The bitmap of used tables must be evaluated for the select list of every
materialized derived table / view and saved in a dedicated field.
This is also applied to materialized subqueries.
Bug#11766642: crash in Item_field::register_field_in_read_map
with view
(Former 59793)
Prior to the refactoring in this patch, Item_cond_xor behaved
partially as an Item_cond and partially as an Item_func. The
reasoning behind this was that XOR is currently not optimized
(thus should be Item_func instead of Item_cond), but it was
planned optimize it in the future (thus, made Item_cond anyway
to ease optimization later).
Even though Item_cond inherits from Item_func, there are
differences between these two. One difference is that the
arguments are stored differently. Item_cond stores them in a
list while Item_func store them in an args[].
BUG no 45221 was caused by Item_cond_xor storing arguments in
the list while users of the objects would look for them in
args[]. The fix back then was to store the arguments in both
locations.
In this bug, Item_cond_xor initially gets two Item_field
arguments. These are stored in the list inherited from
Item_cond and in args[] inherited from Item_func. During
resolution, find_field_in_view() replaces the Item_fields
stored in the list with Item_direct_view_refs, but args[]
still points to the unresolved Item_fields. This shows that
the fix for 45221 was incorrect.
The refactoring performed in this patch removes the confusion
by making the XOR item an Item_func period. A neg_transformer()
is also implemented for Item_func_xor to improve performance
when negating XOR expressions. An XOR is negated by negating
one of the operands.
The cause of the crash is sj_nest->sj_subq_pred->unit->first_select()->item_list
contains "stale" items for the second execution. By "stale" I mean that they have
item->fixed==FALSE, and they are Item_field object instead of Item_direct_view_ref.
The solution is to use sj_nest->sj_subq_pred->unit->first_select()->ref_pointer_array.
Surprisingly, that array contains items that are ok.
Oracle team has introduced and is using NESTED_JOIN::sj_inner_exprs, but we go without that
and always copy the ref_pointer_array.
Missing initialization of the bitmap not_null_tables_cache to 0
in the function Item_func::eval_not_null_tables caused this bug.
This function is called indirectly from the function
SELECT_LEX::update_used_tables after merging mergeable views and
derived tables into the main query. The leaf tables of resulting
query may change their bitmap numbers after this merge. That's why
the not_null_tables_cache bitmaps must be updated. Due to the bug
mentioned above the result of the re-evaluation of the
not_null_tables_cache turned out to be incorrect in some cases.
This could trigger an invalid conversion of outer joins into
inner joins leading to invalid query result sets.
Also removed an implicit conversion from int to bool in the function
SELECT_LEX::update_used_tables.
The value of THD::used tables should be re-evaluated after merges
of views and derived tables into the main query.
Now it's done in the function SELECT_LEX::update_used_tables.
The re-evaluation of the 'used_table' bitmaps for the items
in HAVING, GROUP BY and ORDER BY clauses has been added as well.
The bug was caused by an incorrect code of the function
Item_direct_view_ref::replace_equal_field introduced in the
patch for bugs 717577, 724942. The function erroneously
returned the wrapped field instead of the Item_direct_view_ref
object itself in the cases when no replacement happened.
The bug masked two other minor bugs that could result in not
quite correct output of the EXPLAIN command for some queries.
They were fixed in the patch as well.
- Set the default
- Adjust the testcases so that 'new' tests are run with optimizations turned on.
- Pull out relevant tests from "irrelevant" tests and run them with optimizations on.
- Run range.test and innodb.test with both mrr=on and mrr=off
The offending query returns a wrong result set because the optimizer
erroneously eliminated the where condition evaluated it to TRUE.
The cause of this wrong transformation was that the flag maybe_null
for an inner table of the outer join was not set to TRUE after the
table had replaced the wrapping view.
Now the function SELECT_LEX::update_used_tables resets the value
of the maybe_null flag for each leaf table of the query after all
merges of views have been done.
Analysis:
This bug is yet another incarnation of the generic problem
where optimization of the outer query triggers evaluation
of a subquery, and this evaluation performs a destructive
change to the subquery plan. Specifically a temp table is
created for the DISTINCT operation that replaces the
original subquery table. Later, select_describe() attempts
to print the table name, however, there is no corresponding
TABLE_LIST object to the internal temp table, so we get a
crash. Execution works fine because it is not interested in
the corresponding TABLE_LIST object (or its name).
Solution:
Similar to other such bugs, block the evaluation of expensive
Items in convert_const_to_int().
The function generate_derived_keys_for_table incorrectly handled
the cases when a materialized view or derived table could be accessed
by different keys on the same fields if these keys depended on the
same tables.
The bug lp:798213 exposes a design flaw in --innodb-release-locks-early.
It does not work with InnoDB crash recovery, so it breaks transactional
integrety. So remove the feature.
