This bug prevented building conditions that could be pushed into a derived
table if the derived table was used in a query of a stored procedure and
the conditions contained local variables of the procedure. This could lead
to a slow execution of the procedure.
Also in some cases the bug prevented building conditions that could be
pushed from the HAVING condition into the WHERE condition of a query if
the conditions to be built used local variables of a stored procedure.
To failure to build such pushable conditions was due to lack of a proper
implementation of the virtual method to copy items for the objects of the
class Item_splocal.
Approved by Igor Babaev <igor@mariadb.com>
who had to change the original fix that just added the regular copying of
the nodes of the Item_splocal class to take into account the wrappers
do_get_copy() and do_build_clone() introduced after the fix had been
prepared. He also changed the test case to demonstrate that the fix
was really needed for pushdown from HAVING into WHERE.
MDEV-28127 did is_equal() which compared vcol expressions
literally. But another table vcol expression is not equal because of
different table name.
We implement another comparison method is_identical() which respects
different table name in vcol comparison. If any field item points to
table_A and compared field item points to table_B, such items are
treated as equal in (table_A, table_B) comparison. This is done by
cloning table_B expression and renaming any table_B entries to table_A
in it.
MDEV-32329 (patch) pushdown from having into where: Server crashes at sub_select
When generating an Item_equal with a Item_ref that refers to a field
outside of a subselect, remove_item_direct_ref() causes the dependency
(depended_from) on the outer select to be lost, which causes trouble
for code downstream that can no longer determine the scope of the Item.
Not calling remove_item_direct_ref() retains the Item's dependency.
Test cases from MDEV-32395 and MDEV-32329 are included.
Some fixes from other developers:
Monty:
- Fixed wrong code in Item_equal::create_pushable_equalities()
that could cause wrong item to be used if there was no matching items.
Daniel Black:
- Added test cases from MDEV-32329
Igor Babaev:
- Provided fix for removing call to remove_item_direct_ref() in
eliminate_item_equal()
MDEV-32395: update_depend_map_for_order: SEGV at /mariadb-11.3.0/sql/sql_select.cc:16583
Include test cases from MDEV-32329.
When binding to NULL, DEFAULT or IGNORE from an Item value, Item_param did not
change m_type_handler, so its value remained from the previous bind.
Thid led to DBUG_ASSERTs in Item_param::get_date() and
Timestamp_or_zero_datetime_native_null.
Fix:
Set Item_param::m_type_handler to &type_handler_null when
binding from an Item returning NULL.
This patch also fixes MDEV-35427.
Two problem solved:
1) Item_default_value makes a shallow copy so the copy
should not delete field belong to the Item
2) Item_default_value should not inherit
derived_field_transformer_for_having and
derived_field_transformer_for_where (in this variant
pushing DEFAULT(f) is prohibited (return NULL) but
if return "this" it will be allowed (should go with
a lot of tests))
Search conditions were evaluated using val_int(), which was wrong.
Fixing the code to use val_bool() instead.
Details:
- Adding a new item_base_t::IS_COND flag which marks Items used
as <search condition> in WHERE, HAVING, JOIN ON, CASE WHEN clauses.
The flag is at the parse time.
These expressions must be evaluated using val_bool() rather than val_int().
Note, the optimizer creates more Items which are used as search conditions.
Most of these items are not marked with IS_COND yet. This is OK for now,
but eventually these Items can also be fixed to have the flag.
- Adding a method Item::is_cond() which tests if the Item has the IS_COND flag.
- Implementing Item_cache_bool. It evaluates the cached expression using
val_bool() rather than val_int().
Overriding Type_handler_bool::Item_get_cache() to create Item_cache_bool.
- Implementing Item::save_bool_in_field(). It uses val_bool() rather than
val_int() to evaluate the expression.
- Implementing Type_handler_bool::Item_save_in_field()
using Item::save_bool_in_field().
- Fixing all Item_bool_func descendants to implement a virtual val_bool()
rather than a virtual val_int().
