When JOIN::destroy() is called for a JOIN object that has
- join->tmp_join != NULL
- also has join->table[0]->sort
then the latter was not cleaned up.
This could cause a memory leak and/or asserts in the subsequent queries.
Fixed by adding a cleanup call.
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.
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
Analysis:
The crash is a result of incorrect analysis of whether a secondary key
can be extended with a primary in order to compute ORDER BY. The analysis
is done in test_if_order_by_key(). This function doesn't take into account
that the primary key may in fact index the same columns as the secondary
key. For the test query test_if_order_by_key says that there is an extended
key with total 2 keyparts.
At the same time, the condition
if (pkinfo->key_part[i].field->key_start.is_set(nr))
in test_if_cheaper_oredring() becomes true for (i == 0), which results in
an invalid access to rec_per_key[-1].
Solution:
The best solution would be to reuse KEY::ext_key_parts that is already computed
by open_binary_frm(), however after detailed analysis the conclusion is that
the change would be too intrusive for a GA release.
The solution for 5.5 is to add a guard for the case when the 0-th key part is
considered, and to assume that all keys will be scanned in this case.
