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✏️ Editing: sql_cache.h

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 St, Fifth Floor, Boston, MA 02110-1335  USA */

#ifndef _SQL_CACHE_H
#define _SQL_CACHE_H

#include "hash.h"
#include "my_base.h"                            /* ha_rows */

class MY_LOCALE;
struct TABLE_LIST;
class Time_zone;
struct LEX;
struct TABLE;
typedef struct st_changed_table_list CHANGED_TABLE_LIST;

/* Query cache */

/*
   Can't create new free memory block if unused memory in block less
   then QUERY_CACHE_MIN_ALLOCATION_UNIT.
   if QUERY_CACHE_MIN_ALLOCATION_UNIT == 0 then
   QUERY_CACHE_MIN_ALLOCATION_UNIT choosed automatically
*/
#define QUERY_CACHE_MIN_ALLOCATION_UNIT		512

/* inittial size of hashes */
#define QUERY_CACHE_DEF_QUERY_HASH_SIZE		1024
#define QUERY_CACHE_DEF_TABLE_HASH_SIZE		1024

/* minimal result data size when data allocated */
#define QUERY_CACHE_MIN_RESULT_DATA_SIZE	(1024*4)

/* 
   start estimation of first result block size only when number of queries
   bigger then: 
*/
#define QUERY_CACHE_MIN_ESTIMATED_QUERIES_NUMBER 3

/* memory bins size spacing (see at Query_cache::init_cache (sql_cache.cc)) */
#define QUERY_CACHE_MEM_BIN_FIRST_STEP_PWR2	4
#define QUERY_CACHE_MEM_BIN_STEP_PWR2		2
#define QUERY_CACHE_MEM_BIN_PARTS_INC		1
#define QUERY_CACHE_MEM_BIN_PARTS_MUL		1.2
#define QUERY_CACHE_MEM_BIN_SPC_LIM_PWR2	3

/* how many free blocks check when finding most suitable before other 'end'
   of list of free blocks */
#define QUERY_CACHE_MEM_BIN_TRY                 5

/* packing parameters */
#define QUERY_CACHE_PACK_ITERATION		2
#define QUERY_CACHE_PACK_LIMIT			(512*1024L)

#define TABLE_COUNTER_TYPE uint

struct Query_cache_block;
struct Query_cache_block_table;
struct Query_cache_table;
struct Query_cache_query;
struct Query_cache_result;
class Query_cache;
struct Query_cache_tls;
struct LEX;
class THD;

typedef my_bool (*qc_engine_callback)(THD *thd, const char *table_key,
                                      uint key_length,
                                      ulonglong *engine_data);

/**
  This class represents a node in the linked chain of queries
  belonging to one table.

@note The root of this linked list is not a query-type block, but the table-
        type block which all queries has in common.
*/
struct Query_cache_block_table
{
  Query_cache_block_table() = default;                /* Remove gcc warning */

/**
    This node holds a position in a static table list belonging
    to the associated query (base 0).
  */
  TABLE_COUNTER_TYPE n;

/**
    Pointers to the next and previous node, linking all queries with 
    a common table.
  */
  Query_cache_block_table *next, *prev;

/**
    A pointer to the table-type block which all
    linked queries has in common.
  */
  Query_cache_table *parent;

/**
    A method to calculate the address of the query cache block
    owning this node. The purpose of this calculation is to 
    make it easier to move the query cache block without having
    to modify all the pointer addresses.
  */
  inline Query_cache_block *block();
};

struct Query_cache_block
{
  Query_cache_block() = default;                      /* Remove gcc warning */
  enum block_type {FREE, QUERY, RESULT, RES_CONT, RES_BEG,
		   RES_INCOMPLETE, TABLE, INCOMPLETE};

size_t length;					// length of all block
  size_t used;					// length of data
  /*
    Not used **pprev, **prev because really needed access to pervious block:
    *pprev to join free blocks
    *prev to access to opposite side of list in cyclic sorted list
  */
  Query_cache_block *pnext,*pprev,		// physical next/previous block
		    *next,*prev;		// logical next/previous block
  block_type type;
  TABLE_COUNTER_TYPE n_tables;			// number of tables in query

inline bool is_free(void) { return type == FREE; }
  void init(size_t length);
  void destroy();
  uint headers_len() const;
  uchar* data(void) const;
  Query_cache_query *query();
  Query_cache_table *table();
  Query_cache_result *result();
  Query_cache_block_table *table(TABLE_COUNTER_TYPE n);
};

struct Query_cache_query
{
  ulonglong limit_found_rows;
  mysql_rwlock_t lock;
  Query_cache_block *res;
  Query_cache_tls *wri;
  size_t len;
  unsigned int last_pkt_nr;
  uint8 tbls_type;
  uint8 ready;
  ulonglong hit_count;

