Commit 35b93f9d authored by Kamil Trzciński's avatar Kamil Trzciński

Add notice about offline migrations

parent a9f02300
...@@ -8,6 +8,8 @@ In addition, having to take a server offline for a an upgrade small or big is ...@@ -8,6 +8,8 @@ In addition, having to take a server offline for a an upgrade small or big is
a big burden for most organizations. For this reason it is important that your a big burden for most organizations. For this reason it is important that your
migrations are written carefully, can be applied online and adhere to the style guide below. migrations are written carefully, can be applied online and adhere to the style guide below.
It's advised to have offline migrations only in major GitLab releases.
When writing your migrations, also consider that databases might have stale data When writing your migrations, also consider that databases might have stale data
or inconsistencies and guard for that. Try to make as little assumptions as possible or inconsistencies and guard for that. Try to make as little assumptions as possible
about the state of the database. about the state of the database.
...@@ -33,6 +35,8 @@ It is always preferable to have a migration run online. If you expect the migrat ...@@ -33,6 +35,8 @@ It is always preferable to have a migration run online. If you expect the migrat
to take particularly long (for instance, if it loops through all notes), to take particularly long (for instance, if it loops through all notes),
this is valuable information to add. this is valuable information to add.
If you don't provide the information it means that a migration is safe to run online.
### Reversibility ### Reversibility
Your migration should be reversible. This is very important, as it should Your migration should be reversible. This is very important, as it should
...@@ -85,4 +89,4 @@ select_all("SELECT name, COUNT(id) as cnt FROM tags GROUP BY name HAVING COUNT(i ...@@ -85,4 +89,4 @@ select_all("SELECT name, COUNT(id) as cnt FROM tags GROUP BY name HAVING COUNT(i
execute("UPDATE taggings SET tag_id = #{origin_tag_id} WHERE tag_id IN(#{duplicate_ids.join(",")})") execute("UPDATE taggings SET tag_id = #{origin_tag_id} WHERE tag_id IN(#{duplicate_ids.join(",")})")
execute("DELETE FROM tags WHERE id IN(#{duplicate_ids.join(",")})") execute("DELETE FROM tags WHERE id IN(#{duplicate_ids.join(",")})")
end end
``` ```
\ No newline at end of file
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