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

@@ -266,7 +266,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	3	Using where
 2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	3	
 Warnings:
-Note	1003	select high_priority test.t3.a AS `a` from test.t3 where (test.t3.a >= (select min(test.t2.b) from test.t2 limit 1))
+Note	1003	select high_priority test.t3.a AS `a` from test.t3 where (test.t3.a >= (select min(test.t2.b) from test.t2))
 select * from t3 where a >= all (select b from t2);
 a
 7
@@ -327,7 +327,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	DEPENDENT SUBQUERY	t7	eq_ref	PRIMARY	PRIMARY	4	test.t6.clinic_uq	1	
 Warnings:
 Note	1276	Field or reference 'clinic_uq' of SELECT #2 was resolved in SELECT #1
-Note	1003	select high_priority test.t6.patient_uq AS `patient_uq`,test.t6.clinic_uq AS `clinic_uq` from test.t6 where exists(select test.t7.uq AS `uq`,test.t7.name AS `name` from test.t7 where (test.t7.uq = test.t6.clinic_uq) limit 1)
+Note	1003	select high_priority test.t6.patient_uq AS `patient_uq`,test.t6.clinic_uq AS `clinic_uq` from test.t6 where exists(select test.t7.uq AS `uq`,test.t7.name AS `name` from test.t7 where (test.t7.uq = test.t6.clinic_uq))
 select * from t1 where a= (select a from t2,t4 where t2.b=t4.b);
 ERROR 23000: Column: 'a' in field list is ambiguous
 drop table if exists t1,t2,t3;
@@ -728,7 +728,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
-Note	1003	select high_priority test.t2.id AS `id` from test.t2 where <in_optimizer>(test.t2.id,<exists>(select 1 AS `Not_used` having (<cache>(test.t2.id) = <null_helper>(1)) limit 1 union select 1 AS `Not_used` having (<cache>(test.t2.id) = <null_helper>(3)) limit 1))
+Note	1003	select high_priority test.t2.id AS `id` from test.t2 where <in_optimizer>(test.t2.id,<exists>(select 1 AS `Not_used` having (<cache>(test.t2.id) = <null_helper>(1)) union select 1 AS `Not_used` having (<cache>(test.t2.id) = <null_helper>(3))))
 SELECT * FROM t2 WHERE id IN (SELECT 5 UNION SELECT 3);
 id
 SELECT * FROM t2 WHERE id IN (SELECT 5 UNION SELECT 2);
@@ -891,7 +891,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	DEPENDENT SUBQUERY	t2	ref_or_null	a	a	5	func	2	Using where; Using index
 2	DEPENDENT SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	3	Using where
 Warnings:
-Note	1003	select high_priority test.t1.a AS `a`,<in_optimizer>(test.t1.a,<exists>(select 1 AS `Not_used` from test.t2 join test.t3 where ((test.t3.a = test.t2.a) and ((<cache>(test.t1.a) = test.t2.a) or isnull(test.t2.a))) having <is_not_null_test>(test.t2.a) limit 1)) AS `t1.a in (select t2.a from t2,t3 where t3.a=t2.a)` from test.t1
+Note	1003	select high_priority test.t1.a AS `a`,<in_optimizer>(test.t1.a,<exists>(select 1 AS `Not_used` from test.t2 join test.t3 where ((test.t3.a = test.t2.a) and ((<cache>(test.t1.a) = test.t2.a) or isnull(test.t2.a))) having <is_not_null_test>(test.t2.a))) AS `t1.a in (select t2.a from t2,t3 where t3.a=t2.a)` from test.t1
 drop table t1,t2,t3;
 create table t1 (a float);
 select 10.5 IN (SELECT * from t1 LIMIT 1);
@@ -1162,7 +1162,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 Warnings:
-Note	1003	select high_priority <in_optimizer>(0,<exists>(select 1 AS `Not_used` from test.t1 a limit 1)) AS `0 IN (SELECT 1 FROM t1 a)`
+Note	1003	select high_priority <in_optimizer>(0,<exists>(select 1 AS `Not_used` from test.t1 a)) AS `0 IN (SELECT 1 FROM t1 a)`
 INSERT INTO t1 (pseudo) VALUES ('test1');
 SELECT 0 IN (SELECT 1 FROM t1 a);
 0 IN (SELECT 1 FROM t1 a)
@@ -1172,7 +1172,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 Warnings:
-Note	1003	select high_priority <in_optimizer>(0,<exists>(select 1 AS `Not_used` from test.t1 a limit 1)) AS `0 IN (SELECT 1 FROM t1 a)`
+Note	1003	select high_priority <in_optimizer>(0,<exists>(select 1 AS `Not_used` from test.t1 a)) AS `0 IN (SELECT 1 FROM t1 a)`
 drop table t1;
