Specify the required postgres extensions

Explicitly state the GitLab version where
the required postgres extensions were introduced.

doc/install/postgresql_extensions.md

@@ -9,8 +9,12 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 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.
+The following extensions are required to be installed into the GitLab database.
+
+| Extension    | Minimum GitLab version |
+| ------------ | ---------------------- |
+| `pg_trgm`    | 8.6                    |
+| `btree_gist` | 13.1                   |
 
 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

doc/install/requirements.md

@@ -152,16 +152,22 @@ MySQL/MariaDB are advised to [migrate to PostgreSQL](../update/mysql_to_postgres
 The server running PostgreSQL should have _at least_ 5-10 GB of storage
 available, though the exact requirements [depend on the number of users](../administration/reference_architectures/index.md).
 
-We highly recommend users to use the minimum PostgreSQL versions specified below as these are the versions used for development and testing.
+We highly recommend users to use the minimum PostgreSQL versions specified in
+the following table as these are the versions used for development and testing.
 
-GitLab version | Minimum PostgreSQL version
--|-
-10.0 | 9.6
-13.0 | 11
+| GitLab version | Minimum PostgreSQL version |
+| -------------- | -------------------------- |
+| 10.0           | 9.6                        |
+| 13.0           | 11                         |
 
-You must also ensure the `pg_trgm` and `btree_gist` extensions are [loaded into every
+You must also ensure the following extensions are [loaded into every
 GitLab database](postgresql_extensions.html).
 
+| Extension    | Minimum GitLab version |
+| ------------ | ---------------------- |
+| `pg_trgm`    | 8.6                    |
+| `btree_gist` | 13.1                   |
+
 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).
 

doc/update/upgrading_from_source.md

@@ -167,9 +167,12 @@ sudo make prefix=/usr/local install
 WARNING:
 From GitLab 13.0, you must use at least PostgreSQL 11.
 
-The latest version of GitLab might depend on a more recent PostgreSQL version than what you are currently running (see the [PostgreSQL requirements](../install/requirements.md#postgresql-requirements)).
+The latest version of GitLab might depend on a more recent PostgreSQL version
+than what you are currently running. You might also need to enable some
+extensions. See the [PostgreSQL requirements](../install/requirements.md#postgresql-requirements)
+for more information.
 
-In order to upgrade PostgreSQL, please refer to its [documentation](https://www.postgresql.org/docs/11/upgrading.html).
+In order to upgrade PostgreSQL, refer to its [documentation](https://www.postgresql.org/docs/11/upgrading.html).
 
 ### 8. Get latest code