From 8e89ff67fa25b47b4b509b7502030117a2e430ed Mon Sep 17 00:00:00 2001
From: Andreas Brandl <abrandl@gitlab.com>
Date: Tue, 1 Sep 2020 13:12:05 +0200
Subject: [PATCH] Add documentation for managing PG extensions
This adds a document to describe the background for managing PG
extensions.
---
doc/install/postgresql_extensions.md | 76 ++++++++++++++++++++++++
doc/install/requirements.md | 7 +--
doc/update/README.md | 1 +
lib/gitlab/database/migration_helpers.rb | 4 +-
4 files changed, 81 insertions(+), 7 deletions(-)
create mode 100644 doc/install/postgresql_extensions.md
diff --git a/doc/install/postgresql_extensions.md b/doc/install/postgresql_extensions.md
new file mode 100644
index 0000000000000..4156d72097d8a
--- /dev/null
+++ b/doc/install/postgresql_extensions.md
@@ -0,0 +1,76 @@
+---
+last_updated: 2020-09-01
+---
+
+# Managing PostgreSQL extensions
+
+This guide documents how to manage PostgreSQL extensions for installations with an external
+PostgreSQL database.
+
+GitLab requires certain extensions to be installed into the GitLab database. For example,
+GitLab relies on `pg_trgm` and the `btree_gist` extensions.
+
+In order to install extensions, PostgreSQL requires the user to have superuser privileges.
+Typically, the GitLab database user is not a superuser. Therefore, regular database migrations
+cannot be used in installing extensions and instead, extensions have to be installed manually
+prior to upgrading GitLab to a newer version.
+
+## Installing PostgreSQL extensions manually
+
+In order to install a PostgreSQL extension, this procedure should be followed:
+
+1. Connect to the GitLab PostgreSQL database using a superuser, for example:
+
+ ```shell
+ sudo gitlab-psql -d gitlabhq_production
+ ```
+
+1. Install the extension (`btree_gist` in this example) using [`CREATE EXTENSION`](https://www.postgresql.org/docs/11/sql-createextension.html):
+
+ ```sql
+ CREATE EXTENSION IF NOT EXISTS btree_gist
+ ```
+
+1. Verify installed extensions:
+
+ ```shell
+ gitlabhq_production=# \dx
+ List of installed extensions
+ Name | Version | Schema | Description
+ ------------+---------+------------+-------------------------------------------------------------------
+ btree_gist | 1.5 | public | support for indexing common datatypes in GiST
+ pg_trgm | 1.4 | public | text similarity measurement and index searching based on trigrams
+ plpgsql | 1.0 | pg_catalog | PL/pgSQL procedural language
+ (3 rows)
+ ```
+
+On some systems you may need to install an additional package (for example,
+`postgresql-contrib`) for certain extensions to become available.
+
+## A typical migration failure scenario
+
+The following is an example of a situation when the extension hasn't been installed before running migrations.
+In this scenario, the database migration fails to create the extension `btree_gist` because of insufficient
+privileges.
+
+```shell
+== 20200515152649 EnableBtreeGistExtension: migrating =========================
+-- execute("CREATE EXTENSION IF NOT EXISTS btree_gist")
+
+GitLab requires the PostgreSQL extension 'btree_gist' installed in database 'gitlabhq_production', but
+the database user is not allowed to install the extension.
+
+You can either install the extension manually using a database superuser:
+
+ CREATE EXTENSION IF NOT EXISTS btree_gist
+
+Or, you can solve this by logging in to the GitLab database (gitlabhq_production) using a superuser and running:
+
+ ALTER regular WITH SUPERUSER
+
+This query will grant the user superuser permissions, ensuring any database extensions
+can be installed through migrations.
+```
+
+In order to recover from this situation, the extension needs to be installed manually using a superuser, and
+the database migration (or GitLab upgrade) can be retried afterwards.
diff --git a/doc/install/requirements.md b/doc/install/requirements.md
index 7cfccc798d0f6..b3862cf743465 100644
--- a/doc/install/requirements.md
+++ b/doc/install/requirements.md
@@ -143,11 +143,8 @@ GitLab version | Minimum PostgreSQL version
12.10 | 11
13.0 | 11
-You must also ensure the `pg_trgm` and `btree_gist` extensions are loaded into every
-GitLab database. These extensions [can be enabled](https://www.postgresql.org/docs/11/sql-createextension.html) using a PostgreSQL super user.
-
-On some systems you may need to install an additional package (for example,
-`postgresql-contrib`) for this extension to become available.
+You must also ensure the `pg_trgm` and `btree_gist` extensions are [loaded into every
+GitLab database](postgresql_extensions.html).
NOTE: **Note:**
Support for [PostgreSQL 9.6 and 10 has been removed in GitLab 13.0](https://about.gitlab.com/releases/2020/05/22/gitlab-13-0-released/#postgresql-11-is-now-the-minimum-required-version-to-install-gitlab) so that GitLab can benefit from PostgreSQL 11 improvements, such as partitioning. For the schedule of transitioning to PostgreSQL 12, see [the related epic](https://gitlab.com/groups/gitlab-org/-/epics/2184).
diff --git a/doc/update/README.md b/doc/update/README.md
index 85fc4363673b0..a7f7aaf58879c 100644
--- a/doc/update/README.md
+++ b/doc/update/README.md
@@ -310,3 +310,4 @@ for more information.
- [Restoring from backup after a failed upgrade](restore_after_failure.md)
- [Upgrading PostgreSQL Using Slony](upgrading_postgresql_using_slony.md), for
upgrading a PostgreSQL database with minimal downtime.
+- [Managing PostgreSQL extensions](../install/postgresql_extensions.md)
diff --git a/lib/gitlab/database/migration_helpers.rb b/lib/gitlab/database/migration_helpers.rb
index e8378e923ffd3..b62b6e20dd582 100644
--- a/lib/gitlab/database/migration_helpers.rb
+++ b/lib/gitlab/database/migration_helpers.rb
@@ -1234,7 +1234,7 @@ def create_extension(extension)
This query will grant the user superuser permissions, ensuring any database extensions
can be installed through migrations.
- For more information please refer to doc/install/postgresql_extensions.md.
+ For more information, refer to https://docs.gitlab.com/ee/install/postgresql_extensions.html.
MSG
raise
@@ -1263,7 +1263,7 @@ def drop_extension(extension)
This query will grant the user superuser permissions, ensuring any database extensions
can be dropped through migrations.
- For more information please refer to doc/install/postgresql_extensions.md.
+ For more information, refer to https://docs.gitlab.com/ee/install/postgresql_extensions.html.
MSG
raise
--
GitLab