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Diffstat (limited to 'doc/development/what_requires_downtime.md')
| -rw-r--r-- | doc/development/what_requires_downtime.md | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/doc/development/what_requires_downtime.md b/doc/development/what_requires_downtime.md index 9063fb867e2..18a2e17967a 100644 --- a/doc/development/what_requires_downtime.md +++ b/doc/development/what_requires_downtime.md @@ -1,3 +1,9 @@ +--- +stage: Enablement +group: Database +info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers +--- + # What requires downtime? When working with a database certain operations can be performed without taking @@ -88,6 +94,8 @@ renaming. For example class RenameUsersUpdatedAtToUpdatedAtTimestamp < ActiveRecord::Migration[4.2] include Gitlab::Database::MigrationHelpers + DOWNTIME = false + disable_ddl_transaction! def up @@ -100,13 +108,12 @@ class RenameUsersUpdatedAtToUpdatedAtTimestamp < ActiveRecord::Migration[4.2] end ``` -This will take care of renaming the column, ensuring data stays in sync, copying -over indexes and foreign keys, etc. +This will take care of renaming the column, ensuring data stays in sync, and +copying over indexes and foreign keys. -NOTE: **Note:** -If a column contains 1 or more indexes that do not contain the name of -the original column, the above procedure will fail. In this case you will first -need to rename these indexes. +If a column contains one or more indexes that don't contain the name of the +original column, the previously described procedure will fail. In that case, +you'll first need to rename these indexes. ### Step 2: Add A Post-Deployment Migration @@ -131,7 +138,6 @@ class CleanupUsersUpdatedAtRename < ActiveRecord::Migration[4.2] end ``` -NOTE: **Note:** If you're renaming a [large table](https://gitlab.com/gitlab-org/gitlab/-/blob/master/rubocop/rubocop-migrations.yml#L3), please carefully consider the state when the first migration has run but the second cleanup migration hasn't been run yet. With [Canary](https://gitlab.com/gitlab-com/gl-infra/readiness/-/tree/master/library/canary/) it is possible that the system runs in this state for a significant amount of time. @@ -142,7 +148,7 @@ done without requiring downtime. However, this does require that any application changes are deployed _first_. Thus, changing the constraints of a column should happen in a post-deployment migration. -NOTE: Avoid using `change_column` as it produces an inefficient query because it re-defines +Avoid using `change_column` as it produces an inefficient query because it re-defines the whole column type. You can check the following guides for each specific use case: |