Remove all instances of lazy subquery optimization after MWL#89 is complete.
Even after MWL#89, there are certain cases when subquery predicates are
executed without prior optimization. This may result in bugs as well as
high optimization/explain cost. In addition having a mixed subquery
optimization approach results in a more complex architecture and higher
degree of coupling between different query processing phases.
The goal of this task is to investigate all remaining cases of lazy
subquery optimization, and whenever possible change each such case
to utilize the general approach of MWL#89.
Currently known remaining cases:
- sql_select.cc:remove_eq_cond calls cond->const_item() without
checking if cond is expensive.
Dependency created: WL#89 now depends on WL#168