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, 12 deletions

diff --git a/sql/sql_union.cc b/sql/sql_union.cc
index 1b3995f30be..42b67a79683 100644
--- a/sql/sql_union.cc
+++ b/sql/sql_union.cc
@@ -377,21 +377,12 @@ int st_select_lex_unit::exec()
     if (!thd->is_fatal_error)				// Check if EOM
     {
       ulong options_tmp= thd->options;
-      /*
-	We have to take into the account a case when:
-	SET SQL_SELECT_LIMIT was set.
-	In mysql_new_select() function this value was copied to 
-	the fake_select_lex node of the top-level unit.
-	Here below, we just take this value if global LIMIT was not applied
-	to the entire UNION.
-      */
-      ha_rows select_limit= ((global_parameters->select_limit != HA_POS_ERROR) ? 
-			     global_parameters->select_limit : fake_select_lex->select_limit);
       thd->lex->current_select= fake_select_lex;
       offset_limit_cnt= global_parameters->offset_limit;
-      select_limit_cnt= select_limit + 	global_parameters->offset_limit;
+      select_limit_cnt= global_parameters->select_limit +
+	global_parameters->offset_limit;
 
-      if (select_limit_cnt < select_limit)
+      if (select_limit_cnt < global_parameters->select_limit)
 	select_limit_cnt= HA_POS_ERROR;		// no limit
       if (select_limit_cnt == HA_POS_ERROR)
 	options_tmp&= ~OPTION_FOUND_ROWS;