 CREATE TABLE `t1` (
 `i` int(11) NOT NULL default '0',
@@ -1304,7 +1304,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	DEPENDENT SUBQUERY	t1	eq_ref	PRIMARY	PRIMARY	4	func	1	Using where
 2	DEPENDENT SUBQUERY	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.b	1	Using where; Using index
 Warnings:
-Note	1003	select high_priority test.t2.a AS `a` from test.t2 where <in_optimizer>(test.t2.a,<exists>(select 1 AS `Not_used` from test.t1 join test.t3 where ((test.t1.b = test.t3.a) and (<cache>(test.t2.a) = test.t1.a)) limit 1))
+Note	1003	select high_priority test.t2.a AS `a` from test.t2 where <in_optimizer>(test.t2.a,<exists>(select 1 AS `Not_used` from test.t1 join test.t3 where ((test.t1.b = test.t3.a) and (<cache>(test.t2.a) = test.t1.a))))
 drop table t1, t2, t3;
 create table t1 (a int, b int, index a (a,b));
 create table t2 (a int, index a (a));
@@ -1343,7 +1343,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	DEPENDENT SUBQUERY	t1	ref	a	a	5	func	1001	Using where; Using index
 2	DEPENDENT SUBQUERY	t3	index	a	a	5	NULL	3	Using where; Using index
 Warnings:
-Note	1003	select high_priority test.t2.a AS `a` from test.t2 where <in_optimizer>(test.t2.a,<exists>(select 1 AS `Not_used` from test.t1 join test.t3 where ((test.t1.b = test.t3.a) and (<cache>(test.t2.a) = test.t1.a)) limit 1))
+Note	1003	select high_priority test.t2.a AS `a` from test.t2 where <in_optimizer>(test.t2.a,<exists>(select 1 AS `Not_used` from test.t1 join test.t3 where ((test.t1.b = test.t3.a) and (<cache>(test.t2.a) = test.t1.a))))
 insert into t1 values (3,31);
 select * from t2 where t2.a in (select a from t1 where t1.b <> 30);
 a
@@ -1483,7 +1483,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	3	Using where
 2	SUBQUERY	t2	system	NULL	NULL	NULL	NULL	0	const row not found
 Warnings:
-Note	1003	select high_priority test.t3.a AS `a` from test.t3 where <not>((test.t3.a < (select max(test.t2.b) from test.t2 limit 1)))
+Note	1003	select high_priority test.t3.a AS `a` from test.t3 where <not>((test.t3.a < (select max(test.t2.b) from test.t2)))
 insert into t2 values (2,2), (2,1), (3,3), (3,1);
 select * from t3 where a > all (select max(b) from t2 group by a);
 a
@@ -1666,7 +1666,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	DEPENDENT SUBQUERY	t1	eq_ref	PRIMARY	PRIMARY	4	test.tt.id	7	Using where; Using index
 Warnings:
 Note	1276	Field or reference 'tt.id' of SELECT #2 was resolved in SELECT #1
-Note	1003	select high_priority test.tt.id AS `id`,test.tt.text AS `text` from test.t1 tt where not(exists(select test.t1.id AS `id` from test.t1 where ((test.t1.id < 8) and ((test.t1.id = test.tt.id) or isnull(test.t1.id))) having (test.t1.id is not null) limit 1))
+Note	1003	select high_priority test.tt.id AS `id`,test.tt.text AS `text` from test.t1 tt where not(exists(select test.t1.id AS `id` from test.t1 where ((test.t1.id < 8) and ((test.t1.id = test.tt.id) or isnull(test.t1.id))) having (test.t1.id is not null)))
 insert into t1 (id, text) values (1000, 'text1000'), (1001, 'text1001');
 create table t2 (id int not null, text varchar(20) not null default '', primary key (id));
 insert into t2 (id, text) values (1, 'text1'), (2, 'text2'), (3, 'text3'), (4, 'text4'), (5, 'text5'), (6, 'text6'), (7, 'text7'), (8, 'text8'), (9, 'text9'), (10, 'text10'), (11, 'text1'), (12, 'text2'), (13, 'text3'), (14, 'text4'), (15, 'text5'), (16, 'text6'), (17, 'text7'), (18, 'text8'), (19, 'text9'), (20, 'text10'),(21, 'text1'), (22, 'text2'), (23, 'text3'), (24, 'text4'), (25, 'text5'), (26, 'text6'), (27, 'text7'), (28, 'text8'), (29, 'text9'), (30, 'text10'), (31, 'text1'), (32, 'text2'), (33, 'text3'), (34, 'text4'), (35, 'text5'), (36, 'text6'), (37, 'text7'), (38, 'text8'), (39, 'text9'), (40, 'text10'), (41, 'text1'), (42, 'text2'), (43, 'text3'), (44, 'text4'), (45, 'text5'), (46, 'text6'), (47, 'text7'), (48, 'text8'), (49, 'text9'), (50, 'text10');

