# decreased row count after an alter table

**URL:** <https://forums.percona.com/t/decreased-row-count-after-an-alter-table/1584>\
**Category:** Other MySQL® Questions\
**Created:** [December 18, 2010, 7:59pm UTC](https://forums.percona.com/t/decreased-row-count-after-an-alter-table/1584 "2010-12-18T19:59:46Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Soham](https://avatars.discourse-cdn.com/v4/letter/s/7ea924/32.png) [@Soham](https://forums.percona.com/u/Soham)\
**Post date:** [December 18, 2010, 7:59pm UTC](https://forums.percona.com/t/decreased-row-count-after-an-alter-table/1584/1 "2010-12-18T19:59:46Z")

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I ran an alter table (increased index length on a varchar column from 5 to 10 characters) on a large table (several million)rows.

A show-table-status after the alter shows about 10% decreased row count. I spot-checked and it doesn’t seem like there is any actual data loss.

Wondering what could be happening?

Running Mysql 5.0.60, with InnoDB.

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**Author:** ![xaprb](https://avatars.discourse-cdn.com/v4/letter/x/49beb7/32.png) [@xaprb](https://forums.percona.com/u/xaprb)\
**Post date:** [December 18, 2010, 8:26pm UTC](https://forums.percona.com/t/decreased-row-count-after-an-alter-table/1584/2 "2010-12-18T20:26:02Z")

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InnoDB’s row statistics are only approximate estimates, so it’s nothing to worry about.

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<div class="post-metadata">

**Author:** ![Soham](https://avatars.discourse-cdn.com/v4/letter/s/7ea924/32.png) [@Soham](https://forums.percona.com/u/Soham)\
**Post date:** [December 18, 2010, 9:44pm UTC](https://forums.percona.com/t/decreased-row-count-after-an-alter-table/1584/3 "2010-12-18T21:44:50Z")

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Thanks!

Wondering why is that? And why would the number change (so dramatically) with an alter-table?