caching of queries with isammerge tables forbiden using general way

SQL_SELECT_LIMIT as default will be applied only for SELECT statement if there was not explicit LIMIT clause
correct table list passed to class constructor of select_update


mysql-test/r/subselect.result:
  do not show limit if it is not explicit
mysql-test/r/union.result:
  test of LIMIT + ORDER
mysql-test/t/union.test:
  test of LIMIT + ORDER
sql/ha_isammrg.h:
  caching of queries with isammerge tables forbiden
sql/sql_cache.cc:
  removed check on isammerge
sql/sql_lex.cc:
  tag of explicit limit in statement
sql/sql_lex.h:
  tag of explicit limit in statement
sql/sql_parse.cc:
  blanks in empty line removed
  no limit by default (SQL_SELECT_LIMIT as default will be applied only for SELECT statement if there was not explicit LIMIT clause)
sql/sql_union.cc:
  reverted incorrect patch
sql/sql_update.cc:
  reverted incorrect patch
  correct table list passed to class constructor
sql/sql_yacc.yy:
  explicit LIMIT marked

1 files changed, 3 insertions, 4 deletions

diff --git a/sql/sql_cache.cc b/sql/sql_cache.cc
index f17f4bb2b7f..359150cf716 100644
--- a/sql/sql_cache.cc
+++ b/sql/sql_cache.cc
@@ -2612,16 +2612,15 @@ TABLE_COUNTER_TYPE Query_cache::is_cacheable(THD *thd, uint32 query_len,
 	table_alias_charset used here because it depends of
 	lower_case_table_names variable
       */
-      if (tables_used->table->db_type == DB_TYPE_MRG_ISAM ||
-	  tables_used->table->tmp_table != NO_TMP_TABLE ||
+      if (tables_used->table->tmp_table != NO_TMP_TABLE ||
 	  (*tables_type & HA_CACHE_TBL_NOCACHE) ||
 	  (tables_used->db_length == 5 &&
 	   my_strnncoll(table_alias_charset, (uchar*)tables_used->db, 6,
 			(uchar*)"mysql",6) == 0))
       {
 	DBUG_PRINT("qcache", 
-		   ("select not cacheable: used MRG_ISAM, temporary, \
-system or other non-cacheable table(s)"));
+		   ("select not cacheable: temporary, system or \
+other non-cacheable table(s)"));
 	DBUG_RETURN(0);
       }
       if (tables_used->table->db_type == DB_TYPE_MRG_MYISAM)