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diff --git a/doc/development/migration_style_guide.md b/doc/development/migration_style_guide.md index c9b59ba66b5..4a1d4389ceb 100644 --- a/doc/development/migration_style_guide.md +++ b/doc/development/migration_style_guide.md @@ -90,6 +90,14 @@ Keep in mind that all durations should be measured against GitLab.com. | Post-deployment migrations | `<= 10 minutes` | A valid exception are schema changes, since they must not happen in background migrations. | | Background migrations | `> 10 minutes` | Since these are suitable for larger tables, it's not possible to set a precise timing guideline, however, any single query must stay below [`1 second` execution time](query_performance.md#timing-guidelines-for-queries) with cold caches. | +## Decide which database to target + +GitLab connects to two different Postgres databases: `main` and `ci`. This split can affect migrations +as they may run on either or both of these databases. + +Read [Migrations for Multiple databases](database/migrations_for_multiple_databases.md) to understand if or how +a migration you add should account for this. + ## Create a regular schema migration To create a migration you can use the following Rails generator: |