Query_cache_query() = default;                      /* Remove gcc warning */
  inline void init_n_lock();
  void unlock_n_destroy();
  inline ulonglong found_rows()		   { return limit_found_rows; }
  inline void found_rows(ulonglong rows)   { limit_found_rows= rows; }
  inline Query_cache_block *result()	   { return res; }
  inline void result(Query_cache_block *p) { res= p; }
  inline Query_cache_tls *writer()	   { return wri; }
  inline void writer(Query_cache_tls *p)   { wri= p; }
  inline uint8 tables_type()               { return tbls_type; }
  inline void tables_type(uint8 type)      { tbls_type= type; }
  inline size_t length()			   { return len; }
  inline size_t add(size_t packet_len)	   { return(len+= packet_len); }
  inline void length(size_t length_arg)	   { len= length_arg; }
  inline uchar* query()
  {
    return (((uchar*)this) + ALIGN_SIZE(sizeof(Query_cache_query)));
  }
  /**
    following used to check if result ready in plugin without
    locking rw_lock of the query.
  */
  inline void set_results_ready()          { ready= 1; }
  inline bool is_results_ready()           { return ready; }
  inline void increment_hits() { hit_count++; }
  inline ulonglong hits() { return hit_count; }
  void lock_writing();
  void lock_reading();
  bool try_lock_writing();
  void unlock_writing();
  void unlock_reading();
};

struct Query_cache_table
{
  Query_cache_table() = default;                      /* Remove gcc warning */
  char *tbl;
  uint32 key_len;
  uint8 suffix_len;                          /* For partitioned tables */
  uint8 table_type;
  /* unique for every engine reference */
  qc_engine_callback callback_func;
  /* data need by some engines */
  ulonglong engine_data_buff;

/**
    The number of queries depending of this table.
  */
  int32 m_cached_query_count;
  /**
    If table included in the table hash to be found by other queries
  */
  my_bool hashed;

inline char *db()			     { return (char *) data(); }
  inline char *table()			     { return tbl; }
  inline void table(char *table_arg)	     { tbl= table_arg; }
  inline uint32 key_length()                 { return key_len; }
  inline void key_length(uint32 len)         { key_len= len; }
  inline uint8 suffix_length()               { return suffix_len; }
  inline void suffix_length(uint8 len)       { suffix_len= len; }
  inline uint8 type()                        { return table_type; }
  inline void type(uint8 t)                  { table_type= t; }
  inline qc_engine_callback callback()       { return callback_func; }
  inline void callback(qc_engine_callback fn){ callback_func= fn; }
  inline ulonglong engine_data()             { return engine_data_buff; }
  inline void engine_data(ulonglong data_arg){ engine_data_buff= data_arg; }
  inline my_bool is_hashed()                 { return hashed; }
  inline void set_hashed(my_bool hash)       { hashed= hash; }
  inline uchar* data()
  {
    return (uchar*)(((uchar*)this)+
		  ALIGN_SIZE(sizeof(Query_cache_table)));
  }
};

struct Query_cache_result
{
  Query_cache_result() = default;                     /* Remove gcc warning */
  Query_cache_block *query;

inline uchar* data()
  {
    return (uchar*)(((uchar*) this)+
		  ALIGN_SIZE(sizeof(Query_cache_result)));
  }
  /* data_continue (if not whole packet contained by this block) */
  inline Query_cache_block *parent()		  { return query; }
  inline void parent (Query_cache_block *p)	  { query=p; }
};

extern "C"
{
  const uchar *query_cache_query_get_key(const void *record, size_t *length,
                                         my_bool);
  const uchar *query_cache_table_get_key(const void *record, size_t *length,
                                         my_bool);
}
extern "C" void query_cache_invalidate_by_MyISAM_filename(const char* filename);

struct Query_cache_memory_bin
{
  Query_cache_memory_bin() = default;                 /* Remove gcc warning */
#ifndef DBUG_OFF
  size_t size;
#endif
  uint number;
  Query_cache_block *free_blocks;

inline void init(size_t size_arg)
  {
#ifndef DBUG_OFF
    size = size_arg;
#endif
    number = 0;
    free_blocks = 0;
  }
};

