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author | GitLab Bot <gitlab-bot@gitlab.com> | 2022-06-03 15:09:05 +0300 |
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committer | GitLab Bot <gitlab-bot@gitlab.com> | 2022-06-03 15:09:05 +0300 |
commit | c74f702c747d1b14c3ddea951ceb7970941dc8f5 (patch) | |
tree | 618149e281728f2cfae469dddd2aafa76ed85843 /doc/development/migration_style_guide.md | |
parent | 6be8ed5a9529d37f1512549f62db1e44961a4fc0 (diff) |
Add latest changes from gitlab-org/gitlab@master
Diffstat (limited to 'doc/development/migration_style_guide.md')
-rw-r--r-- | doc/development/migration_style_guide.md | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/doc/development/migration_style_guide.md b/doc/development/migration_style_guide.md index 2359f0fc2d1..c9b59ba66b5 100644 --- a/doc/development/migration_style_guide.md +++ b/doc/development/migration_style_guide.md @@ -898,6 +898,44 @@ def down end ``` +## Dropping a sequence + +> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/88387) in GitLab 15.1. + +Dropping a sequence is uncommon, but you can use the `drop_sequence` method provided by the database team. + +Under the hood, it works like this: + +Remove a sequence: + +- Remove the default value if the sequence is actually used. +- Execute `DROP SEQUENCE`. + +Re-add a sequence: + +- Create the sequence, with the possibility of specifying the current value. +- Change the default value of the column. + +A Rails migration example: + +```ruby +class DropSequenceTest < Gitlab::Database::Migration[2.0] + def up + drop_sequence(:ci_pipelines_config, :pipeline_id, :ci_pipelines_config_pipeline_id_seq) + end + + def down + default_value = Ci::Pipeline.maximum(:id) + 10_000 + + add_sequence(:ci_pipelines_config, :pipeline_id, :ci_pipelines_config_pipeline_id_seq, default_value) + end +end +``` + +NOTE: +`add_sequence` should be avoided for columns with foreign keys. +Adding sequence to these columns is **only allowed** in the down method (restore previous schema state). + ## Integer column type By default, an integer column can hold up to a 4-byte (32-bit) number. That is |