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doc/development/database/index.md

@@ -69,3 +69,4 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 ## Miscellaneous
 
 - [Maintenance operations](maintenance_operations.md)
+- [Update multiple database objects](setting_multiple_values.md)

doc/development/database/setting_multiple_values.md

@@ -4,24 +4,22 @@ group: Database
 info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
 ---
 
-# Setting Multiple Values
+# Update multiple database objects
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/32921) in GitLab 13.5.
 
-There's often a need to update multiple objects with new values for one
-or more columns. One method of doing this is using `Relation#update_all`:
+You can update multiple database objects with new values for one or more columns.
+One method is to use `Relation#update_all`:
 
 ```ruby
 user.issues.open.update_all(due_date: 7.days.from_now) # (1)
 user.issues.update_all('relative_position = relative_position + 1') # (2)
 ```
 
-But what do you do if you cannot express the update as either a static value (1)
-or as a calculation (2)?
-
-Thankfully we can use `UPDATE FROM` to express the need to update multiple rows
-with distinct values in a single query. One can either use a temporary table, or
-a Common Table Expression (CTE), and then use that as the source of the updates:
+If you cannot express the update as either a static value (1) or as a calculation (2),
+use `UPDATE FROM` to express the need to update multiple rows with distinct values
+in a single query. Create a temporary table, or a Common Table Expression (CTE),
+and use it as the source of the updates:
 
 ```sql
 with updates(obj_id, new_title, new_weight) as (
@@ -34,23 +32,22 @@ update issues
   where id = obj_id
 ```
 
-The bad news: there is no way to express this in ActiveRecord or even dropping
-down to ARel. The `UpdateManager` does not support `update from`, so this
-is not expressible.
-
-The good news: we supply an abstraction to help you generate these kinds of
-updates, called `Gitlab::Database::BulkUpdate`. This constructs queries such as the
-above, and uses binding parameters to avoid SQL injection.
+You can't express this in ActiveRecord, or by dropping down to [Arel](https://api.rubyonrails.org/v6.1.0/classes/Arel.html),
+because the `UpdateManager` does not support `update from`. However, we supply
+an abstraction to help you generate these kinds of updates: `Gitlab::Database::BulkUpdate`.
+This abstraction constructs queries like the previous example, and uses
+binding parameters to avoid SQL injection.
 
 ## Usage
 
-To use this, we need:
+To use `Gitlab::Database::BulkUpdate`, we need:
 
-- the list of columns to update
-- a mapping from object/ID to the new values to set for that object
-- a way to determine the table for each object
+- The list of columns to update.
+- A mapping from the object (or ID) to the new values to set for that object.
+- A way to determine the table for each object.
 
-For example, we can express the query above as:
+For example, we can express the example query in a way that determines the
+table by calling `object.class.table_name`:
 
 ```ruby
 issue_a = Issue.find(..)
@@ -63,10 +60,7 @@ issue_b = Issue.find(..)
 })
 ```
 
-Here the table can be determined automatically, from calling
-`object.class.table_name`, so we don't need to provide anything.
-
-We can even pass heterogeneous sets of objects, if the updates all make sense
+You can even pass heterogeneous sets of objects, if the updates all make sense
 for them:
 
 ```ruby
@@ -82,8 +76,8 @@ merge_request = MergeRequest.find(..)
 })
 ```
 
-If your objects do not return the correct model class (perhaps because they are
-part of a union), then we need to specify this explicitly in a block:
+If your objects do not return the correct model class, such as if they are part
+of a union, then specify the model class explicitly in a block:
 
 ```ruby
 bazzes = params
@@ -103,7 +97,10 @@ end
 
 ## Caveats
 
-Note that this is a **very low level** tool, and operates on the raw column
-values. Enumerations and state fields must be translated into their underlying
-representations, for example, and nested associations are not supported. No
-validations or hooks are called.
+This tool is **very low level**, and operates directly on the raw column
+values. You should consider these issues if you implement it:
+
+- Enumerations and state fields must be translated into their underlying
+  representations.
+- Nested associations are not supported.
+- No validations or hooks are called.