Calling List<Cached_item>::delete_elements for the same list twice
caused a crash of the server in the function JOIN::cleaunup.
Ensured that delete_elements() in JOIN::cleanup would be called only once.
Range scan in descending order for c <= <col> <= c type of
ranges was ignoring the DESC flag.
However some engines like InnoDB have the primary key parts
as a suffix for every secondary key.
When such primary key suffix is used for ordering ignoring
the DESC is not valid.
But we generally would like to do this because it's faster.
Fixed by performing only reverse scan if the primary key is used.
Removed some dead code in the process.
Range scan in descending order for c <= <col> <= c type of
ranges was ignoring the DESC flag.
However some engines like InnoDB have the primary key parts
as a suffix for every secondary key.
When such primary key suffix is used for ordering ignoring
the DESC is not valid.
But we generally would like to do this because it's faster.
Fixed by performing only reverse scan if the primary key is used.
Removed some dead code in the process.
- In QUICK_INDEX_MERGE_SELECT::read_keys_and_merge: when we got table->sort from Unique,
tell init_read_record() not to use rr_from_cache() because a) rowids are already sorted
and b) it might be that the the data is used by filesort(), which will need record rowids
(which rr_from_cache() cannot provide).
- Fully de-initialize the table->sort read in QUICK_INDEX_MERGE_SELECT::get_next(). This fixes BUG#35477.
(bk trigger: file as fix for BUG#35478).
InnoDB table, where all selected columns
belong to the same unique index key, returns
incorrect results
Server executes some queries via QUICK_GROUP_MIN_MAX_SELECT
(MIN/MAX optimization for queries with GROUP BY or DISTINCT
clause) and that optimization implies loose index scan, so all
grouping is done by the QUICK_GROUP_MIN_MAX_SELECT::get_next
method.
The server does not set the precomputed_group_by flag for some
QUICK_GROUP_MIN_MAX_SELECT queries and duplicates grouping by
call to the end_send_group function.
Fix: when the test_if_skip_sort_order function selects loose
index scan as a best way to satisfy an ORDER BY/GROUP BY type
of query, the precomputed_group_by flag has been set to use
end_send/end_write functions instead of end_send_group/
end_write_group functions.
with dependent subqueries
An IN subquery is executed on EXPLAIN when it's not correlated.
If the subquery required a temporary table for its execution
not all the internal structures were restored from pointing to
the items of the temporary table to point back to the items of
the subquery.
Fixed by restoring the ref array when a temp tables were used in
executing the IN subquery during EXPLAIN EXTENDED.
- Disable the "prefer full scan on clustered primary key over full scan
of any secondary key" rule introduced by BUG#35850.
- Update test results accordingly
(bk trigger: file this for BUG#35850)
The function test_if_skip_sort_order ignored any covering index used for ref
access of a table in a query with ORDER BY if this index was incompatible
with the ORDER BY list and there was another covering index compatible with
this list.
As a result sub-optimal execution plans were chosen for some queries with
ORDER BY clause.
impossible WHERE/HAVING clause
(subselect_single_select_engine::exec).
Allocation and initialization of joined table list t1, t2... of
subqueries like:
NOT IN (SELECT ... FROM t1,t2,... WHERE 0)
is optimized out, however server tries to traverse this list.
The code for executing indexed ORDER BY was not setting all the
internal fields correctly when selecting to execute ORDER BY over
and index.
Fixed by change the access method to one that will use the
quick indexed access if one is selected while selecting indexed
ORDER BY.
Mixing aggregate functions and non-grouping columns is not allowed in the
ONLY_FULL_GROUP_BY mode. However in some cases the error wasn't thrown because
of insufficient check.
In order to check more thoroughly the new algorithm employs a list of outer
fields used in a sum function and a SELECT_LEX::full_group_by_flag.
Each non-outer field checked to find out whether it's aggregated or not and
the current select is marked accordingly.
All outer fields that are used under an aggregate function are added to the
Item_sum::outer_fields list and later checked by the Item_sum::check_sum_func
function.
View definition as SELECT ... FROM DUAL WHERE ... has
valid syntax, but use of such view in SELECT or
SHOW CREATE VIEW syntax causes unexpected syntax error.
Server omits FROM DUAL clause when storing view body
string in a .frm file for further evaluation.
However, syntax of SELECT-witout-FROM query is more
restrictive than SELECT FROM DUAL syntax, and doesn't
allow the WHERE clause.
NOTE: this syntax difference is not documented.
View registration procedure has been modified to
preserve original structure of view's body.
The bug is a regression introduced in 5.1 by the patch for bug28404.
Under some circumstances test_if_skip_sort_order() could leave some
data structures in an inconsistent state so that some parts of code
could assume the selected execution strategy for GROUP BY/DISTINCT as
a loose index scan (e.g. JOIN_TAB::is_using_loose_index_scan()), while
the actual strategy chosen was an ordered index scan, which led to
wrong data being returned.
Fixed test_if_skip_sort_order() so that when changing the type for a
join table, select->quick is reset not only for EXPLAIN, but for the
actual join execution as well, to not confuse code that depends on its
value to determine the chosen GROUP BY/DISTINCT strategy.
- Apply Eric Bergen's patch: in join_read_always_key(), move ha_index_init() call
to before the late NULLs filtering code.
- Backport function comments from 6.0.
and Item_direct_ref constructor calls.
Order of ref->field_name and ref->table_name arguments
is of Item_ref and Item_direct_ref in the fix_inner_refs
function is inverted.
between 5.0 and 5.1.
The problem was that in the patch for Bug#11986 it was decided
to store original query in UTF8 encoding for the INFORMATION_SCHEMA.
This approach however turned out to be quite difficult to implement
properly. The main problem is to preserve the same IS-output after
dump/restore.
So, the fix is to rollback to the previous functionality, but also
to fix it to support multi-character-set-queries properly. The idea
is to generate INFORMATION_SCHEMA-query from the item-tree after
parsing view declaration. The IS-query should:
- be completely in UTF8;
- not contain character set introducers.
For more information, see WL4052.
Problem is not about intervals and doesn't actually cause 'full table scan'.
We have an optimization for DISTINCT when we have
'DISTINCT field_from_first_join_table' we don't need to read all the
rows from the JOIN-ed table if we found one conforming row.
It stopped working in 5.0 as we return NESTED_LOOP_OK if we came upon
that case in the evaluate_join_record() and that doesn't break the
recordreading loop in sub_select().
Fixed by returning NESTED_LOOP_NO_MORE_ROWS in this case.
Two disjuncts containing equalities of the form key=const1 and key=const2 can
be merged into one if const1 is equal to const2. To check it the common
collation of the constants were used rather than the collation of the field key.
For example when the default collation of the constants was cases insensitive
while the collation of the field was case sensitive, then two or-ed equality
predicates key='b' and key='B' incorrectly were merged into one f='b'. As a
result ref access was used instead of range access and wrong result sets were
returned in many cases.
Fixed the problem by comparing constant in the or-ed predicate with collation of
the key field.
