[MDEV-9390] Function found_rows() gives incorrect result where the previous SELECT contains ORDER BY clause Created: 2016-01-11  Updated: 2016-02-15  Resolved: 2016-02-15

Status: Closed
Project: MariaDB Server
Component/s: Optimizer
Affects Version/s: 10.0, 10.1
Fix Version/s: 10.0.24, 10.1.12

Type: Bug Priority: Major
Reporter: Dylan Su Assignee: Sergei Golubchik
Resolution: Fixed Votes: 1
Labels: None

Sprint: 10.0.24

 Description   

Output:
=====

mysql> create table t1(c1 int);
Query OK, 0 rows affected (0.01 sec)
 
mysql> insert into t1 values(1),(2),(3),(4),(5);
Query OK, 5 rows affected (0.00 sec)
Records: 5  Duplicates: 0  Warnings: 0
 
mysql> select * from t1 order by c1 limit 2,1;
+------+
| c1   |
+------+
|    3 |
+------+
1 row in set (0.00 sec)
 
mysql> select found_rows();
+--------------+
| found_rows() |
+--------------+
|            5 |
+--------------+
1 row in set (0.00 sec)
 
mysql> select version();
+-----------------+
| version()       |
+-----------------+
| 10.1.10-MariaDB |
+-----------------+
1 row in set (0.00 sec)
 

Repeat:
=====

drop table if exists t1;
create table t1(c1 int);
insert into t1 values(1),(2),(3),(4),(5);
select * from t1 order by c1 limit 2,1;
select found_rows();
 

Problem:
=====
3 is expected.



 Comments   
Comment by Elena Stepanova [ 2016-01-12 ]

Thanks for the report and the test case.

The problem appeared in 10.0 tree with this revision:

commit fde6ee61bbdeb051a169aac8da56e24bf2accdce
Author: Sergei Golubchik <sergii@pisem.net>
Date:   Thu Jun 5 15:59:41 2014 +0200
 
    revert the fix for MDEV-5898, restore the fix for MDEV-5549.
    simplify test case for MDEV-5898

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