# add generated virtual column still copy data

**URL:** <https://forums.percona.com/t/add-generated-virtual-column-still-copy-data/5449>\
**Category:** Other MySQL® Questions\
**Created:** [February 27, 2017, 4:29pm UTC](https://forums.percona.com/t/add-generated-virtual-column-still-copy-data/5449 "2017-02-27T16:29:31Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![baoxiao](https://avatars.discourse-cdn.com/v4/letter/b/f6c823/32.png) [@baoxiao](https://forums.percona.com/u/baoxiao)\
**Post date:** [February 27, 2017, 4:29pm UTC](https://forums.percona.com/t/add-generated-virtual-column-still-copy-data/5449/1 "2017-02-27T16:29:31Z")

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When run the below query it take long time  
alter table record\_log add column record\_key varchar(255) AS (md5(concat(record\_time,record\_campId))) VIRTUAL ;  
show processlist show it copy data to tmp table, suppose it will done in place with data copy

34 | root | localhost | record | Query | 26 | copy to tmp table | alter table record\_log add column record\_key varchar(32) AS (md5(concat(record\_time,reco | 0 |

MySQL version is 5.7.13-6-log Percona Server (GPL), Release 6, Revision e3d58bb

Thanks