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+---
+stage: Enablement
+group: Sharding
+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/#assignments
+---
+
+# Multiple Databases
+
+In order to scale GitLab, the GitLab application database
+will be [decomposed into multiple
+databases](https://gitlab.com/groups/gitlab-org/-/epics/6168).
+
+## CI Database
+
+Support for configuring the GitLab Rails application to use a distinct
+database for CI tables was added in [GitLab
+14.1](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64289). This
+feature is still under development, and is not ready for production use.
+
+By default, GitLab is configured to use only one main database. To
+opt-in to use a main database, and CI database, modify the
+`config/database.yml` file to have a `primary` and a `ci` database
+configurations. For example, given a `config/database.yml` like below:
+
+```yaml
+development:
+  adapter: postgresql
+  encoding: unicode
+  database: gitlabhq_development
+  host: /path/to/gdk/postgresql
+  pool: 10
+  prepared_statements: false
+  variables:
+    statement_timeout: 120s
+
+test: &test
+  adapter: postgresql
+  encoding: unicode
+  database: gitlabhq_test
+  host: /path/to/gdk/postgresql
+  pool: 10
+  prepared_statements: false
+  variables:
+    statement_timeout: 120s
+```
+
+Edit the `config/database.yml` to look like this:
+
+```yaml
+development:
+  primary:
+    adapter: postgresql
+    encoding: unicode
+    database: gitlabhq_development
+    host: /path/to/gdk/postgresql
+    pool: 10
+    prepared_statements: false
+    variables:
+      statement_timeout: 120s
+  ci:
+    adapter: postgresql
+    encoding: unicode
+    database: gitlabhq_development_ci
+    migrations_paths: db/ci_migrate
+    host: /path/to/gdk/postgresql
+    pool: 10
+    prepared_statements: false
+    variables:
+      statement_timeout: 120s
+
+test: &test
+  primary:
+    adapter: postgresql
+    encoding: unicode
+    database: gitlabhq_test
+    host: /path/to/gdk/postgresql
+    pool: 10
+    prepared_statements: false
+    variables:
+      statement_timeout: 120s
+  ci:
+    adapter: postgresql
+    encoding: unicode
+    database: gitlabhq_test_ci
+    migrations_paths: db/ci_migrate
+    host: /path/to/gdk/postgresql
+    pool: 10
+    prepared_statements: false
+    variables:
+      statement_timeout: 120s
+```
+
+Note that we use `primary` in the `config/database.yml` to refer to the main
+database. This is to match the default name Rails has.
+
+### Migrations
+
+Any migrations that affect `Ci::ApplicationRecord` models
+and their tables must be placed in two directories for now:
+
+- `db/migrate`
+- `db/ci_migrate`
+
+We aim to keep the schema for both tables the same across both databases.