# Pt-osc on mysql version 5.7

**URL:** <https://forums.percona.com/t/pt-osc-on-mysql-version-5-7/23823>\
**Category:** Percona Server for MySQL 5.7\
**Tags:** percona\
**Created:** [July 22, 2023, 6:49am UTC](https://forums.percona.com/t/pt-osc-on-mysql-version-5-7/23823 "2023-07-22T06:49:08Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![virin\_t](https://avatars.discourse-cdn.com/v4/letter/v/b38774/32.png) [@virin\_t](https://forums.percona.com/u/virin_t)\
**Post date:** [July 22, 2023, 6:49am UTC](https://forums.percona.com/t/pt-osc-on-mysql-version-5-7/23823/1 "2023-07-22T06:49:08Z")

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Hi, I did a pt-osc for a table, as pre check I can confirm that there no triggers on table using  
SELECT TRIGGER\_NAME FROM INFORMATION\_SCHEMA.TRIGGERS WHERE TRIGGER\_SCHEMA=‘’ AND event\_object\_table=‘

’;

However, after executing I found the message in the end showing as  
2023-07-21T23:41:44 Dropping triggers…  
2023-07-21T23:41:44 Dropped triggers OK.

Is this expected even when there are no triggers on the given table?

2023-07-21T23:41:44 Creating triggers…  
2023-07-21T23:41:44 Created triggers OK.  
2023-07-21T23:41:44 Copying approximately 43 rows…  
2023-07-21T23:41:44 Copied rows OK.  
2023-07-21T23:41:44 Analyzing new table…  
2023-07-21T23:41:44 Swapping tables…  
2023-07-21T23:41:44 Swapped original and new tables OK.  
Not dropping old table because --no-drop-old-table was specified.  
2023-07-21T23:41:44 Dropping triggers…  
2023-07-21T23:41:44 Dropped triggers OK.

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<div class="post-metadata">

**Author:** ![kedarpercona](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/kedarpercona/32/809_2.png) [@kedarpercona](https://forums.percona.com/u/kedarpercona)\
**Post date:** [July 22, 2023, 7:05am UTC](https://forums.percona.com/t/pt-osc-on-mysql-version-5-7/23823/2 "2023-07-22T07:05:30Z")

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Hello @virin_t,

In the pre-checks query, I hope you are obfuscating the table names and not really provided them empty:

```auto
SELECT TRIGGER_NAME FROM INFORMATION_SCHEMA.TRIGGERS WHERE TRIGGER_SCHEMA='' AND event_object_table='';

```

You should mention TRIGGER\_SCHEMA and event\_object\_table values in order to get correct response.

About “dropping triggers”, they were the triggers that pt-osc had created to transfer the data from OLD table to the NEW table. You probably should read the output from the top and you will also note the “creating triggers” note.

I’d invite you to read the [pt-osc documentation](https://docs.percona.com/percona-toolkit/pt-online-schema-change.html#description) about the usage of triggers/how it works.

Thanks,  
K

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<div class="post-metadata">

**Author:** ![virin\_t](https://avatars.discourse-cdn.com/v4/letter/v/b38774/32.png) [@virin\_t](https://forums.percona.com/u/virin_t)\
**Post date:** [July 22, 2023, 7:06am UTC](https://forums.percona.com/t/pt-osc-on-mysql-version-5-7/23823/3 "2023-07-22T07:06:57Z")

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Thank you Kedar, that makes sense.

yeah, I did mention TRIGGER\_SCHEMA and event\_object\_table , just did have them here.  
I went neurotic and created this.