allow to look up queries with leading comments

.bzrignore

@@ -625,3 +625,4 @@ vio/test-ssl
 vio/test-sslclient
 vio/test-sslserver
 vio/viotest-ssl
+libmysqld/sp_cache.cc

mysql-test/r/query_cache.result

@@ -699,3 +699,27 @@ Variable_name	Value
 Qcache_queries_in_cache	2
 SET OPTION SQL_SELECT_LIMIT=DEFAULT;
 drop table t1;
+create table t1 (a int);
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	0
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	41
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	13
+/**/ select * from t1;
+a
+/**/ select * from t1;
+a
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	1
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	42
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	14
+drop table t1;

mysql-test/t/query_cache.test

@@ -477,3 +477,17 @@ select * from t1;
 show status like "Qcache_queries_in_cache";
 SET OPTION SQL_SELECT_LIMIT=DEFAULT;
 drop table t1;
+
+#
+# comments before command
+#
+create table t1 (a int);
+show status like "Qcache_queries_in_cache";
+show status like "Qcache_inserts";
+show status like "Qcache_hits";
+/**/ select * from t1;
+/**/ select * from t1;
+show status like "Qcache_queries_in_cache";
+show status like "Qcache_inserts";
+show status like "Qcache_hits";
+drop table t1;

sql/sql_cache.cc

@@ -905,11 +905,16 @@ Query_cache::send_result_to_client(THD *thd, char *sql, uint query_length)
 
   /*
     Test if the query is a SELECT
-    (pre-space is removed in dispatch_command)
+    (pre-space is removed in dispatch_command).
+
+    First '/' looks like comment before command it is not
+    frequently appeared in real lihe, consequently we can
+    check all such queries, too.
   */
-  if (my_toupper(system_charset_info, sql[0]) != 'S' || 
-      my_toupper(system_charset_info, sql[1]) != 'E' ||
-      my_toupper(system_charset_info,sql[2]) !='L')
+  if ((my_toupper(system_charset_info, sql[0]) != 'S' || 
+       my_toupper(system_charset_info, sql[1]) != 'E' ||
+       my_toupper(system_charset_info,sql[2]) !='L') &&
+      sql[0] != '/')
   {
     DBUG_PRINT("qcache", ("The statement is not a SELECT; Not cached"));
     goto err;