MDEV-11357 Split Item_cache::get_cache() into virtual methods in Type_handler

This patch:
- Adds a new virtual method Type_handler::Item_get_cache
- Splits moves Item_cache::get_cache() into the new method, every
  "case XXX_RESULT" to the corresponding Type_handler_xxx::Item_get_cache.
- Adds Item::get_cache as a convenience wrapper, to make the caller code
  shorter.
- Changes the last argument of Arg_comparator::cache_converted_constant()
  from Item_result to "const Type_handler *".
- Removes subselect_engine::cmp_type, subselect_engine::res_type,
  subselect_engine::res_field_type and derives subselect_engine
  from Type_handler_hybrid_field_type instead.
- Makes Type_handler_varchar public, as it's now needed as the
  default data type handler for subselect_engine.

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/item_windowfunc.cc b/sql/item_windowfunc.cc
index a13967eaaad..27eeeff6482 100644
--- a/sql/item_windowfunc.cc
+++ b/sql/item_windowfunc.cc
@@ -301,7 +301,7 @@ bool Item_sum_hybrid_simple::add()
 
 void Item_sum_hybrid_simple::setup_hybrid(THD *thd, Item *item)
 {
-  if (!(value= Item_cache::get_cache(thd, item, item->cmp_type())))
+  if (!(value= item->get_cache(thd)))
     return;
   value->setup(thd, item);
   value->store(item);