- To find places where val_int() should be fixed to val_bool(), a few
DBUG_ASSERT(!is_cond()) where added into val_int() implementations
of selected (most frequent) classes:
Item_field
Item_str_func
Item_datefunc
Item_timefunc
Item_datetimefunc
Item_cache_bool
Item_bool_func
Item_func_hybrid_field_type
Item_basic_constant descendants
- Fixing all places where DBUG_ASSERT() happened during an "mtr" run
to use val_bool() instead of val_int().
A mixture of a multi-byte *TEXT column and a short binary column
produced a too large column.
For example, COALESCE(tinytext_utf8mb4, short_varbinary)
produced a BLOB column instead of an expected TINYBLOB.
- Adding a virtual method Type_all_attributes::character_octet_length(),
returning max_length by default.
- Overriding Item_field::character_octet_length() to extract
the octet length from the underlying Field.
- Overriding Item_ref::character_octet_length() to extract
the octet length from the references Item (e.g. as VIEW fields).
- Fixing Type_numeric_attributes::find_max_octet_length() to
take the octet length using the new method character_octet_length()
instead of accessing max_length directly.
New runtime type diagnostic (MDEV-34490) has detected that classes
Item_func_eq, Item_default_value and Item_date_literal_for_invalid_dates
incorrectly return an instance of its ancestor classes when being cloned.
This commit fixes that.
Additionally, it fixes a bug at Item_func_case_simple::do_build_clone()
which led to an endless loop of cloning functions calls.
Reviewer: Oleksandr Byelkin <sanja@mariadb.com>
New runtime diagnostic introduced with MDEV-34490 has detected
that `Item_int_with_ref` incorrectly returns an instance of its ancestor
class `Item_int`. This commit fixes that.
In addition, this commit reverts a part of the diagnostic related
to `clone_item()` checks. As it turned out, `clone_item()` is not required
to return an object of the same class as the cloned one. For example,
look at `Item_param::clone_item()`: it can return objects of `Item_null`,
`Item_int`, `Item_string`, etc, depending on the object state.
So the runtime type diagnostic is not applicable to `clone_item()` and
is disabled with this commit.
As the similar diagnostic failures are expected to appear again
in the future, this commit introduces a new test file in the main suite:
item_types.test, and new test cases may be added to this file
Reviewer: Oleksandr Byelkin <sanja@mariadb.com>
The `Item` class methods `get_copy()`, `build_clone()`, and `clone_item()`
face an issue where they may be defined in a descendant class
(e.g., `Item_func`) but not in a further descendant (e.g., `Item_func_child`).
This can lead to scenarios where `build_clone()`, when operating on an
instance of `Item_func_child` with a pointer to the base class (`Item`),
returns an instance of `Item_func` instead of `Item_func_child`.
Since this limitation cannot be resolved at compile time, this commit
introduces runtime type checks for the copy/clone operations.
A debug assertion will now trigger in case of a type mismatch.
`get_copy()`, `build_clone()`, and `clone_item()` are no more virtual,
but virtual `do_get_copy()`, `do_build_clone()`, and `do_clone_item()`
are added to the protected section of the class `Item`.
Additionally, const qualifiers have been added to certain methods
to enhance code reliability.
Reviewer: Oleksandr Byelkin <sanja@mariadb.com>
from HAVING
The bug is caused by refixing of the constant subquery in pushdown from
HAVING into WHERE optimization.
Similarly to MDEV-29363 in the problematic query two references of the
constant subquery are used. After the pushdown one of the references of the
subquery is pushed into WHERE-clause and the second one remains as the part
of the HAVING-clause.
Before the represented fix, the constant subquery reference that was going to
be pushed into WHERE was cleaned up and fixed. That caused the changes of
the subquery itself and, therefore, changes for the second reference that
remained in HAVING. These changes caused a crash.
