149 lines
7.1 KiB
Markdown
149 lines
7.1 KiB
Markdown
---
|
|
stage: Data Stores
|
|
group: Database
|
|
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/product/ux/technical-writing/#assignments
|
|
---
|
|
|
|
# Database Lab and Postgres.ai
|
|
|
|
Internal users at GitLab have access to the Database Lab Engine (DLE) and
|
|
[postgres.ai](https://console.postgres.ai/) for testing performance of database queries
|
|
on replicated production data. Unlike a typical read-only production replica, in the DLE you can
|
|
also create, update, and delete rows. You can also test the performance of
|
|
schema changes, like additional indexes or columns, in an isolated copy of production data.
|
|
|
|
## Database Lab quick start
|
|
|
|
1. [Visit the console](https://console.postgres.ai/).
|
|
1. Select **Sign in with Google**. (Not GitLab, as you need Google SSO to connect with our project.)
|
|
1. After you sign in, select the GitLab organization and then visit "Ask Joe" in the sidebar.
|
|
1. Select the database you're testing against:
|
|
- Most queries for the GitLab project run against `gitlab-production-tunnel-pg12`.
|
|
- If the query is for a CI table, select `gitlab-production-ci`.
|
|
- If the query is for the container registry, select `gitlab-production-registry`.
|
|
1. Type `explain <Query Text>` in the chat box to get a plan.
|
|
|
|
## Access Database Lab Engine
|
|
|
|
Access to the DLE is helpful for:
|
|
|
|
- Database reviewers and maintainers.
|
|
- Engineers who work on merge requests that have large effects on databases.
|
|
|
|
To access the DLE's services, you can:
|
|
|
|
- Perform query testing in the Postgres.ai web console.
|
|
Employees access both services with their GitLab Google account. Query testing
|
|
provides `EXPLAIN` (analyze, buffers) plans for queries executed there.
|
|
- Migration testing by triggering a job as a part of a merge request.
|
|
- Direct `psql` access to DLE instead of a production replica. Available to authorized users only.
|
|
To request `psql` access, file an [access request](https://about.gitlab.com/handbook/business-technology/team-member-enablement/onboarding-access-requests/access-requests/#individual-or-bulk-access-request).
|
|
|
|
For more assistance, use the `#database` Slack channel.
|
|
|
|
NOTE:
|
|
If you need only temporary access to a production replica, instead of a Database Lab
|
|
clone, follow the runbook procedure for connecting to the
|
|
[database console with Teleport](https://gitlab.com/gitlab-com/runbooks/-/blob/master/docs/Teleport/Connect_to_Database_Console_via_Teleport.md).
|
|
This procedure is similar to [Rails console access with Teleport](https://gitlab.com/gitlab-com/runbooks/-/blob/master/docs/Teleport/Connect_to_Rails_Console_via_Teleport.md#how-to-use-teleport-to-connect-to-rails-console).
|
|
|
|
### Query testing
|
|
|
|
You can access Database Lab's query analysis features either:
|
|
|
|
- In [the Postgres.ai web console](https://console.postgres.ai/GitLab/joe-instances).
|
|
Shows only the commands you run.
|
|
|
|
#### Generate query plans
|
|
|
|
Query plans are an essential part of the database review process. These plans
|
|
enable us to decide quickly if a given query can be performant on GitLab.com.
|
|
Running the `explain` command generates an `explain` plan and a link to the Postgres.ai
|
|
console with more query analysis. For example, running `EXPLAIN SELECT * FROM application_settings`
|
|
does the following:
|
|
|
|
1. Runs `explain (analyze, buffers) select * from application_settings;` against a database clone.
|
|
1. Responds with timing and buffer details from the run.
|
|
1. Provides a [detailed, shareable report on the results](https://console.postgres.ai/shared/24d543c9-893b-4ff6-8deb-a8f902f85a53).
