# pt-online-schema-change and foreign key constraints

**URL:** <https://forums.percona.com/t/pt-online-schema-change-and-foreign-key-constraints/4702>\
**Category:** Percona Toolkit\
**Created:** [February 7, 2016, 12:38pm UTC](https://forums.percona.com/t/pt-online-schema-change-and-foreign-key-constraints/4702 "2016-02-07T12:38:40Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Edward\_Hibbert](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/edward_hibbert/32/993_2.png) [@Edward\_Hibbert](https://forums.percona.com/u/Edward_Hibbert)\
**Post date:** [February 7, 2016, 12:38pm UTC](https://forums.percona.com/t/pt-online-schema-change-and-foreign-key-constraints/4702/1 "2016-02-07T12:38:40Z")

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This is a great tool. I’m using it with --alter-foreign-keys-method=rebuild\_constraints, because my reading of the help is that this is the only really safe option (please correct me if this is wrong).

However this can cause a rebuild of other tables - which can on occasion be a worse problem for availability than not using pt-online-schema-change at all, if the second table is large, or if there are multiple tables to rebuild.

I was wondering if it is possible for this tool to work in a way which also rebuilds those other tables in a nicely available way?

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**Author:** ![Edward\_Hibbert](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/edward_hibbert/32/993_2.png) [@Edward\_Hibbert](https://forums.percona.com/u/Edward_Hibbert)\
**Post date:** [March 15, 2016, 1:24pm UTC](https://forums.percona.com/t/pt-online-schema-change-and-foreign-key-constraints/4702/2 "2016-03-15T13:24:11Z")

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Bump. Maybe my question isn’t clear?