struct Query_cache_memory_bin_step
{
  Query_cache_memory_bin_step() = default;            /* Remove gcc warning */
  size_t size;
  size_t increment;
  size_t idx;
  inline void init(size_t size_arg, size_t idx_arg, size_t increment_arg)
  {
    size = size_arg;
    idx = idx_arg;
    increment = increment_arg;
  }
};

class Query_cache
{
public:
  /* Info */
  size_t query_cache_size, query_cache_limit;
  /* statistics */
  size_t free_memory, queries_in_cache, hits, inserts, refused,
    free_memory_blocks, total_blocks, lowmem_prunes;

private:
#ifndef DBUG_OFF
  my_thread_id m_cache_lock_thread_id;
#endif
  mysql_cond_t COND_cache_status_changed;
  uint m_requests_in_progress;
  enum Cache_lock_status { UNLOCKED, LOCKED_NO_WAIT, LOCKED };
  Cache_lock_status m_cache_lock_status;
  enum Cache_staus {OK, DISABLE_REQUEST, DISABLED};
  Cache_staus m_cache_status;

void free_query_internal(Query_cache_block *point);
  void invalidate_table_internal(uchar *key, size_t key_length);

protected:
  /*
    The following mutex is locked when searching or changing global
    query, tables lists or hashes. When we are operating inside the
    query structure we locked an internal query block mutex.
    LOCK SEQUENCE (to prevent deadlocks):
      1. structure_guard_mutex
      2. query block (for operation inside query (query block/results))

Thread doing cache flush releases the mutex once it sets
    m_cache_lock_status flag, so other threads may bypass the cache as
    if it is disabled, not waiting for reset to finish.  The exception
    is other threads that were going to do cache flush---they'll wait
    till the end of a flush operation.
  */
  mysql_mutex_t structure_guard_mutex;
  size_t additional_data_size;
  uchar *cache;					// cache memory
  Query_cache_block *first_block;		// physical location block list
  Query_cache_block *queries_blocks;		// query list (LIFO)
  Query_cache_block *tables_blocks;

Query_cache_memory_bin *bins;			// free block lists
  Query_cache_memory_bin_step *steps;		// bins spacing info
  HASH queries, tables;
  /* options */
  size_t min_allocation_unit, min_result_data_size;
  uint def_query_hash_size, def_table_hash_size;
  
  size_t mem_bin_num, mem_bin_steps;		// See at init_cache & find_bin

bool initialized;

/* Exclude/include from cyclic double linked list */
  static void double_linked_list_exclude(Query_cache_block *point,
					 Query_cache_block **list_pointer);
  static void double_linked_list_simple_include(Query_cache_block *point,
						Query_cache_block **
						list_pointer);
  static void double_linked_list_join(Query_cache_block *head_tail,
				      Query_cache_block *tail_head);

/* The following functions require that structure_guard_mutex is locked */
  void flush_cache();
  my_bool free_old_query();
  void free_query(Query_cache_block *point);
  my_bool allocate_data_chain(Query_cache_block **result_block,
			      size_t data_len,
			      Query_cache_block *query_block,
			      my_bool first_block);
  void invalidate_table(THD *thd, TABLE_LIST *table);
  void invalidate_table(THD *thd, TABLE *table);
  void invalidate_table(THD *thd, uchar *key, size_t  key_length);
  void invalidate_table(THD *thd, Query_cache_block *table_block);
  void invalidate_query_block_list(Query_cache_block_table *list_root);

TABLE_COUNTER_TYPE
    register_tables_from_list(THD *thd, TABLE_LIST *tables_used,
                              TABLE_COUNTER_TYPE counter,
                              Query_cache_block_table **block_table);
  my_bool register_all_tables(THD *thd, Query_cache_block *block,
			      TABLE_LIST *tables_used,
			      TABLE_COUNTER_TYPE tables);
  void unlink_table(Query_cache_block_table *node);
  Query_cache_block *get_free_block (size_t len, my_bool not_less,
				      size_t min);
  void free_memory_block(Query_cache_block *point);
  void split_block(Query_cache_block *block, size_t len);
  Query_cache_block *join_free_blocks(Query_cache_block *first_block,
				       Query_cache_block *block_in_list);
  my_bool append_next_free_block(Query_cache_block *block,
				 size_t add_size);
  void exclude_from_free_memory_list(Query_cache_block *free_block);
  void insert_into_free_memory_list(Query_cache_block *new_block);
  my_bool move_by_type(uchar **border, Query_cache_block **before,
		       size_t *gap, Query_cache_block *i);
  uint find_bin(size_t size);
  void move_to_query_list_end(Query_cache_block *block);
  void insert_into_free_memory_sorted_list(Query_cache_block *new_block,
					   Query_cache_block **list);
  void pack_cache();
  void relink(Query_cache_block *oblock,
	      Query_cache_block *nblock,
	      Query_cache_block *next,
	      Query_cache_block *prev,
	      Query_cache_block *pnext,
	      Query_cache_block *pprev);
  my_bool join_results(size_t join_limit);

