correct assignment of default limit (BUG#2600)

mysql-test/r/subselect.result:
  test of global limit and subqueries
mysql-test/t/subselect.test:
  test of global limit and subqueries
sql/sql_lex.cc:
  correct detection of non-default limits
sql/sql_parse.cc:
  correct assignment of default limit
sql/sql_yacc.yy:
  correct assignment of default limit

mysql-test/r/subselect.result

@@ -1625,3 +1625,14 @@ PIPPO
 1
 NULL
 DROP TABLE t1, t2;
+create table t1 (a int);
+insert into t1 values (1), (2), (3);
+SET SQL_SELECT_LIMIT=1;
+select sum(a) from (select * from t1) as a;
+sum(a)
+6
+select 2 in (select * from t1);
+2 in (select * from t1)
+1
+SET SQL_SELECT_LIMIT=default;
+drop table t1;

mysql-test/t/subselect.test

@@ -1075,3 +1075,14 @@ s.id_cns = cns.id ORDER BY s.anno_dep DESC LIMIT 1) AS PIPPO FROM
 t2 AS cns;
 
 DROP TABLE t1, t2;
+
+#
+# GLOBAL LIMIT
+#
+create table t1 (a int);
+insert into t1 values (1), (2), (3);
+SET SQL_SELECT_LIMIT=1;
+select sum(a) from (select * from t1) as a;
+select 2 in (select * from t1);
+SET SQL_SELECT_LIMIT=default;
+drop table t1;

sql/sql_lex.cc

@@ -1540,8 +1540,9 @@ void st_select_lex::print_limit(THD *thd, String *str)
   if (!thd)
     thd= current_thd;
 
-  if (select_limit != thd->variables.select_limit ||
-      select_limit != HA_POS_ERROR ||
+  if ((select_limit != thd->variables.select_limit &&
+       this == &thd->lex->select_lex) ||
+      (select_limit != HA_POS_ERROR && this != &thd->lex->select_lex) ||
       offset_limit != 0L)
   {
     str->append(" limit ", 7);

sql/sql_parse.cc

@@ -3758,7 +3758,9 @@ mysql_init_select(LEX *lex)
 {
   SELECT_LEX *select_lex= lex->current_select;
   select_lex->init_select();
-  select_lex->select_limit= lex->thd->variables.select_limit;
+  select_lex->select_limit= (&lex->select_lex == select_lex) ?
+	lex->thd->variables.select_limit :	/* Primry UNION */
+	HA_POS_ERROR;				/* subquery */
   if (select_lex == &lex->select_lex)
   {
     lex->exchange= 0;
@@ -3810,7 +3812,9 @@ mysql_new_select(LEX *lex, bool move_down)
       fake->select_number= INT_MAX;
       fake->make_empty_select();
       fake->linkage= GLOBAL_OPTIONS_TYPE;
-      fake->select_limit= lex->thd->variables.select_limit;
+      fake->select_limit= (&lex->unit == unit) ?
+	lex->thd->variables.select_limit :	/* Primry UNION */
+	HA_POS_ERROR;				/* subquery */
     }
   }
 

sql/sql_yacc.yy

@@ -3476,9 +3476,12 @@ order_dir:
 opt_limit_clause_init:
 	/* empty */
 	{
-	  SELECT_LEX *sel= Select;
+	  LEX *lex= Lex;
+	  SELECT_LEX *sel= lex->current_select;
           sel->offset_limit= 0L;
-          sel->select_limit= Lex->thd->variables.select_limit;
+          sel->select_limit= (&lex->select_lex == sel) ?
+	    Lex->thd->variables.select_limit :	/* primary SELECT */
+	    HA_POS_ERROR;			/* subquery */
 	}
 	| limit_clause {}
 	;