|
|
|
|
#### Making schema changes
|
|
|
|
Sometimes when testing queries, a contributor may realize that the query needs an index
|
|
or other schema change to make added queries more performant. To test the query, run the `exec` command.
|
|
For example, running this command:
|
|
|
|
```sql
|
|
exec CREATE INDEX on application_settings USING btree (instance_administration_project_id)
|
|
```
|
|
|
|
creates the specified index on the table. You can [test queries](#generate-query-plans) leveraging
|
|
the new index. `exec` does not return any results, only the time required to execute the query.
|
|
|
|
#### Reset the clone
|
|
|
|
After many changes, such as after a destructive query or an ineffective index,
|
|
you must start over. To reset your designated clone, run `reset`.
|
|
|
|
#### Checking indexes
|
|
|
|
Use Database Lab to check the status of an index with the meta-command `\d <index_name>`.
|
|
|
|
Caveats:
|
|
|
|
- Indexes are created in both the `main` and `ci` databases, so be sure to use the instance
|
|
that matches the table's `gitlab_schema`. For example, if the index is added to
|
|
[`ci_builds`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/db/docs/ci_builds.yml#L14),
|
|
use `gitlab-production-ci`.
|
|
- Database Lab typically has a small delay of a few hours. If more up-to-date information
|
|
is required, you can instead request access to a replica [via Teleport](https://gitlab.com/gitlab-com/runbooks/-/blob/master/docs/Teleport/Connect_to_Database_Console_via_Teleport.md)
|
|
|
|
For example: `\d index_design_management_designs_on_project_id` produces:
|
|
|
|
```plaintext
|
|
Index "public.index_design_management_designs_on_project_id"
|
|
Column | Type | Key? | Definition
|
|
------------+---------+------+------------
|
|
project_id | integer | yes | project_id
|
|
btree, for table "public.design_management_designs"
|
|
```
|
|
|
|
In the case of an invalid index, the output ends with `invalid`, like:
|
|
|
|
```plaintext
|
|
Index "public.index_design_management_designs_on_project_id"
|
|
Column | Type | Key? | Definition
|
|
------------+---------+------+------------
|
|
project_id | integer | yes | project_id
|
|
btree, for table "public.design_management_designs", invalid
|
|
```
|
|
|
|
If the index doesn't exist, JoeBot throws an error like:
|
|
|
|
```plaintext
|
|
ERROR: psql error: psql:/tmp/psql-query-932227396:1: error: Did not find any relation named "no_index".
|
|
```
|
|
|
|
### Migration testing
|
|
|
|
For information on testing migrations, review our
|
|
[database migration testing documentation](database_migration_pipeline.md).
|
|
|
|
### Access the console with `psql`
|
|
|
|
Team members with [`psql` access](#access-database-lab-engine), can gain direct access
|
|
to a clone via `psql`. Access to `psql` enables you to see data, not just metadata.
|
|
|
|
To connect to a clone using `psql`:
|
|
|
|
1. Create a clone from the [desired instance](https://console.postgres.ai/gitlab/instances/).
|
|
1. Provide a **Clone ID**: Something that uniquely identifies your clone, such as `yourname-testing-gitlabissue`.
|
|
1. Provide a **Database username** and **Database password**: Connects `psql` to your clone.
|
|
1. Select **Enable deletion protection** if you want to preserve your clone. Avoid selecting this option.
|
|
Clones are removed after 12 hours.
|
|
1. In the **Clone details** page of the Postgres.ai web interface, copy and run
|
|
the command to start SSH port forwarding for the clone.
|
|
1. In the **Clone details** page of the Postgres.ai web interface, copy and run the `psql` connection string.
|
|
Use the password provided at setup and set the `dbname` to `gitlabhq_dblab` (or check what databases are available by using `psql -l` with the same query string but `dbname=postgres`).
|
|
|
|
After you connect, use clone like you would any `psql` console in production, but with
|
|
the added benefit and safety of an isolated writeable environment.
|