# 延迟的 columndropper 问题

**URL:** https://meta.discourse.org/t/delayed-columndropper-issues/98339
**Category:** Support
**Created:** [2018年九月29日 11:40 UTC](https://meta.discourse.org/t/delayed-columndropper-issues/98339 "2018-09-29T11:40:03Z")
**Posts on this page:** 1
**Showing post:** 6

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### Author: ![david](https://sea3.discourse-cdn.com/meta/user_avatar/meta.discourse.org/david/32/157490_2.png) [@david](https://meta.discourse.org/u/david)
#### Post date: [2021年六月14日 08:48 UTC](https://meta.discourse.org/t/delayed-columndropper-issues/98339/6 "2021-06-14T08:48:18Z")

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> [@Introducing Post Deployment Migration](https://meta.discourse.org/t/introducing-post-deployment-migration/98974):
>
> As of [https://github.com/discourse/discourse/commit/40fa96777ddad4698df20d6b8a61afcf87743ed7](https://github.com/discourse/discourse/commit/40fa96777ddad4698df20d6b8a61afcf87743ed7), we’re moving away from [our delayed drop pattern](https://github.com/discourse/discourse/blob/9bbc1ae7b2ed9bd7e73f3ec9de6cf12e09178612/db/fixtures/000_delayed_drops.rb) to remove a column from a table in the database. Inspired by [Gitlab’s pattern of post deployment migration](https://docs.gitlab.com/ee/development/post_deployment_migrations.html), we’ve added the ability to generate and run migrations that can be run after a deployment. SKIP\_POST\_DEPLOYMENT\_MIGRATIONS=1 rake db:migrate -\> deploy app servers SKIP\_POST\_DEPLOYMENT\_MIGRATIONS=0 rake db:migrate To generate a post deployment migra…

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