The earlier pushed fix for the bug was incomplete. It did not remove
the main cause of the problem: the function remove_eq_conds()
removed always true multiple equalities from any conjunct, but did not
adjust the list of them stored in Item_cond_and::cond_equal.current_level.
Simplified the test case for the bug and moved it to another test file.
The fix triggered changes in EXPLAIN EXTENDED for some queries.
When setting Item_func_not_all::test_sum_item or Item_func_not_all::test_sub_item,
reset the other one to NULL - they can never be set both. When a PS is reexecuted,
different executions might be optimized differently and a wrong test_su*_item
might stay set from the previous execution.
1. Transformation of row IN subquery made the same as single value.
2. replace_where_subcondition() made working on several layers of OR/AND because it called on expression before fix_fields().
Singular Item_equal support added.
The problem was that during constant table substitution Item_equal become containing only one constant which was not supported internally.
The loop in the binary search in remove_status_vars() was
incorrectly implemented and could continue infinitely in some cases.
Rewrote the binary search code.
There was 2 problems:
1) coping/moving of the same type (usually casting) as sizeof() (solved in different ways depends on the cause);
2) using 'const' in SSL_CTX::getVerifyCallback() which return object (not reference) and so copy of the object will be created and 'const' has no sens.
Analysis:
st_select_lex_unit::prepare() computes can_skip_order_by as TRUE.
As a result join->prepare() gets called with order == NULL, and
doesn't do name resolution for the inner ORDER clause. Due to this
the prepare phase doesn't detect that the query references non-exiting
function and field.
Later join->optimize() calls update_used_tables() for a non-resolved
Item_field, which understandably has no Field object. This call results
in a crash.
Solution:
Resolve unnecessary ORDER BY clauses to detect if they reference non-exising
objects. Then remove such clauses from the JOIN object.
MDEV-5034:Wrong result on LEFT JOIN with a SELECT SQ or a merge view, UNION in IN subquery
Make reset null_row same as it was set in evaluate_null_complemented_join_record().
The problem was that view firlds detect null_row by not-yet-reset table.
Objects of the classes Item_func_isnull and Item_func_isnotnull
must have the flag sargable set to TRUE.
Set the value of the flag sargable only in constructors of the
classes inherited from Item_int_func.
The bug caused a memory overwrite in the function update_ref_and_keys()
It happened due to a wrong value of SELECT_LEX::cond_count. This value
historically was calculated by the fix_fields method. Now the logic of
calling this method became too complicated and, as a result, this value
is calculated not always correctly.
The patch changes the way how and when the values of SELECT_LEX::cond_count
and of SELECT_LEX::between_count are calculated. The new code does it just at
the beginning of update_ref_and_keys().
For aggregated fields from views/derived tables the possible adjustment
of thd->lex->in_sum_func->max_arg_level in the function Item_field::fix_fields
must be done before we leave the function.
Apparently in a general case a short-cut for the distinct optimization
is invalid if join buffers are used to join tables after the tables whose
values are to selected.
Other fix of maybe_null problem and revert of revno: 3608 "MDEV-3873 & MDEV-3876 & MDEV-3912 : Wrong result (extra rows) with ALL subquery from a MERGE view."
When a non-nullable datetime field is used under an IS NULL predicate
of the WHERE condition in a query with outer joins the remove_eq_conds
function should check whether this field belongs to an inner table
of any outer join that can be, in a general case, a nested outer join.
When in function remove_eq_conds() a sub-formula of the processed condition
is replaced for another formula we should ensure that in the resulting
formula AND/OR levels must alternate.
The patch to fix mdev-4418 turned out to be incorrect.
At the substitution of single row tables in make_join_statistics()
the used multiple equalities may change and references to the new multiple
equalities must be updated. The function remove_eq_conds() takes care of it and
it should be called right after the substitution of single row tables.
Calling it after the call of make_join_statistics was a mistake.
