Merge

mysql-test/r/derived_view.result

@@ -1889,5 +1889,22 @@ ORDER BY CONCAT(alias2.col_varchar_nokey);
 col_varchar_key	pk	col_varchar_key	col_varchar_nokey
 set max_heap_table_size= @tmp_882994;
 drop table t1,t2,t3;
+#
+# LP bug #917990: Bad estimate of #rows for derived table with LIMIT
+#
+CREATE TABLE t1 (a int);
+INSERT INTO t1 VALUES
+(8), (3), (4), (7), (9), (5), (1), (2);
+SELECT * FROM (SELECT * FROM t1 LIMIT 3) t;
+a
+8
+3
+4
+EXPLAIN
+SELECT * FROM (SELECT * FROM t1 LIMIT 3) t;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	3	
+2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	8	
+DROP TABLE t1;
 set optimizer_switch=@exit_optimizer_switch;
 set join_cache_level=@exit_join_cache_level;

mysql-test/r/view.result

@@ -304,7 +304,7 @@ a+1
 4
 explain select * from v1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	4	
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
 2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	4	Using filesort
 drop view v1;
 drop table t1;

mysql-test/suite/vcol/r/vcol_view_innodb.result

@@ -107,7 +107,7 @@ MariaDB-5.3: the following EXPLAIN produces incorrect #rows for table t1.
 MariaDB-5.3: this is expected to go away when FROM subquery optimizations are pushed
 explain select * from v1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	4	
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
 2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	4	Using filesort
 drop view v1;
 create view v1 as select c+1 from t1 order by 1 desc limit 2;
@@ -119,7 +119,7 @@ MariaDB-5.3: the following EXPLAIN produces incorrect #rows for table t1.
 MariaDB-5.3: this is expected to go away when FROM subquery optimizations are pushed
 explain select * from v1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	4	
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
 2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	4	Using filesort
 drop view v1;
 drop table t1;

mysql-test/suite/vcol/r/vcol_view_myisam.result

@@ -107,7 +107,7 @@ MariaDB-5.3: the following EXPLAIN produces incorrect #rows for table t1.
 MariaDB-5.3: this is expected to go away when FROM subquery optimizations are pushed
 explain select * from v1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	4	
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
 2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	4	Using filesort
 drop view v1;
 create view v1 as select c+1 from t1 order by 1 desc limit 2;
@@ -119,7 +119,7 @@ MariaDB-5.3: the following EXPLAIN produces incorrect #rows for table t1.
 MariaDB-5.3: this is expected to go away when FROM subquery optimizations are pushed
 explain select * from v1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	4	
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
 2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	4	Using filesort
 drop view v1;
 drop table t1;

mysql-test/t/derived_view.test

@@ -1277,6 +1277,20 @@ ORDER BY CONCAT(alias2.col_varchar_nokey);
 set max_heap_table_size= @tmp_882994;
 drop table t1,t2,t3;
 
+--echo #
+--echo # LP bug #917990: Bad estimate of #rows for derived table with LIMIT
+--echo #
+
+CREATE TABLE t1 (a int);
+INSERT INTO t1 VALUES
+  (8), (3), (4), (7), (9), (5), (1), (2);
+
+SELECT * FROM (SELECT * FROM t1 LIMIT 3) t;
+EXPLAIN
+SELECT * FROM (SELECT * FROM t1 LIMIT 3) t;
+
+DROP TABLE t1;
+
 # The following command must be the last one the file 
 set optimizer_switch=@exit_optimizer_switch;
 set join_cache_level=@exit_join_cache_level;

sql/sql_derived.cc

@@ -753,6 +753,7 @@ bool mysql_derived_optimize(THD *thd, LEX *lex, TABLE_LIST *derived)
     if (!derived->is_merged_derived())
     {
       JOIN *join= first_select->join;
+      unit->set_limit(first_select);
       unit->optimized= TRUE;
       if ((res= join->optimize()))
         goto err;

sql/sql_select.cc

@@ -3581,6 +3581,7 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
       for (i= 0; i < join->table_count ; i++)
         records*= join->best_positions[i].records_read ?
                   (ha_rows)join->best_positions[i].records_read : 1;
+      set_if_smaller(records, unit->select_limit_cnt);
       join->select_lex->increase_derived_records(records);
     }
   }