name : sql_expression_cache.h /* Copyright (c) 2010, 2011, Monty Program Ab This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */ #ifndef SQL_EXPRESSION_CACHE_INCLUDED #define SQL_EXPRESSION_CACHE_INCLUDED #include "sql_select.h" /** Interface for expression cache @note Parameters of an expression cache interface are set on the creation of the cache. They are passed when a cache object of the implementation class is constructed. That's why they are not visible in this interface. */ extern ulong subquery_cache_miss, subquery_cache_hit; class Expression_cache :public Sql_alloc { public: enum result {ERROR, HIT, MISS}; Expression_cache()= default; virtual ~Expression_cache() = default; /** Shall check the presence of expression value in the cache for a given set of values of the expression parameters. Return the result of the expression if it's found in the cache. */ virtual result check_value(Item **value)= 0; /** Shall put the value of an expression for given set of its parameters into the expression cache */ virtual my_bool put_value(Item *value)= 0; /** Print cache parameters */ virtual void print(String *str, enum_query_type query_type)= 0; /** Is this cache initialized */ virtual bool is_inited()= 0; /** Initialize this cache */ virtual void init()= 0; /** Save this object's statistics into Expression_cache_tracker object */ virtual void update_tracker()= 0; }; struct st_table_ref; struct st_join_table; class Item_field; class Expression_cache_tracker :public Sql_alloc { public: enum expr_cache_state {UNINITED, STOPPED, OK}; Expression_cache_tracker(Expression_cache *c) : cache(c), hit(0), miss(0), state(UNINITED) {} private: // This can be NULL if the cache is already deleted Expression_cache *cache; public: ulong hit, miss; enum expr_cache_state state; static const char* state_str[3]; void set(ulong h, ulong m, enum expr_cache_state s) {hit= h; miss= m; state= s;} void detach_from_cache() { cache= NULL; } void fetch_current_stats() { if (cache) cache->update_tracker(); } }; /** Implementation of expression cache over a temporary table */ class Expression_cache_tmptable :public Expression_cache { public: Expression_cache_tmptable(THD *thd, List<Item> &dependants, Item *value); virtual ~Expression_cache_tmptable(); result check_value(Item **value) override; my_bool put_value(Item *value) override; void print(String *str, enum_query_type query_type) override; bool is_inited() override { return inited; }; void init() override; void set_tracker(Expression_cache_tracker *st) { tracker= st; update_tracker(); } void update_tracker() override { if (tracker) { tracker->set(hit, miss, (inited ? (cache_table ? Expression_cache_tracker::OK : Expression_cache_tracker::STOPPED) : Expression_cache_tracker::UNINITED)); } } private: void disable_cache(); /* tmp table parameters */ TMP_TABLE_PARAM cache_table_param; /* temporary table to store this cache */ TABLE *cache_table; /* Thread handle for the temporary table */ THD *table_thd; /* EXPALIN/ANALYZE statistics */ Expression_cache_tracker *tracker; /* TABLE_REF for index lookup */ struct st_table_ref ref; /* Cached result */ Item_field *cached_result; /* List of parameter items */ List<Item> &items; /* Value Item example */ Item *val; /* hit/miss counters */ ulong hit, miss; /* Set on if the object has been successfully initialized with init() */ bool inited; }; #endif /* SQL_EXPRESSION_CACHE_INCLUDED */