When ordering by a column and partitioning by another, we must reset the
peer_tracker for dense_rank, regardless if the value for the order
column changes or not.
Example:
select a, b, dense_rank() over (partition by b order by a)
a | b | dense_rank
----------------------
1 | p1 | 1
2 | p1 | 2
2 | p2 | 1 // Here, without this fix we returned 0.
2 | p2 | 2 // And 1 here.
The bug was caused by a weird behaviour in test_if_group_changed, not
returning true when testing for the first time after initializing
the Cached_item list.
- When window functions are present, JOIN::simple_order should be set
to FALSE. (Otherwise, the optimizer may attempt to do a "pre-sorting"
on the first join_tab. Which can work in some cases, but generally
isn't)
- filesort tries to only read table fields that it requires. Window
function requires its temp.table field. In order to pass this info
to filesort, added an implementation of Item_window_func::
register_field_in_read_map.
- Make Item_XXX::cleanup() clean List<Cached_item> orderby_fields.
(Items survive across PS re-executions. Cached_item don't, because
they keep pointers to fix_field'ed items, etc)
- Move List<Cached_item> out into Group_bound_tracker.
Item_func_or_sum.
Implemented method update_used_tables for class Item_findow_func.
Added the flag Item::with_window_func.
Made sure that window functions could be used only in SELECT list
and ORDER BY clause.
Added test cases that checked different illegal placements of
window functions.
1. Item_windowfunc must check the nullness of the field if it returns the
value from the result_field.
2. The decimal value must come from the window_func instead of the
result_field when not fetching values from the result_field.
Added a more extensive test case that highlights if these bugs occur.
The 2 select statements check behaviour for decimal and real typed
fields respectively.
Query result had 0 where it should have had NULLs:
- Make Item_window_func::val* functions honor NULL-handling conventions:
1. set null_value to indicate whether we've returned a NULL value
2. val_str and val_decimal should return NULL pointer when they're
returning SQL NULL value.
Fix assertion failure when sending results to network.
- The assert was due to window func returing SQL NULL despite having
maybe_null=false
- Fixed by settting Item_window_func::maybe_null correctly in fix_fields
- Item_sum_count::remove() should check if the argument's value is NULL.
- Window Function item must have its Item_window_func::split_sum_func
called,
- and it must call split_sum_func for aggregate's arguments (see the
comment near Item_window_func::split_sum_func for explanation why)
- Add temporary code: clone_read_record() clones READ_RECORD structure,
as long as it is used for reading filesort() result that fits into
memory.
- Add frame bounds for ROWS-type frames. ROWS n PRECEDING|FOLLOWING,
ROWS UNBOUNDED PRECEDING|FOLLOWING, CURRENT ROW are supported.
- Add Item_sum_count::remove() which allows "streaming" computation
of COUNT() over a moving frame.
