Introduce thd->query_cache_tls (thread

local storage for query cache). 
We need more than one pointer in a thread to
represent the query cache and net->query_cache_query can not be used
any more (due to ABI compatibility issues and to different life
time of NET and THD).
This is a backport of the following patch from 6.0:
----------------------------------------------------------
revno: 2476.1157.2
committer: kostja@bodhi.(none)
timestamp: Sat 2007-06-16 13:29:24 +0400

include/mysql.h.pp

@@ -32,7 +32,7 @@ typedef struct st_net {
   my_bool unused2;
   my_bool compress;
   my_bool unused3;
-  unsigned char *query_cache_query;
+  unsigned char *unused;
   unsigned int last_errno;
   unsigned char error;
   my_bool unused4;

include/mysql_com.h

@@ -264,10 +264,9 @@ typedef struct st_net {
   */
 #endif
   /*
-    'query_cache_query' should be accessed only via query cache
-    functions and methods to maintain proper locking.
+    Unused, please remove with the next incompatible ABI change.
   */
-  unsigned char *query_cache_query;
+  unsigned char *unused;
   unsigned int last_errno;
   unsigned char error; 
   my_bool unused4; /* Please remove with the next incompatible ABI change. */

sql/mysql_priv.h

@@ -905,6 +905,8 @@ struct Query_cache_query_flags
 };
 #define QUERY_CACHE_FLAGS_SIZE sizeof(Query_cache_query_flags)
 #include "sql_cache.h"
+#define query_cache_abort(A) query_cache.abort(A)
+#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)

sql/net_serv.cc

@@ -95,8 +95,8 @@ extern pthread_mutex_t LOCK_bytes_sent , LOCK_bytes_received;
 #ifndef MYSQL_INSTANCE_MANAGER
 #ifdef HAVE_QUERY_CACHE
 #define USE_QUERY_CACHE
-extern void query_cache_init_query(NET *net);
-extern void query_cache_insert(NET *net, const char *packet, ulong length);
+extern void query_cache_insert(const char *packet, ulong length,
+                               unsigned pkt_nr);
 #endif // HAVE_QUERY_CACHE
 #define update_statistics(A) A
 #endif /* MYSQL_INSTANCE_MANGER */
@@ -132,11 +132,7 @@ my_bool my_net_init(NET *net, Vio* vio)
   net->compress=0; net->reading_or_writing=0;
   net->where_b = net->remain_in_buf=0;
   net->last_errno=0;
-#ifdef USE_QUERY_CACHE
-  query_cache_init_query(net);
-#else
-  net->query_cache_query= 0;
-#endif
+  net->unused= 0;
 
   if (vio != 0)					/* If real connection */
   {
@@ -586,7 +582,7 @@ net_real_write(NET *net,const uchar *packet, size_t len)
   DBUG_ENTER("net_real_write");
 
 #if defined(MYSQL_SERVER) && defined(USE_QUERY_CACHE)
-  query_cache_insert(net, (char*) packet, len);
+  query_cache_insert((char*) packet, len, net->pkt_nr);
 #endif
 
   if (net->error == 2)

sql/sql_cache.h

@@ -64,6 +64,8 @@ struct Query_cache_table;
 struct Query_cache_query;
 struct Query_cache_result;
 class Query_cache;
+struct Query_cache_tls;
+struct st_lex;
 
 /**
   This class represents a node in the linked chain of queries
@@ -137,7 +139,7 @@ struct Query_cache_query
   ulonglong limit_found_rows;
   rw_lock_t lock;
   Query_cache_block *res;
-  NET *wri;
+  Query_cache_tls *wri;
   ulong len;
   uint8 tbls_type;
   unsigned int last_pkt_nr;
@@ -149,8 +151,8 @@ struct Query_cache_query
   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 NET *writer()			   { return wri; }
-  inline void writer(NET *p)		   { wri= 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 ulong length()			   { return len; }
@@ -407,7 +409,8 @@ protected:
     If query is cacheable return number tables in query
     (query without tables not cached)
   */
-  TABLE_COUNTER_TYPE is_cacheable(THD *thd, uint32 query_len, char *query,
+  TABLE_COUNTER_TYPE is_cacheable(THD *thd, size_t query_len,
+                                  const char *query,
                                   LEX *lex, TABLE_LIST *tables_used,
                                   uint8 *tables_type);
   TABLE_COUNTER_TYPE process_and_count_tables(THD *thd,
@@ -462,10 +465,13 @@ protected:
 
   void destroy();
 
