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Update database requirements documentation with more MySQL limitations

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Michael Kozono 2018-09-18 10:56:26 +00:00 committed by Marcia Ramos
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doc/install/requirements.md
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@ -27,7 +27,7 @@ Please see the [installation from source guide](installation.md) and the [instal
### Non-Unix operating systems such as Windows
GitLab is developed for Unix operating systems.
GitLab is developed for Unix operating systems.
It does **not** run on Windows, and we have no plans to support it in the near future. For the latest development status view this [issue](https://gitlab.com/gitlab-org/gitlab-ce/issues/46567).
Please consider using a virtual machine to run GitLab.
@ -103,19 +103,21 @@ features of GitLab work with MySQL/MariaDB:
1. MySQL support for subgroups was [dropped with GitLab 9.3][post].
See [issue #30472][30472] for more information.
1. GitLab Geo does [not support MySQL](https://docs.gitlab.com/ee/gitlab-geo/database.html#mysql-replication).
1. [Zero downtime migrations][zero] do not work with MySQL
1. Geo **[STARTER ONLY]** does [not support MySQL](https://docs.gitlab.com/ee/gitlab-geo/database.html#mysql-replication). This means no supported Disaster Recovery solution if using MySQL.
1. [Zero downtime migrations][../update/README.md#upgrading-without-downtime] do not work with MySQL.
1. GitLab [optimizes the loading of dashboard events](https://gitlab.com/gitlab-org/gitlab-ce/issues/31806) using [PostgreSQL LATERAL JOINs](https://blog.heapanalytics.com/postgresqls-powerful-new-join-type-lateral/).
1. In general, SQL optimized for PostgreSQL may run much slower in MySQL due to
differences in query planners. For example, subqueries that work well in PostgreSQL
may not be [performant in MySQL](https://dev.mysql.com/doc/refman/5.7/en/optimizing-subqueries.html)
may not be [performant in MySQL](https://dev.mysql.com/doc/refman/5.7/en/optimizing-subqueries.html).
1. Binary column index length is limited to 20 bytes. This is accomplished with [a hack](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/config/initializers/mysql_set_length_for_binary_indexes.rb).
1. MySQL requires a variety of hacks to increase limits on various columns, [for example](https://gitlab.com/gitlab-org/gitlab-ce/issues/49583).
1. [The milestone filter runs slower queries on MySQL](https://gitlab.com/gitlab-org/gitlab-ce/issues/51173#note_99391731).
1. We expect this list to grow over time.
Existing users using GitLab with MySQL/MariaDB are advised to
[migrate to PostgreSQL](../update/mysql_to_postgresql.md) instead.
[30472]: https://gitlab.com/gitlab-org/gitlab-ce/issues/30472
[zero]: ../update/README.md#upgrading-without-downtime
[post]: https://about.gitlab.com/2017/06/22/gitlab-9-3-released/#dropping-support-for-subgroups-in-mysql
### PostgreSQL Requirements