To fix this problem all constant objects that are going to be pushed into
WHERE should be marked with an IMMUTABLE_FL flag. Objects marked with this
flag are not cleaned up or fixed in the pushdown optimization.
Approved by Igor Babaev <igor@mariadb.com>
The crash is caused by the attempt to refix the constant subquery during
pushdown from HAVING into WHERE optimization.
Every condition that is going to be pushed into WHERE clause is first
cleaned up, then refixed. Constant subqueries are not cleaned or refixed
because they will remain the same after refixing, so this complicated
procedure can be omitted for them (introduced in MDEV-21184).
Constant subqueries are marked with flag IMMUTABLE_FL, that helps to miss
the cleanup stage for them. Also they are marked as fixed, so refixing is
also not done for them.
Because of the multiple equality propagation several references to the same
constant subquery can exist in the condition that is going to be pushed
into WHERE. Before this patch, the problem appeared in the following way.
After the first reference to the constant subquery is processed, the flag
IMMUTABLE_FL for the constant subquery is disabled.
So, when the second reference to this constant subquery is processed, the
flag is already disabled and the subquery goes through the procedure of
cleaning and refixing. That causes a crash.
To solve this problem, IMMUTABLE_FL should be disabled only after all
references to the constant subquery are processed, so after the whole
condition that is going to be pushed is cleaned up and refixed.
Approved by Igor Babaev <igor@maridb.com>
Fixing applying the COLLATE clause to a parameter caused an error error:
COLLATION '...' is not valid for CHARACTER SET 'binary'
Fix:
- Changing the collation derivation for a non-prepared Item_param
to DERIVATION_IGNORABLE.
- Allowing to apply any COLLATE clause to expressions with DERIVATION_IGNORABLE.
This includes:
1. A non-prepared Item_param
2. An explicit NULL
3. Expressions derived from #1 and #2
For example:
SELECT ? COLLATE utf8mb_unicode_ci;
SELECT NULL COLLATE utf8mb_unicode_ci;
SELECT CONCAT(?) COLLATE utf8mb_unicode_ci;
SELECT CONCAT(NULL) COLLATE utf8mb_unicode_ci
- Additional change: preserving the collation of an expression when
the expression gets assigned to a PS parameter and evaluates to SQL NULL.
Before this change, the collation of the parameter was erroneously set
to &my_charset_binary.
- Additional change: removing the multiplication to mbmaxlen from the
fix_char_length_ulonglong() argument, because the multiplication already
happens inside fix_char_length_ulonglong().
This fixes a too large column size created for a COLLATE clause.
Some fixes related to commit f838b2d799 and
Rows_log_event::do_apply_event() and Update_rows_log_event::do_exec_row()
for system-versioned tables were provided by Nikita Malyavin.
This was required by test versioning.rpl,trx_id,row.
UPDATE statement that is run in PS mode and uses positional parameter
handles columns declared with the clause DEFAULT NULL incorrectly in
case the clause DEFAULT is passed as actual value for the positional
parameter of the prepared statement. Similar issue happens in case
an expression specified in the DEFAULT clause of table's column definition.
The reason for incorrect processing of columns declared as DEFAULT NULL
is that setting of null flag for a field being updated was missed
in implementation of the method Item_param::assign_default().
The reason for incorrect handling of an expression in DEFAULT clause is
also missed saving of a field inside implementation of the method
Item_param::assign_default().
As a result of this bug the second execution of the prepared statement
created for select from materialized view could return a wrong result set if
- the specification of the view used a left join
- an inner table the left join was a mergeable derived table
- the derived table contained a constant column.
The problem appeared because the flag 'maybe-null' of the wrapper
Item_direct_view_ref constructed for the constant field of the mergeable
derived table was not set to 'true' on the second execution of the
prepared statement.
The patch always sets this flag properly when calling the function
Item_direct_view_ref::set_null_ref-table(). The latter is invoked in
Item_direct_view_ref constructor if it is created for some reference of
a constant column belonging to a mergeable derived table.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
