Bug #27792 query cache returns wrong result, with certain system variables

 - Queries in the query cache are identified by the individual 
   characters in the query statement, the current database and 
   the current environment expressed as a set of system variable
   flags.
 - Since the set of environment flags didn't properly describe the
   current environment unexpected results were returned from the 
   query cache.
 - Query cache is now cleared when the variable ft_boolean_syntax is 
   updated.
 - An identification flag for the variable default_week_format is 
   added to the query cache record.
 
Thanks to Martin Friebe who has supplied significant parts of this patch.

mysql-test/r/query_cache.result

@@ -1008,3 +1008,55 @@ Variable_name	Value
 Qcache_hits	1
 drop table t1;
 set GLOBAL query_cache_size=0;
+create table t1 (a int);
+insert into t1 values (1),(2),(3);
+set GLOBAL query_cache_type=1;
+set GLOBAL query_cache_limit=10000;
+set GLOBAL query_cache_min_res_unit=0;
+set GLOBAL query_cache_size= 100000;
+reset query cache;
+set LOCAL default_week_format = 0;
+select week('2007-01-04');
+week('2007-01-04')
+0
+select week('2007-01-04') from t1;
+week('2007-01-04')
+0
+0
+0
+set LOCAL default_week_format = 2;
+select week('2007-01-04');
+week('2007-01-04')
+53
+select week('2007-01-04') from t1;
+week('2007-01-04')
+53
+53
+53
+drop table t1;
+CREATE TABLE t1 (a VARCHAR(200), b TEXT, FULLTEXT (a,b));
+INSERT INTO t1 VALUES('MySQL has now support', 'for full-text search'),
+('Full-text indexes', 'are called collections'),
+('Only MyISAM tables','support collections'),
+('Function MATCH ... AGAINST()','is used to do a search'),
+('Full-text search in MySQL', 'implements vector space model');
+set GLOBAL ft_boolean_syntax='+ -><()~*:""&|';
+select *, MATCH(a,b) AGAINST("+called +collections" IN BOOLEAN MODE) as x from t1;
+a	b	x
+MySQL has now support	for full-text search	0
+Full-text indexes	are called collections	1
+Only MyISAM tables	support collections	0
+Function MATCH ... AGAINST()	is used to do a search	0
+Full-text search in MySQL	implements vector space model	0
+set GLOBAL ft_boolean_syntax='- +><()~*:""&|';
+select *, MATCH(a,b) AGAINST("+called +collections" IN BOOLEAN MODE) as x from t1;
+a	b	x
+MySQL has now support	for full-text search	0
+Full-text indexes	are called collections	0
+Only MyISAM tables	support collections	0
+Function MATCH ... AGAINST()	is used to do a search	0
+Full-text search in MySQL	implements vector space model	0
+set GLOBAL query_cache_type=default;
+set GLOBAL query_cache_limit=default;
+set GLOBAL query_cache_min_res_unit=default;
+set GLOBAL query_cache_size=default;

mysql-test/t/query_cache.test

@@ -729,4 +729,50 @@ drop table t1;
 
 set GLOBAL query_cache_size=0;
 
+#
+# Bug #27792 query cache returns wrong result, with certain system variables
+#
+
+create table t1 (a int);
+insert into t1 values (1),(2),(3);
+set GLOBAL query_cache_type=1;
+set GLOBAL query_cache_limit=10000;
+set GLOBAL query_cache_min_res_unit=0;
+set GLOBAL query_cache_size= 100000;
+
+# default_week_format
+reset query cache;
+set LOCAL default_week_format = 0;
+select week('2007-01-04');
+select week('2007-01-04') from t1;
+
+set LOCAL default_week_format = 2;
+select week('2007-01-04');
+select week('2007-01-04') from t1;
+
+drop table t1;
+
+CREATE TABLE t1 (a VARCHAR(200), b TEXT, FULLTEXT (a,b));
+INSERT INTO t1 VALUES('MySQL has now support', 'for full-text search'),
+                       ('Full-text indexes', 'are called collections'),
+                          ('Only MyISAM tables','support collections'),
+             ('Function MATCH ... AGAINST()','is used to do a search'),
+        ('Full-text search in MySQL', 'implements vector space model');
+
+
+set GLOBAL ft_boolean_syntax='+ -><()~*:""&|';
+
+select *, MATCH(a,b) AGAINST("+called +collections" IN BOOLEAN MODE) as x from t1;
+
+# swap +/-
+set GLOBAL ft_boolean_syntax='- +><()~*:""&|';
+
+select *, MATCH(a,b) AGAINST("+called +collections" IN BOOLEAN MODE) as x from t1;
+
+set GLOBAL query_cache_type=default;
+set GLOBAL query_cache_limit=default;
+set GLOBAL query_cache_min_res_unit=default;
+set GLOBAL query_cache_size=default;
+
+
 # End of 4.1 tests

sql/mysql_priv.h

@@ -426,6 +426,7 @@ struct Query_cache_query_flags
   ulong sql_mode;
   ulong max_sort_length;
   ulong group_concat_max_len;
+  ulong default_week_format;
   MY_LOCALE *lc_time_names;
 };
 #define QUERY_CACHE_FLAGS_SIZE sizeof(Query_cache_query_flags)

sql/set_var.cc

@@ -490,7 +490,7 @@ static sys_var_rand_seed1	sys_rand_seed1("rand_seed1");
 static sys_var_rand_seed2	sys_rand_seed2("rand_seed2");
 
 static sys_var_thd_ulong        sys_default_week_format("default_week_format",
-					                &SV::default_week_format);
+                                                     &SV::default_week_format);
 
 sys_var_thd_ulong               sys_group_concat_max_len("group_concat_max_len",
                                                          &SV::group_concat_max_len);
@@ -992,7 +992,6 @@ bool update_sys_var_str(sys_var_str *var_str, rw_lock_t *var_mutex,
   return 0;
 }
 
-
 static bool sys_update_init_connect(THD *thd, set_var *var)
 {
   return update_sys_var_str(&sys_init_connect, &LOCK_sys_init_connect, var);
@@ -1032,6 +1031,11 @@ static bool sys_update_ftb_syntax(THD *thd, set_var * var)
 {
   strmake(ft_boolean_syntax, var->value->str_value.c_ptr(),
 	  sizeof(ft_boolean_syntax)-1);
+
+#ifdef HAVE_QUERY_CACHE
+  query_cache.flush();
+#endif /* HAVE_QUERY_CACHE */
+
   return 0;
 }
 

sql/sql_cache.cc

@@ -813,6 +813,7 @@ void Query_cache::store_query(THD *thd, TABLE_LIST *tables_used)
     flags.sql_mode= thd->variables.sql_mode;
     flags.max_sort_length= thd->variables.max_sort_length;
     flags.group_concat_max_len= thd->variables.group_concat_max_len;
+    flags.default_week_format= thd->variables.default_week_format;
     flags.lc_time_names= thd->variables.lc_time_names; 
     STRUCT_LOCK(&structure_guard_mutex);
 
@@ -1016,6 +1017,7 @@ Query_cache::send_result_to_client(THD *thd, char *sql, uint query_length)
   flags.sql_mode= thd->variables.sql_mode;
   flags.max_sort_length= thd->variables.max_sort_length;
   flags.group_concat_max_len= thd->variables.group_concat_max_len;
+  flags.default_week_format= thd->variables.default_week_format;
   flags.lc_time_names= thd->variables.lc_time_names; 
   memcpy((void *)(sql + (tot_length - QUERY_CACHE_FLAGS_SIZE)),
 	 &flags, QUERY_CACHE_FLAGS_SIZE);