# Why pt-table-checksum diffs 0 while  my master and slave are certainly  different?

**URL:** <https://forums.percona.com/t/why-pt-table-checksum-diffs-0-while-my-master-and-slave-are-certainly-different/4252>\
**Category:** Percona Toolkit\
**Created:** [June 8, 2015, 9:32pm UTC](https://forums.percona.com/t/why-pt-table-checksum-diffs-0-while-my-master-and-slave-are-certainly-different/4252 "2015-06-08T21:32:01Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![leafonsword](https://avatars.discourse-cdn.com/v4/letter/l/85f322/32.png) [@leafonsword](https://forums.percona.com/u/leafonsword)\
**Post date:** [June 8, 2015, 9:32pm UTC](https://forums.percona.com/t/why-pt-table-checksum-diffs-0-while-my-master-and-slave-are-certainly-different/4252/1 "2015-06-08T21:32:01Z")

</div>

```auto

pt-table-checksum ：2.2.14
MySQL：5.6.19
Binlog：row

```

```auto

Master：
mysql> select * from test.gf;
+------+
| id |
+------+
| 2 |
| 5 |
| 7 |
+------+
Slave:

mysql> select * from test.gf;
+------+
| id |
+------+
| 7 |
+------+

```

So master and slave are certainly different，but running pt-table-checksum shows no difference:

```auto

./pt-table-checksum h=localhost,u=root,p=PASSWORD,P=3306
......
other table checking result
......
06-09T10:55:31 0 0 3 1 0 0.003 test.gf

```

And percona.checksums table in slave shows difference crc:

```auto

select * from percona.checksums;
......
other output rows
......
| test | gf | 1 | 0.000625 | NULL | NULL | NULL | [B]46156dca [/B]| 1 | [B]435a7b4f [/B]| 3 | 2015-06-09 10:55:31 |

```

My question is since percona.checksums table in slave shows that crc checking diffs in master and slave ,why pt-table-checksum report’s diffs column shows 0?

---

<div class="post-metadata">

**Author:** ![leafonsword](https://avatars.discourse-cdn.com/v4/letter/l/85f322/32.png) [@leafonsword](https://forums.percona.com/u/leafonsword)\
**Post date:** [June 9, 2015, 9:20pm UTC](https://forums.percona.com/t/why-pt-table-checksum-diffs-0-while-my-master-and-slave-are-certainly-different/4252/2 "2015-06-09T21:20:43Z")

</div>

I found the reason, because DSN’s username(root) just could login to master but couldn’t login to slave, but shouldn’t pt-table-checksum give an alert other than just showing diffs 0?

---

<div class="post-metadata">

**Author:** ![scott.nemes](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/scott.nemes/32/5_2.png) [@scott.nemes](https://forums.percona.com/u/scott.nemes)\
**Post date:** [June 10, 2015, 9:30am UTC](https://forums.percona.com/t/why-pt-table-checksum-diffs-0-while-my-master-and-slave-are-certainly-different/4252/3 "2015-06-10T09:30:23Z")

</div>

Hi leafonsword;

That would probably be worth submitting as a bug for logging improvement.

[url][https://bugs.launchpad.net/percona-toolkit[/url]](https://bugs.launchpad.net/percona-toolkit%5B/url%5D)

-Scott