MDEV-28621: group by optimization incorrectly removing subquery where subject buried in a function
Workaround patch: Do not remove GROUP BY clause when it has
subquer(ies) in it.
remove_redundant_subquery_clauses() removes redundant GROUP BY clause
from queries in form:
expr IN (SELECT no_aggregates GROUP BY ...)
expr {CMP} {ALL|ANY|SOME} (SELECT no_aggregates GROUP BY ...)
This hits problems when the GROUP BY clause itself has subquer(y/ies).
This patch is just a workaround: it disables removal of GROUP BY clause
if the clause has one or more subqueries in it.
Tests:
- subselect_elimination.test has all known crashing cases.
- subselect4.result, insert_select.result are updated.
Note that in some cases results of SELECT are changed too (not just
EXPLAINs). These are caused by non-deterministic SQL: when running a
query like:
x > ANY( SELECT col1 FROM t1 GROUP BY constant_expression)
without removing the GROUP BY, the executor is free to pick the value
of t1.col1 from any row in the GROUP BY group (denote it $COL1_VAL).
Then, it computes x > ANY(SELECT $COL1_VAL).
When running the same query and removing the GROUP BY:
MDEV-34055 Assertion '...' failure or corruption errors upon REPAIR on Aria tables
The problem was two fold:
- REPAIR TABLE t1 USE_FRM did not work for transactional
Aria tables (Table was thought to be repaired, which it was not) which
caused issues in later usage of the table.
- When swapping tmp_data file to data file, sort_info files where not
updated. This caused problems if there was several unique keys and
there was a duplicate for the second key.
4bc1860...
by
Galina Shalygina <email address hidden>
MDEV-23878 Wrong result with semi-join and splittable derived table
Due to this bug a wrong result might be expected from queries with
an IN subquery predicate in the WHERE clause and a derived table in the
FROM clause to which split optimization could be applied.
The function JOIN::fix_all_splittings_in_plan() used the value of the
bitmap JOIN::sjm_lookup_tables() such as it had been left after the
search for the best plan for the select containing the splittable
derived table. That value could not be guaranteed to be correct. So the
recalculation of this bitmap is needed to exclude the plans with key
accesses from SJM lookup tables.
