This is another attempt to fix the bug mdev-12992.
This patch introduces st_select_lex::context_analysis_place for
the place in SELECT where context analysis is currently performed.
It's similar to st_select_lex::parsing_place, but it is used at
the preparation stage.
Due to this bug many queries that contained a window function
with MIN/MAX aggregation returned wrong results.
Calculation of a MIN/MAX aggregate function uses cache objects
and a comparator object that are created and set up in
Item_sum_hybrid::fix_fields () by a call of Item_sum_hybrid::setup_hybrid().
The latter binds the objects to the first argument of the
MIN/MAX function. Meanwhile window function perform aggregation
over fields of a temporary table. So binding must be done rather to
these fields. The earliest moment when setup the objects used in
MIN/max functions can be done is after all calls of the method
split_sum_func().
This patch introduces this late setup, but only for aggregate
functions used in window functions.
Probably it makes sense to use this late setup for all MIN/MAX
objects.
There was no implementation of the virtual method print()
for the Item_window_func class. As a result for a view
containing window function an invalid view definition could
be written in the frm file. When a query that refers to
this view was executed a syntax error was reported.
Refactour out (into a copy for now) the logic of Item_sum_hybrid, to
allow for multiple arguments. It does not contain the comparator
members. The result is the class Item_sum_hybrid_simple.
LEAD and LAG make use of this Item to store previous rows in a chache.
It also helps in specifying the field type. Currently LEAD/LAG do not
support default values.
NTH_VALUE behaves identical to LEAD and LAG, except that the starting
position cursor is placed on the top of the frame instead of the current
row.
Perform only one table scan for each window function present. We do this
by keeping keeping cursors for each window function frame bound and
running them for each function for every row.
