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112 lines
3.0 KiB
C++
112 lines
3.0 KiB
C++
/*
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Copyright (c) 2010, 2011, Monty Program Ab
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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#ifndef SQL_EXPRESSION_CACHE_INCLUDED
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#define SQL_EXPRESSION_CACHE_INCLUDED
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#include "sql_select.h"
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/**
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Interface for expression cache
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@note
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Parameters of an expression cache interface are set on the creation of the
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cache. They are passed when a cache object of the implementation class is
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constructed. That's why they are not visible in this interface.
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*/
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extern ulong subquery_cache_miss, subquery_cache_hit;
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class Expression_cache :public Sql_alloc
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{
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public:
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enum result {ERROR, HIT, MISS};
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Expression_cache(){};
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virtual ~Expression_cache() {};
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/**
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Shall check the presence of expression value in the cache for a given
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set of values of the expression parameters. Return the result of the
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expression if it's found in the cache.
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*/
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virtual result check_value(Item **value)= 0;
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/**
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Shall put the value of an expression for given set of its parameters
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into the expression cache
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*/
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virtual my_bool put_value(Item *value)= 0;
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/**
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Print cache parameters
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*/
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virtual void print(String *str, enum_query_type query_type)= 0;
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/**
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Is this cache initialized
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*/
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virtual bool is_inited()= 0;
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/**
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Initialize this cache
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*/
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virtual void init()= 0;
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};
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struct st_table_ref;
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struct st_join_table;
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class Item_field;
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/**
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Implementation of expression cache over a temporary table
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*/
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class Expression_cache_tmptable :public Expression_cache
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{
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public:
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Expression_cache_tmptable(THD *thd, List<Item> &dependants, Item *value);
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virtual ~Expression_cache_tmptable();
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virtual result check_value(Item **value);
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virtual my_bool put_value(Item *value);
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void print(String *str, enum_query_type query_type);
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bool is_inited() { return inited; };
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void init();
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private:
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void disable_cache();
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/* tmp table parameters */
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TMP_TABLE_PARAM cache_table_param;
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/* temporary table to store this cache */
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TABLE *cache_table;
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/* Thread handle for the temporary table */
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THD *table_thd;
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/* TABLE_REF for index lookup */
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struct st_table_ref ref;
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/* Cached result */
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Item_field *cached_result;
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/* List of parameter items */
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List<Item> &items;
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/* Value Item example */
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Item *val;
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/* hit/miss counters */
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uint hit, miss;
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/* Set on if the object has been succesfully initialized with init() */
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bool inited;
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};
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#endif /* SQL_EXPRESSION_CACHE_INCLUDED */
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