mysql-test/r/union.result

@@ -936,3 +936,17 @@ select 1 union select 2;
 1
 2
 set sql_select_limit=default;
+create table t1 (a int);
+insert into t1 values (100), (1);
+create table t2 (a int);
+insert into t2 values (100);
+select a from t1 union select a from t2 order by a;
+a
+1
+100
+SET SQL_SELECT_LIMIT=1;
+select a from t1 union select a from t2 order by a;
+a
+1
+drop table t1, t2;
+set sql_select_limit=default;

mysql-test/t/union.test

@@ -504,3 +504,15 @@ select 1 union select 2;
 (select 1) union (select 2) union (select 3) limit 2;
 set sql_select_limit=default;
 
+#
+# ORDER with LIMIT
+#
+create table t1 (a int);
+insert into t1 values (100), (1);
+create table t2 (a int);
+insert into t2 values (100);
+select a from t1 union select a from t2 order by a;
+SET SQL_SELECT_LIMIT=1;
+select a from t1 union select a from t2 order by a;
+drop table t1, t2;
+set sql_select_limit=default;

sql/ha_isammrg.h

@@ -68,4 +68,5 @@ class ha_isammrg: public handler
   int create(const char *name, TABLE *form, HA_CREATE_INFO *create_info);
   THR_LOCK_DATA **store_lock(THD *thd, THR_LOCK_DATA **to,
 			     enum thr_lock_type lock_type);
+  uint8 table_cache_type() { return HA_CACHE_TBL_NOCACHE; }
 };

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)

sql/sql_lex.cc

@@ -1023,6 +1023,7 @@ void st_select_lex::init_query()
   ref_pointer_array= 0;
   select_n_having_items= 0;
   prep_where= 0;
+  explicit_limit= 0;
 }
 
 void st_select_lex::init_select()
@@ -1616,10 +1617,7 @@ void st_select_lex::print_limit(THD *thd, String *str)
   if (!thd)
     thd= current_thd;
 
-  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)
+  if (explicit_limit)
   {
     str->append(" limit ", 7);
     char buff[20];

sql/sql_lex.h

@@ -418,6 +418,8 @@ class st_select_lex: public st_select_lex_node
   bool  braces;   	/* SELECT ... UNION (SELECT ... ) <- this braces */
   /* TRUE when having fix field called in processing of this SELECT */
   bool having_fix_field;
+  /* explicit LIMIT clause was used */
+  bool explicit_limit;
 
   /* 
      SELECT for SELECT command st_select_lex. Used to privent scaning

sql/sql_parse.cc

@@ -1874,7 +1874,7 @@ mysql_execute_command(THD *thd)
   if (&lex->select_lex != lex->all_selects_list &&
       lex->unit.create_total_list(thd, lex, &tables))
     DBUG_VOID_RETURN;
-  
+
   /*
     When option readonly is set deny operations which change tables.
     Except for the replication thread and the 'super' users.
@@ -1891,6 +1891,13 @@ mysql_execute_command(THD *thd)
   switch (lex->sql_command) {
   case SQLCOM_SELECT:
   {
+    /* assign global limit variable if limit is not given */
+    {
+      SELECT_LEX *param= lex->unit.global_parameters;
+      if (!param->explicit_limit)
+	param->select_limit= thd->variables.select_limit;
+    }
+
     select_result *result=lex->result;
     if (tables)
     {
@@ -3742,9 +3749,7 @@ mysql_init_select(LEX *lex)
 {
   SELECT_LEX *select_lex= lex->current_select;
   select_lex->init_select();
-  select_lex->select_limit= (&lex->select_lex == select_lex) ?
-	lex->thd->variables.select_limit :	/* Primry UNION */
-	HA_POS_ERROR;				/* subquery */
+  select_lex->select_limit= HA_POS_ERROR;
   if (select_lex == &lex->select_lex)
   {
     lex->exchange= 0;
@@ -3796,9 +3801,7 @@ 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->unit == unit) ?
-	lex->thd->variables.select_limit :	/* Primry UNION */
-	HA_POS_ERROR;				/* subquery */
+      fake->select_limit= HA_POS_ERROR;
     }
   }
 

