This bug was intruduced by the fix for bug#17212 (in 4.1). It is not
ok to call test_if_skip_sort_order since this function will
alter the execution plan. By contract it is not ok to call
test_if_skip_sort_order in this context.
This bug appears only in the case when the optimizer has chosen
an index for accessing a particular table but finds a covering
index that enables it to skip ORDER BY. This happens in
test_if_skip_sort_order.
When merging views into the enclosing statement
the ORDER BY clause of the view is merged to the
parent's ORDER BY clause.
However when the VIEW is merged into an UNION
branch the ORDER BY should be ignored.
Use of ORDER BY for individual SELECT statements
implies nothing about the order in which the rows
appear in the final result because UNION by default
produces unordered set of rows.
Fixed by ignoring the ORDER BY clause from the merge
view when expanded in an UNION branch.
They can drop table after table names list creation and before table opening.
We open non existing table and get ER_NO_SUCH_TABLE error.
In this case we do not store the record into I_S table and clear error.
conditions when executing an equijoin query with WHERE condition
containing a subquery predicate of the form join_attr NOT IN (SELECT ...).
To resolve a problem of the correct evaluation of the expression
attr NOT IN (SELECT ...)
an array of guards is created to make it possible to filter out some
predicates of the EXISTS subquery into which the original subquery
predicate is transformed, in the cases when a takes the NULL value.
If attr is defined as a field that cannot be NULL than such an array
is not needed and is not created.
However if the field a occurred also an an equijoin predicate t2.a=t1.b
and table t1 is accessed before table t2 then it may happen that the
the EXISTS subquery is pushed down to the condition evaluated just after
table t1 has been accessed. In this case any occurrence of t2.a is
substituted for t1.b. When t1.b takes the value of NULL an attempt is
made to turn on the corresponding guard. This action caused a crash as
no guard array had been created.
Now the code of Item_in_subselect::set_cond_guard_var checks that the guard
array has been created before setting a guard variable on. Otherwise the
method does nothing. It cannot results in returning a row that could be
rejected as the condition t2.a=t1.b will be checked later anyway.
The Item_outer_ref class based on the Item_direct_ref class was always used
to represent an outer field. But if the outer select is a grouping one and the
outer field isn't under an aggregate function which is aggregated in that
outer select an Item_ref object should be used to represent such a field.
If the outer select in which the outer field is resolved isn't grouping then
the Item_field class should be used to represent such a field.
This logic also should be used for an outer field resolved through its alias
name.
Now the Item_field::fix_outer_field() uses Item_outer_field objects to
represent aliased and non-aliased outer fields for grouping outer selects
only.
Now the fix_inner_refs() function chooses which class to use to access outer
field - the Item_ref or the Item_direct_ref. An object of the chosen class
substitutes the original field in the Item_outer_ref object.
The direct_ref and the found_in_select_list fields were added to the
Item_outer_ref class.
Support of views wasn't implemented for the TRUNCATE statement.
Now TRUNCATE on views has the same semantics as DELETE FROM view:
mysql_truncate() checks whether the table is a view and falls back
to delete if so.
In order to initialize properly the LEX::updatable for a view
st_lex::can_use_merged() now allows usage of merged views for the
TRUNCATE statement.
