (got this when testing things with --big)
The problem was caused by the following scenario:
- range optimizer picks an index IDX1 which doesn't match the ORDER BY ...
LIMIT clause.
- test_if_skip_sort_order() decides to switch to index IDX2 which matches
the ORDER BY ... LIMIT.
- it runs SQL_SELECT::test_quick_select() for the second time to produce
an quick select for IDX2.
- However, test_quick_select() would figure that full index scan on IDX1
is still cheaper (its calculations ignore the LIMIT n).
Fixed this by
- passing force_quick_range=true to test_quick_select()
- in test_quick_select, don't consider full index scans if the mentioned
parameter is true.
Numerous changes in .result files are caused by test_quick_select() being
run after "early/late NULLs filtering" feature has injected NOT NULL
condition.
- When a JOIN has both "optimization tabs" (JOIN_TABs used to
read the base tables and do the join operation) and also
has "execution tabs" (a JOIN_TAB that is to produce result set
that is sent to the client), do not forget to call JOIN_TAB::cleanup()
for the execution JOIN_TAB.
This only happend when using an ORDER BY on a primary key part, where all other key parts where constant.
Remove of duplicated expressions in ORDER BY (as the old code did this in some strange cases)
mysql-test/r/group_by.result:
Fixed results to take into account that duplicate order by parts are now deleted
mysql-test/r/group_by_innodb.result:
Ensure extended keys are on
mysql-test/r/innodb_ext_key.result:
More tests
mysql-test/r/order_by.result:
More tests
mysql-test/t/group_by.test:
Fixed results to take into account that duplicate order by parts are now deleted
mysql-test/t/group_by_innodb.test:
Ensure extended keys are on
mysql-test/t/innodb_ext_key.test:
More tests
mysql-test/t/order_by.test:
More tests
sql/sql_select.cc:
Fixed bug where we looked at extended key parts when we shouldn't
Remove of duplicated expressions in ORDER BY
sql/table.cc:
Indentation fixes
Backport the fix olav.sandstaa@sun.com-20101102184747-qfuntqwj021imy9r:
"Fix for Bug#52660 Perf. regr. using ICP for MyISAM on range queries on an index containing TEXT"
(together with further fixes in that code) into MyISAM and Aria.
The bug could caused a crash when the server executed a query with
ORDER by and sort_buffer_size was set to a small enough number.
It happened because the small sort buffer did not allow to allocate
all merge buffers in it.
Made sure that the allocated sort buffer would be big enough
to contain all possible merge buffers.
sql/sql_insert.cc:
CREATE ... IF NOT EXISTS may do nothing, but
it is still not a failure. don't forget to my_ok it.
******
CREATE ... IF NOT EXISTS may do nothing, but
it is still not a failure. don't forget to my_ok it.
sql/sql_table.cc:
small cleanup
******
small cleanup
of the 5.3 code line after a merge with 5.2 on 2010-10-28
in order not to allow the cost to access a joined table to be equal
to 0 ever.
Expanded data sets for many test cases to get the same execution plans
as before.
We must allocate a larger ref_pointer_array. We failed to account for extra
items allocated here:
#0 find_order_in_list
uint el= all_fields.elements;
all_fields.push_front(order_item); /* Add new field to field list. */
ref_pointer_array[el]= order_item;
order->item= ref_pointer_array + el;
#1 setup_order
#2 setup_without_group
#3 JOIN::prepare
mysql-test/r/order_by.result:
New test case.
mysql-test/r/union.result:
New test case.
mysql-test/t/order_by.test:
New test case.
mysql-test/t/union.test:
New test case.
sql/sql_lex.cc:
find_order_in_list() may need some extra space, so multiply og_num by two.
sql/sql_union.cc:
For UNION, the 'n_sum_items' are accumulated in the "global_parameters" select_lex.
This number must be propagated to setup_ref_array()
When preparing a 'fake_select_lex' we need to use global_parameters->order_list
rather than fake_select_lex->order_list (see comments inside st_select_lex_unit::cleanup)
- Set the default
- Adjust the testcases so that 'new' tests are run with optimizations turned on.
- Pull out relevant tests from "irrelevant" tests and run them with optimizations on.
- Run range.test and innodb.test with both mrr=on and mrr=off
Resolved all conflicts, bad merges and fixed a few minor bugs in the code.
Commented out the queries from multi_update, view, subselect_sj, func_str,
derived_view, view_grant that failed either with crashes in ps-protocol or
with wrong results.
The failures are clear indications of some bugs in the code and these bugs
are to be fixed.
- "Using MRR" is no longer shown with range access.
- Instead, both range and BKA accesses will show one of the following:
= "Rowid-ordered scan"
= "Key-ordered scan"
= "Key-ordered Rowid-ordered scan"
depending on whether DS-MRR implementation will do scan keys in order, rowids in order,
or both.
- The patch also introduces a way for other storage engines/MRR implementations to
pass information to EXPLAIN output about the properties of employed MRR scans.
