# Pt-osc adding foreign keys adds "\_" and "\_ \_" to the foreign key names

**URL:** <https://forums.percona.com/t/pt-osc-adding-foreign-keys-adds-and-to-the-foreign-key-names/29214>\
**Category:** MySQL & MariaDB\
**Created:** [March 19, 2024, 10:56am UTC](https://forums.percona.com/t/pt-osc-adding-foreign-keys-adds-and-to-the-foreign-key-names/29214 "2024-03-19T10:56:03Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Mohitsh](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Mohitsh](https://forums.percona.com/u/Mohitsh)\
**Post date:** [March 19, 2024, 10:56am UTC](https://forums.percona.com/t/pt-osc-adding-foreign-keys-adds-and-to-the-foreign-key-names/29214/1 "2024-03-19T10:56:03Z")

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Hi Team,

I have a query regarding Pt-osc. My question is regarding using PT-OSC to drop Foreign Key.  
When i drop the First foreign key constraint on a table having 2 foreign key’s, PT-osc adds an \_ to the already existing second fk, And when am adding a new FK constraint pt-osc is adding \_ \_ to the already existing Second Foreign key constraint.  
Is this the expected behaviour form the tool? Am using the latest version of percona-toolkit.

Thanks  
Mohit S

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**Author:** ![matthewb](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/matthewb/32/34_2.png) [@matthewb](https://forums.percona.com/u/matthewb)\
**Post date:** [March 19, 2024, 2:00pm UTC](https://forums.percona.com/t/pt-osc-adding-foreign-keys-adds-and-to-the-foreign-key-names/29214/2 "2024-03-19T14:00:57Z")

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Hi @Mohitsh,  
Yes, pt-osc blindly adds `_` as a way to prevent conflict names.

> using PT-OSC to drop Foreign Key.

You don’t need PT-OSC for this. Dropping keys is a background operation since MySQL 5.6.