# Could pt-archiver use a non-unique key as chunk index?

**URL:** <https://forums.percona.com/t/could-pt-archiver-use-a-non-unique-key-as-chunk-index/18620>\
**Category:** Percona Toolkit\
**Created:** [November 17, 2022, 6:33am UTC](https://forums.percona.com/t/could-pt-archiver-use-a-non-unique-key-as-chunk-index/18620 "2022-11-17T06:33:50Z")\
**Posts on this page:** 1\
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**Author:** ![Luke03011](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/luke03011/32/16409_2.png) [@Luke03011](https://forums.percona.com/u/Luke03011)\
**Post date:** [January 12, 2024, 2:58am UTC](https://forums.percona.com/t/could-pt-archiver-use-a-non-unique-key-as-chunk-index/18620/3 "2024-01-12T02:58:20Z")

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Sorry it’s a long time when I post this ticket. But as the `idx_c2` actually contains the primary key `id` internally(In fact every secondary index will contain the primary key columns to make the indexed value is unique in the secondary index tree). So I am curious why `pt-archiver` does not use that part to guarantee the correctness.

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