-  friend void query_cache_init_query(NET *net);
-  friend void query_cache_insert(NET *net, const char *packet, ulong length);
-  friend void query_cache_end_of_result(THD *thd);
-  friend void query_cache_abort(NET *net);
+  void insert(Query_cache_tls *query_cache_tls,
+              const char *packet,
+              ulong length,
+              unsigned pkt_nr);
+
+  void end_of_result(THD *thd);
+  void abort(Query_cache_tls *query_cache_tls);
 
   /*
     The following functions are only used when debugging
@@ -493,9 +499,4 @@ protected:
 
 extern Query_cache query_cache;
 extern TYPELIB query_cache_type_typelib;
-void query_cache_init_query(NET *net);
-void query_cache_insert(NET *net, const char *packet, ulong length);
-void query_cache_end_of_result(THD *thd);
-void query_cache_abort(NET *net);
-
 #endif

sql/sql_class.cc

@@ -501,9 +501,6 @@ THD::THD()
   net.vio=0;
 #endif
   client_capabilities= 0;                       // minimalistic client
-#ifdef HAVE_QUERY_CACHE
-  query_cache_init_query(&net);                 // If error on boot
-#endif
   ull=0;
   system_thread= NON_SYSTEM_THREAD;
   cleanup_done= abort_on_warning= no_warnings_for_error= 0;
@@ -796,7 +793,7 @@ THD::raise_condition_no_handler(uint sql_errno,
   MYSQL_ERROR *cond= NULL;
   DBUG_ENTER("THD::raise_condition_no_handler");
 
-  query_cache_abort(& net);
+  query_cache_abort(&query_cache_tls);
 
   /* FIXME: broken special case */
   if (no_warnings_for_error && (level == MYSQL_ERROR::WARN_LEVEL_ERROR))

sql/sql_class.h

@@ -315,6 +315,27 @@ typedef enum enum_diag_condition_item_name
 */
 extern const LEX_STRING Diag_condition_item_names[];
 
+/**
+  Query_cache_tls -- query cache thread local data.
+*/
+
+class Query_cache_block;
+
+struct Query_cache_tls
+{
+  /*
+    'first_query_block' should be accessed only via query cache
+    functions and methods to maintain proper locking.
+  */
+  Query_cache_block *first_query_block;
+  void set_first_query_block(Query_cache_block *first_query_block_arg)
+  {
+    first_query_block= first_query_block_arg;
+  }
+
+  Query_cache_tls() :first_query_block(NULL) {}
+};
+
 #include "sql_lex.h"				/* Must be here */
 
 class Delayed_insert;
@@ -1239,6 +1260,9 @@ public:
     fields then.
   */
   struct st_mysql_stmt *current_stmt;
+#endif
+#ifdef HAVE_QUERY_CACHE
+  Query_cache_tls query_cache_tls;
 #endif
   NET	  net;				// client connection descriptor
   Protocol *protocol;			// Current protocol

sql/sql_parse.cc

@@ -6026,7 +6026,7 @@ void mysql_parse(THD *thd, const char *inBuf, uint length,
       DBUG_PRINT("info",("Command aborted. Fatal_error: %d",
 			 thd->is_fatal_error));
 
-      query_cache_abort(&thd->net);
+      query_cache_abort(&thd->query_cache_tls);
     }
     if (thd->lex->sphead)
     {

sql/sql_select.cc

@@ -9187,7 +9187,7 @@ remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value)
            thd->substitute_null_with_insert_id))
       {
 #ifdef HAVE_QUERY_CACHE
-	query_cache_abort(&thd->net);
+	query_cache_abort(&thd->query_cache_tls);
 #endif
 	COND *new_cond;
 	if ((new_cond= new Item_func_eq(args[0],