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c9259f166b
The MIN/MAX optimizer code from the function opt_sum_query erroneously did not take into account conjunctive conditions that did not depend on any table, yet were not identified as constant items. These could be items containing rand() or PS/SP parameters. These items are supposed to be evaluated at the execution phase. That's why if such conditions can be extracted from the WHERE condition the MIN/MAX optimization is not applied as currently it is always done at the optimization phase. (In 5.3 expensive subqueries are also evaluated only at the execution phase. So, if a constant condition with such subquery can be extracted from the WHERE clause the MIN/MAX optimization should not be applied in 5.3.) IF an IN/ALL/SOME predicate with a constant left part is transformed into an EXISTS subquery the resulting subquery should not be considered uncacheable if the right part of the predicate is not uncacheable. Backported the function dbug_print_item() from 5.3. The function is used only for debugging.