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.
with window functions. Added the test case for it.
Also allowed to use aliases for set functions in partition and order lists
that are specified in window functions.
Add support for "RANGE n PRECEDING|FOLLOWING" frame bounds.
- n is currently limited to whatever Item and Item_sum_plus/minus
can handle (i.e. no DATETIME intervals).
- Didn't check NULL value handling yet.
Part#2: Fix a couple more issues in rows-type frames.
This also has a code cleanup:
- introduce a separate Frame_rows_current_row_(top,bottom). This is
is a special case which doesn't need its cursor or partition bound check
- Split Frame_n_rows into
= Frame_n_rows_preceding (this one is now much simpler)
= Frame_n_rows_following (simpler and works but may need some work still)
Part#1: Frame_n_rows::next_partition() should not assume that the
current table->record[0] points to the first row in the partition.
Since cursor supports move_to() operation, we dont need this.
- 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.