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;

sql/sql_update.cc

@@ -544,7 +544,7 @@ int mysql_multi_update(THD *thd,
     }
   }
 
-  if (!(result=new multi_update(thd, table_list, fields, values,
+  if (!(result=new multi_update(thd, update_list, fields, values,
 				handle_duplicates)))
     DBUG_RETURN(-1);
 
@@ -578,7 +578,7 @@ multi_update::multi_update(THD *thd_arg, TABLE_LIST *table_list,
 int multi_update::prepare(List<Item> &not_used_values,
 			  SELECT_LEX_UNIT *lex_unit)
 {
-  TABLE_LIST *table_ref, *tables;
+  TABLE_LIST *table_ref;
   SQL_LIST update;
   table_map tables_to_update= 0;
   Item_field *item;
@@ -604,9 +604,8 @@ int multi_update::prepare(List<Item> &not_used_values,
     We have to check values after setup_tables to get used_keys right in
     reference tables
   */
-  tables= thd->lex->select_lex.get_table_list();
 
-  if (setup_fields(thd, 0, tables, *values, 1, 0, 0))
+  if (setup_fields(thd, 0, all_tables, *values, 1, 0, 0))
     DBUG_RETURN(1);
 
   /*
@@ -616,7 +615,7 @@ int multi_update::prepare(List<Item> &not_used_values,
   */
 
   update.empty();
-  for (table_ref= tables;  table_ref; table_ref=table_ref->next)
+  for (table_ref= all_tables;  table_ref; table_ref=table_ref->next)
   {
     TABLE *table=table_ref->table;
     if (tables_to_update & table->map)
@@ -685,10 +684,10 @@ int multi_update::prepare(List<Item> &not_used_values,
     which will cause an error when reading a row.
     (This issue is mostly relevent for MyISAM tables)
   */
-  for (table_ref= tables;  table_ref; table_ref=table_ref->next)
+  for (table_ref= all_tables;  table_ref; table_ref=table_ref->next)
   {
     TABLE *table=table_ref->table;
-    if (!(tables_to_update & table->map) || !table->no_keyread && 
+    if (!(tables_to_update & table->map) && 
 	find_real_table_in_list(update_tables, table_ref->db,
 				table_ref->real_name))
       table->no_cache= 1;			// Disable row cache

sql/sql_yacc.yy

@@ -3566,9 +3566,7 @@ opt_limit_clause_init:
 	  LEX *lex= Lex;
 	  SELECT_LEX *sel= lex->current_select;
           sel->offset_limit= 0L;
-          sel->select_limit= (&lex->select_lex == sel) ?
-	    Lex->thd->variables.select_limit :	/* primary SELECT */
-	    HA_POS_ERROR;			/* subquery */
+          sel->select_limit= HA_POS_ERROR;
 	}
 	| limit_clause {}
 	;
@@ -3588,18 +3586,21 @@ limit_options:
             SELECT_LEX *sel= Select;
             sel->select_limit= $1;
             sel->offset_limit= 0L;
+	    sel->explicit_limit= 1;
 	  }
 	| ULONG_NUM ',' ULONG_NUM
 	  {
 	    SELECT_LEX *sel= Select;
 	    sel->select_limit= $3;
 	    sel->offset_limit= $1;
+	    sel->explicit_limit= 1;
 	  }
 	| ULONG_NUM OFFSET_SYM ULONG_NUM
 	  {
 	    SELECT_LEX *sel= Select;
 	    sel->select_limit= $1;
 	    sel->offset_limit= $3;
+	    sel->explicit_limit= 1;
 	  }
 	;
 
@@ -3611,7 +3612,11 @@ delete_limit_clause:
 	  lex->current_select->select_limit= HA_POS_ERROR;
 	}
 	| LIMIT ulonglong_num
-	{ Select->select_limit= (ha_rows) $2; };
+	{
+	  SELECT_LEX *sel= Select;
+	  sel->select_limit= (ha_rows) $2;
+	  sel->explicit_limit= 1;
+	};
 
 ULONG_NUM:
 	NUM	    { $$= strtoul($1.str,NULL,10); }