Commit a488fc0a authored by Toon Claes's avatar Toon Claes

Add workaround for UPDATE with subquery when using MySQL

When trying to run an UPDATE, this query is ran:

```sql
UPDATE `todos`
INNER JOIN `projects` ON `projects`.`id` = `todos`.`project_id`
SET `todos`.`state` = 'done'
WHERE `todos`.`user_id` = 4
  AND (`todos`.`state` IN ('pending'))
  AND (EXISTS
         (SELECT 1
          FROM `project_authorizations`
          WHERE `project_authorizations`.`user_id` = 4
            AND (project_authorizations.project_id = projects.id))
       OR projects.visibility_level IN (10,
                                        20))
  AND `projects`.`id` IN
    (SELECT `todos`.`project_id`
     FROM `todos`
     WHERE `todos`.`user_id` = 4
       AND (`todos`.`state` IN ('pending')))
  AND (`todos`.`state` != 'done')
```

But MySQL does not like the subquery used to filter on
`projects.id IN (SELECT ...`

Because the subquery queries from the same table:

> Error: You can’t specify target table ‘todos’ for update in FROM clause

So as workaround, wrap it in another subquery, where the original
subquery is aliased using the `AS` statement.

Mostly inspired by https://stackoverflow.com/a/43610081/89376
parent a723cba5
...@@ -95,9 +95,18 @@ class TodosFinder ...@@ -95,9 +95,18 @@ class TodosFinder
@project @project
end end
def project_ids(items)
ids = items.except(:order).select(:project_id)
if Gitlab::Database.mysql?
# To make UPDATE work on MySQL, wrap it in a SELECT with an alias
ids = Todo.except(:order).select('*').from("(#{ids.to_sql}) AS t")
end
ids
end
def projects(items) def projects(items)
item_project_ids = items.reorder(nil).select(:project_id) ProjectsFinder.new(current_user: current_user, project_ids_relation: project_ids(items)).execute
ProjectsFinder.new(current_user: current_user, project_ids_relation: item_project_ids).execute
end end
def type? def type?
......
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