This patch fills a serious flaw in the implementation of common table
expressions. Before this patch an attempt to prepare a statement from
a query with a parameter marker in a CTE that was used more than once
in the query ended up with a bogus error message. Similarly if a statement
in a stored procedure contained a CTE whose specification used a
local variables and this CTE was referred to more than once in the
statement then the server failed to execute the stored procedure returning
a bogus error message on a non-existing field.
The problems appeared due to incorrect handling of parameter markers /
local variables in CTEs that were referred more than once.
This patch fixes the problems by differentiating between the original
occurrences of a parameter marker / local variable used in the
specification of a CTE and the corresponding occurrences used
in copies of this specification. These copies are substituted
instead of non-first references to the CTE.
The idea of the fix and even some code were taken from the MySQL
implementation of the common table expressions.
We do not accept:
1. We did not have this problem (fixed earlier and better)
d982e717ab Bug#27510150: MYSQLDUMP FAILS FOR SPECIFIC --WHERE CLAUSES
2. We do not have such options (an DBUG_ASSERT put just in case)
bbc2e37fe4 Bug#27759871: BACKRONYM ISSUE IS STILL IN MYSQL 5.7
3. Serg fixed it in other way in this release:
e48d775c6f Bug#27980823: HEAP OVERFLOW VULNERABILITIES IN MYSQL CLIENT LIBRARY
materialized derived table/view that uses aliases is done
The problem appears when a column alias inside the materialized derived
table/view t1 definition coincides with the column name used in the
GROUP BY clause of t1. If the condition that can be pushed into t1
uses that ambiguous column name this column is determined as a column that
is used in the GROUP BY clause instead of the alias used in the projection
list of t1. That causes wrong result.
To prevent it resolve_ref_in_select_and_group() was changed.
virtual Item_null_result::get_date() was not overridden.
It used the inherited Item::get_date(), which tests field_type(),
which in case of Item_null_result calls result_field->field_type(),
and result_field is not really always set (e.g. it's not set in the
test case from the bug report).
Overriding Item_null::get_date() like it's done for other val_xxx() methods.
This make the code more symmetric across data types.
In the new reduction, get_date() immediately returns NULL without entering
into any data type specific code.
items in the partitioning function were taking
the table name from the table's field
(in set_field(from_field) in Item_field::fix_fields)
and field's table_name is TABLE::alias.
But alias is changed for every statement, and
can be realloced if next statement uses a longer
alias. But partitioning items are fixed once
and live as long as the TABLE does. So if
an alias is realloced, pointers to the old
alias string will become invalid.
Fix partitioning item table_name to point to
the actual table name instead.
rename to post_fix_fields_part_expr_processor()
because it's only used after fix_fields in
fix_fields_part_func() and can be used for
various post-fix_fields fixups
multiple times with different arguments.
If the ON expression of an outer join is an OR formula with one
of the disjunct being a constant formula then the expression
cannot be null-rejected if the constant formula is true. Otherwise
it can be null-rejected and if so the outer join can be converted
into inner join. This optimization was added in the patch for
mdev-4817. Yet the code had a defect: if the query was used in
a stored procedure with parameters and the constant item contained
some of them then the value of this constant item depended on the
values of the parameters. With some parameters it may be true,
for others not. The validity of conversion to inner join is checked
only once and it happens only for the first call of procedure.
So if the parameters in the first call allowed the conversion it
was done and next calls used the transformed query though there
could be calls whose parameters made the conversion invalid.
Fixed by cheking whether the constant disjunct in the ON expression
originally contained an SP parameter. If so the expression is not
considered as null-rejected. For this check a new item's attribute
was intruduced: Item::with_param. It is calculated for each item
by fix fields() functions.
Also moved the call of optimize_constant_subqueries() in
JOIN::optimize after the call of simplify_joins(). The reason
for this is that after the optimization introduced by the patch
for mdev-4817 simplify_joins() can use the results of execution
of non-expensive constant subqueries and this is not valid.
The implementations of the convert_to_basic_const_item() virtual
function for the Item_cache classes should call cache_value() when
value_cached == NULL.
WRONG VALUES
User variables will have the default session collation
associated with it. And a select which uses it as part of a
union may infer the collation while type merging.
This leads to problems when the result is of DECIMAL type.
Setting the appropriate collation of DECIMAL result type
is missing in 5.7 code base.
Added code to set appropriate collation when the result is
of DECIMAL type during Item_type_holder::join_types().
To disallow equality propagation for DATETIME with non-zero YYYYMMDD part we were setting null_value to true.
This caused issues when we were calculating selectivity for a condition as this returned IMPOSSIBLE WHERE.
The issue is resolved by not setting null_value to true for DATETIME with non-zero YYYYMMDD.
Refactor get_datetime_value() not to create Item_cache_temporal(),
but do it always in ::fix_fields() or ::fix_length_and_dec().
Creating items at the execution time doesn't work very well with
virtual columns and check constraints that are fixed and executed
in different THDs.
Do not assume that it's always item->field_type() - this is not the case
in temporal comparisons (e.g. when comparing DATETIME column with a TIME
literal).
Setting non_null value drops null_value flag.
Part 1 of 3.
Part 2 will be for 10.3 including change of ps.test results.
Part 3 is test for Connector C.
MDEV-14957: JOIN::prepare gets unusable "conds" as argument
Do not touch merged derived (it is irreversible)
Fix first argument of in_optimizer for calls possible before fix_fields()
This reverts commit 7603463a46.
The commit itself is fine, however when disabling volatile, compiler
optimizations mess up our double results due to precision differences.
Revert the patch till a proper solution is found.
