invalidation of locking for write tables (BUG#2693)

fixed linking query_prealloc_size to query cache presence

mysql-test/r/query_cache.result

@@ -687,4 +687,21 @@ select * from t3;
 delete from t4 where a=1;
 flush query cache;
 drop table t1,t2,t3,t4;
+set query_cache_wlock_invalidate=1;
+create table t1 (a int not null);
+create table t2 (a int not null);
+select * from t1;
+a
+select * from t2;
+a
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	2
+lock table t1 write, t2 read;
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	1
+unlock table;
+drop table t1,t2;
+set query_cache_wlock_invalidate=default;
 set GLOBAL query_cache_size=0;

mysql-test/t/query_cache.test

@@ -504,6 +504,21 @@ select * from t3;
 enable_result_log;
 delete from t4 where a=1;
 flush query cache;
-
 drop table t1,t2,t3,t4;
+
+#
+# WRITE LOCK & QC
+#
+set query_cache_wlock_invalidate=1;
+create table t1 (a int not null);
+create table t2 (a int not null);
+select * from t1;
+select * from t2;
+show status like "Qcache_queries_in_cache";
+lock table t1 write, t2 read;
+show status like "Qcache_queries_in_cache";
+unlock table;
+drop table t1,t2;
+set query_cache_wlock_invalidate=default;
+
 set GLOBAL query_cache_size=0;

sql/mysqld.cc

@@ -3228,7 +3228,7 @@ enum options_mysqld {
   OPT_NET_READ_TIMEOUT, OPT_NET_WRITE_TIMEOUT,
   OPT_OPEN_FILES_LIMIT, 
   OPT_QUERY_CACHE_LIMIT, OPT_QUERY_CACHE_SIZE,
-  OPT_QUERY_CACHE_TYPE, OPT_RECORD_BUFFER,
+  OPT_QUERY_CACHE_TYPE, OPT_QUERY_CACHE_WLOCK_INVALIDATE, OPT_RECORD_BUFFER,
   OPT_RECORD_RND_BUFFER, OPT_RELAY_LOG_SPACE_LIMIT,
   OPT_SLAVE_NET_TIMEOUT, OPT_SLAVE_COMPRESSED_PROTOCOL, OPT_SLOW_LAUNCH_TIME,
   OPT_READONLY, OPT_DEBUGGING,
@@ -4015,12 +4015,17 @@ this value; if zero (the default): when the size exceeds max_binlog_size. \
    (gptr*) &global_system_variables.query_cache_type,
    (gptr*) &max_system_variables.query_cache_type,
    0, GET_ULONG, REQUIRED_ARG, 1, 0, 2, 0, 1, 0},
+  {"query_cache_wlock_invalidate", OPT_QUERY_CACHE_WLOCK_INVALIDATE,
+   "Invalidate queries in query cache on LOCK for write",
+   (gptr*) &global_system_variables.query_cache_wlock_invalidate,
+   (gptr*) &max_system_variables.query_cache_wlock_invalidate,
+   0, GET_BOOL, NO_ARG, 0, 0, 1, 0, 1, 0},
+#endif /*HAVE_QUERY_CACHE*/
   {"query_prealloc_size", OPT_QUERY_PREALLOC_SIZE,
    "Persistent buffer for query parsing and execution",
    (gptr*) &global_system_variables.query_prealloc_size,
    (gptr*) &max_system_variables.query_prealloc_size, 0, GET_ULONG,
    REQUIRED_ARG, QUERY_ALLOC_PREALLOC_SIZE, 1024, ~0L, 0, 1024, 0},
-#endif /*HAVE_QUERY_CACHE*/
   {"read_buffer_size", OPT_RECORD_BUFFER,
    "Each thread that does a sequential scan allocates a buffer of this size for each table it scans. If you do many sequential scans, you may want to increase this value.",
    (gptr*) &global_system_variables.read_buff_size,

sql/set_var.cc

@@ -229,6 +229,9 @@ sys_var_long_ptr	sys_query_cache_limit("query_cache_limit",
 sys_var_thd_enum	sys_query_cache_type("query_cache_type",
 					     &SV::query_cache_type,
 					     &query_cache_type_typelib);
+sys_var_thd_bool
+sys_query_cache_wlock_invalidate("query_cache_wlock_invalidate",
+				 &SV::query_cache_wlock_invalidate);
 #endif /* HAVE_QUERY_CACHE */
 sys_var_long_ptr	sys_server_id("server_id",&server_id);
 sys_var_bool_ptr	sys_slave_compressed_protocol("slave_compressed_protocol",
@@ -405,6 +408,7 @@ sys_var *sys_variables[]=
 #ifdef HAVE_QUERY_CACHE
   &sys_query_cache_limit,
   &sys_query_cache_type,
+  &sys_query_cache_wlock_invalidate,
 #endif /* HAVE_QUERY_CACHE */
   &sys_quote_show_create,
   &sys_rand_seed1,

sql/sql_cache.cc

@@ -1090,6 +1090,37 @@ void Query_cache::invalidate(CHANGED_TABLE_LIST *tables_used)
   DBUG_VOID_RETURN;
 }
 
+
+/*
+  Invalidate locked for write
+
+  SYNOPSIS
+    Query_cache::invalidate_locked_for_write()
+    tables_used - table list
+
+  NOTE
+    can be used only for opened tables
+*/
+void Query_cache::invalidate_locked_for_write(TABLE_LIST *tables_used)
+{
+  DBUG_ENTER("Query_cache::invalidate (changed table list)");
+  if (query_cache_size > 0 && tables_used)
+  {
+    STRUCT_LOCK(&structure_guard_mutex);
+    if (query_cache_size > 0)
+    {
+      DUMP(this);
+      for (; tables_used; tables_used= tables_used->next)
+      {
+	if (tables_used->lock_type & (TL_WRITE_LOW_PRIORITY | TL_WRITE))
+	  invalidate_table(tables_used->table);
+      }
+    }
+    STRUCT_UNLOCK(&structure_guard_mutex);
+  }
+  DBUG_VOID_RETURN;
+}
+
 /*
   Remove all cached queries that uses the given table
 */

sql/sql_cache.h

@@ -360,6 +360,7 @@ class Query_cache
   void invalidate(THD* thd, TABLE_LIST *tables_used,
 		  my_bool using_transactions);
   void invalidate(CHANGED_TABLE_LIST *tables_used);
+  void invalidate_locked_for_write(TABLE_LIST *tables_used);
   void invalidate(THD* thd, TABLE *table, my_bool using_transactions);
   void invalidate(THD *thd, const char *key, uint32  key_length,
 		  my_bool using_transactions);

sql/sql_class.h

@@ -336,6 +336,7 @@ struct system_variables
   my_bool log_warnings;
   my_bool low_priority_updates;
   my_bool new_mode;
+  my_bool query_cache_wlock_invalidate;
 
   CONVERT *convert_set;
 };

sql/sql_parse.cc

@@ -2307,8 +2307,12 @@ mysql_execute_command(void)
       goto error;
     thd->in_lock_tables=1;
     thd->options|= OPTION_TABLE_LOCK;
-    if (!(res=open_and_lock_tables(thd,tables)))
+    if (!(res= open_and_lock_tables(thd, tables)))
     {
+#ifdef HAVE_QUERY_CACHE
+      if (thd->variables.query_cache_wlock_invalidate)
+	query_cache.invalidate_locked_for_write(tables);
+#endif /*HAVE_QUERY_CACHE*/
       thd->locked_tables=thd->lock;
       thd->lock=0;
       send_ok(&thd->net);