/*
    Following function control structure_guard_mutex
    by themself or don't need structure_guard_mutex
  */
  size_t init_cache();
  void make_disabled();
  void free_cache();
  Query_cache_block *write_block_data(size_t data_len, uchar* data,
				       size_t header_len,
				       Query_cache_block::block_type type,
				       TABLE_COUNTER_TYPE ntab = 0);
  my_bool append_result_data(Query_cache_block **result,
			     size_t data_len, uchar* data,
			     Query_cache_block *parent);
  my_bool write_result_data(Query_cache_block **result,
			    size_t data_len, uchar* data,
			    Query_cache_block *parent,
			    Query_cache_block::block_type
			    type=Query_cache_block::RESULT);
  inline size_t get_min_first_result_data_size();
  inline size_t get_min_append_result_data_size();
  Query_cache_block *allocate_block(size_t len, my_bool not_less,
				     size_t min);
  /*
    If query is cacheable return number tables in query
    (query without tables not cached)
  */
  TABLE_COUNTER_TYPE is_cacheable(THD *thd,
                                  LEX *lex, TABLE_LIST *tables_used,
                                  uint8 *tables_type);
  TABLE_COUNTER_TYPE process_and_count_tables(THD *thd,
                                              TABLE_LIST *tables_used,
                                              uint8 *tables_type);

static my_bool ask_handler_allowance(THD *thd, TABLE_LIST *tables_used);
 public:

Query_cache(size_t query_cache_limit = ULONG_MAX,
	      size_t min_allocation_unit = QUERY_CACHE_MIN_ALLOCATION_UNIT,
	      size_t min_result_data_size = QUERY_CACHE_MIN_RESULT_DATA_SIZE,
	      uint def_query_hash_size = QUERY_CACHE_DEF_QUERY_HASH_SIZE,
	      uint def_table_hash_size = QUERY_CACHE_DEF_TABLE_HASH_SIZE);

inline bool is_disabled(void) { return m_cache_status != OK; }
  inline bool is_disable_in_progress(void)
  { return m_cache_status == DISABLE_REQUEST; }

/* initialize cache (mutex) */
  void init();
  /* resize query cache (return real query size, 0 if disabled) */
  size_t resize(size_t query_cache_size);
  /* set limit on result size */
  inline void result_size_limit(size_t limit){query_cache_limit=limit;}
  /* set minimal result data allocation unit size */
  size_t set_min_res_unit(size_t size);

/* register query in cache */
  void store_query(THD *thd, TABLE_LIST *used_tables);

/*
    Check if the query is in the cache and if this is true send the
    data to client.
  */
  int send_result_to_client(THD *thd, char *query, uint query_length);

/* Remove all queries that uses any of the listed following tables */
  void invalidate(THD *thd, TABLE_LIST *tables_used,
		  my_bool using_transactions);
  void invalidate(THD *thd, CHANGED_TABLE_LIST *tables_used);
  void invalidate_locked_for_write(THD *thd, TABLE_LIST *tables_used);
  void invalidate(THD *thd, TABLE *table, my_bool using_transactions);
  void invalidate(THD *thd, const char *key, size_t key_length,
		  my_bool using_transactions);

/* Remove all queries that uses any of the tables in following database */
  void invalidate(THD *thd, const LEX_CSTRING &db);

/* Remove all queries that uses any of the listed following table */
  void invalidate_by_MyISAM_filename(const char *filename);

void flush();
  void pack(THD *thd,
            size_t join_limit = QUERY_CACHE_PACK_LIMIT,
	    uint iteration_limit = QUERY_CACHE_PACK_ITERATION);

void destroy();

void insert(THD *thd, Query_cache_tls *query_cache_tls,
              const char *packet,
              size_t length,
              unsigned pkt_nr);
  my_bool insert_table(THD *thd, size_t key_len, const char *key,
		       Query_cache_block_table *node,
		       size_t db_length, uint8 suffix_length_arg,
                       uint8 cache_type,
		       qc_engine_callback callback,
		       ulonglong engine_data,
                       my_bool hash);

void end_of_result(THD *thd);
  void abort(THD *thd, Query_cache_tls *query_cache_tls);

