34 lines
1.4 KiB
Markdown
34 lines
1.4 KiB
Markdown
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# Delete existing migrations
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When removing existing migrations from the GitLab project, you have to take into account
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the possibility of the migration already been included in past releases or in the current release, and thus already executed on GitLab.com and/or in self-hosted instances.
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Because of it, it's not possible to delete existing migrations, as that could lead to:
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- Schema inconsistency, as changes introduced into the database were not rollbacked properly.
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- Leaving a record on the `schema_versions` table, that points out to migration that no longer exists on the codebase.
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Instead of deleting we can opt for disabling the migration.
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## Pre-requisites to disable a migration
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Migrations can be disabled if:
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- They caused a timeout or general issue on GitLab.com.
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- They are obsoleted, e.g. changes are not necessary due to a feature change.
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- Migration is a data migration only, i.e. the migration does not change the database schema.
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## How to disable a data migration?
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In order to disable a migration, the following steps apply to all types of migrations:
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1. Turn the migration into a noop by removing the code inside `#up`, `#down`
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or `#perform` methods, and adding `#no-op` comment instead.
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1. Add a comment explaining why the code is gone.
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Disabling migrations requires explicit approval of Database Maintainer.
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## Examples
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- [Disable scheduling of productivity analytics](https://gitlab.com/gitlab-org/gitlab/merge_requests/17253)
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