find_contained_subqueries.h

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#ifndef SQL_JOIN_OPTIMIZER_FIND_CONTAINED_SUBQUERIES
#define SQL_JOIN_OPTIMIZER_FIND_CONTAINED_SUBQUERIES 1
 
#include "sql/item_subselect.h"
#include "sql/join_optimizer/access_path.h"
#include "sql/sql_const.h"
#include "sql/sql_lex.h"
 
class Item;
class THD;
class Item;
class Query_block;
 
/***
Find out which subqueries are contained in this predicate, if any.
(This only counts IN/ALL/ANY/comparison_operator subqueries, ie.,
those that we consider materializing and have not converted to
semijoins.) Note that calling this repeatedly can be quite expensive,
so many callers will want to cache this information.
 
Func should be on the form void func(ContainedSubquery), or something
compatible.
 
@param condition the root of the predicate.
@param outer_query_block the Query_block to which 'condition' belongs.
@param func a function that is called for each contained subquery.
*/
template <class Func>
void FindContainedSubqueries(Item *condition,
                             const Query_block *outer_query_block,
                             Func &&func) {
  WalkItem(condition, enum_walk::POSTFIX,
           [outer_query_block, &func](Item *item) {
             std::optional<ContainedSubquery> subquery =
                 item->get_contained_subquery(outer_query_block);
 
             if (subquery.has_value()) {
               func(subquery.value());
             }
             return false;
           });
}
 
#endif  // SQL_JOIN_OPTIMIZER_FIND_CONTAINED_SUBQUERIES