/*
    The following functions are only used when debugging
    We don't protect these with ifndef DBUG_OFF to not have to recompile
    everything if we want to add checks of the cache at some places.
  */
  void wreck(uint line, const char *message);
  void bins_dump();
  void cache_dump();
  void queries_dump();
  void tables_dump();
  my_bool check_integrity(bool not_locked);
  my_bool in_list(Query_cache_block * root, Query_cache_block * point,
		  const char *name);
  my_bool in_table_list(Query_cache_block_table * root,
			Query_cache_block_table * point,
			const char *name);
  my_bool in_blocks(Query_cache_block * point);

/* Table key generation */
  static uint filename_2_table_key (char *key, const char *filename,
				    uint32 *db_langth);

enum Cache_try_lock_mode {WAIT, TIMEOUT, TRY};
  bool try_lock(THD *thd, Cache_try_lock_mode mode= WAIT);
  void lock(THD *thd);
  void lock_and_suspend(void);
  void unlock(void);

void disable_query_cache(THD *thd);
};

#ifdef HAVE_QUERY_CACHE
struct Query_cache_query_flags
{
  unsigned int client_long_flag:1;
  unsigned int client_protocol_41:1;
  unsigned int client_extended_metadata:1;
  unsigned int client_depr_eof:1;
  unsigned int protocol_type:2;
  unsigned int more_results_exists:1;
  unsigned int in_trans:1;
  unsigned int autocommit:1;
  unsigned int pkt_nr;
  uint character_set_client_num;
  uint character_set_results_num;
  uint collation_connection_num;
  uint group_concat_max_len;
  ha_rows limit;
  Time_zone *time_zone;
  sql_mode_t sql_mode;
  ulonglong max_sort_length;
  size_t default_week_format;
  size_t div_precision_increment;
  MY_LOCALE *lc_time_names;
};
#define QUERY_CACHE_FLAGS_SIZE sizeof(Query_cache_query_flags)
#define QUERY_CACHE_DB_LENGTH_SIZE 2
#include "sql_cache.h"
#define query_cache_abort(A,B) query_cache.abort(A,B)
#define query_cache_end_of_result(A) query_cache.end_of_result(A)
#define query_cache_store_query(A, B) query_cache.store_query(A, B)
#define query_cache_destroy() query_cache.destroy()
#define query_cache_result_size_limit(A) query_cache.result_size_limit(A)
#define query_cache_init() query_cache.init()
#define query_cache_resize(A) query_cache.resize(A)
#define query_cache_set_min_res_unit(A) query_cache.set_min_res_unit(A)
#define query_cache_invalidate3(A, B, C) query_cache.invalidate(A, B, C)
#define query_cache_invalidate1(A, B) query_cache.invalidate(A, B)
#define query_cache_send_result_to_client(A, B, C) \
  query_cache.send_result_to_client(A, B, C)
#define query_cache_invalidate_by_MyISAM_filename_ref \
  &query_cache_invalidate_by_MyISAM_filename
#define query_cache_invalidate_locked_for_write(A, B) \
  query_cache.invalidate_locked_for_write(A, B)
/* note the "maybe": it's a read without mutex */
#define query_cache_maybe_disabled(T)                                 \
  (T->variables.query_cache_type == 0 || query_cache.query_cache_size == 0)
#define query_cache_is_cacheable_query(L) \
  (((L)->sql_command == SQLCOM_SELECT) && (L)->safe_to_cache_query)
#else
#define QUERY_CACHE_FLAGS_SIZE 0
#define query_cache_store_query(A, B)     do { } while(0)
#define query_cache_destroy()             do { } while(0)
#define query_cache_result_size_limit(A)  do { } while(0)
#define query_cache_init()                do { } while(0)
#define query_cache_resize(A)             do { } while(0)
#define query_cache_set_min_res_unit(A)   do { } while(0)
#define query_cache_invalidate3(A, B, C)  do { } while(0)
#define query_cache_invalidate1(A,B)      do { } while(0)
#define query_cache_send_result_to_client(A, B, C) 0
#define query_cache_invalidate_by_MyISAM_filename_ref NULL
#define query_cache_invalidate_locked_for_write(A, B) do { } while(0)

#define query_cache_abort(A,B)            do { } while(0)
#define query_cache_end_of_result(A)      do { } while(0)
#define query_cache_maybe_disabled(T) 1
#define query_cache_is_cacheable_query(L) 0
#endif /*HAVE_QUERY_CACHE*/

extern MYSQL_PLUGIN_IMPORT Query_cache query_cache;
#endif

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