Deprecate config.active_record.warn_on_records_fetched_greater_than (rails#51007)

* Deprecate config.active_record.warn_on_records_fetched_greater_than

* Review changes

Co-authored-by: Rafael Mendonça França <[email protected]>

---------

Co-authored-by: Jason Nochlin <[email protected]>
Co-authored-by: Rafael Mendonça França <[email protected]>

Author: hundredwatt

activerecord/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Deprecate `config.active_record.warn_on_records_fetched_greater_than` now that `sql.active_record`
+    notification includes `:row_count` field.
+
+    *Jason Nochlin*
+
 *   Fix an issue where `ActiveRecord::Encryption` configurations are not ready before the loading
     of Active Record models, when an application is eager loaded. As a result, encrypted attributes
     could be misconfigured in some cases.

activerecord/lib/active_record/railtie.rb

@@ -223,6 +223,12 @@ class Railtie < Rails::Railtie # :nodoc:
 
     initializer "active_record.warn_on_records_fetched_greater_than" do
       if config.active_record.warn_on_records_fetched_greater_than
+        ActiveRecord.deprecator.warn <<~MSG.squish
+          `config.active_record.warn_on_records_fetched_greater_than` is deprecated and will be
+          removed in Rails 7.3.
+          Please subscribe to `sql.active_record` notifications and access the row count field to
+          detect large result set sizes.
+        MSG
         ActiveSupport.on_load(:active_record) do
           require "active_record/relation/record_fetch_warning"
         end

activerecord/lib/active_record/relation/record_fetch_warning.rb

@@ -3,6 +3,9 @@
 module ActiveRecord
   class Relation
     module RecordFetchWarning
+      # Deprecated: subscribe to sql.active_record notifications and
+      # access the row count field to detect large result set sizes.
+      #
       # When this module is prepended to ActiveRecord::Relation and
       # +config.active_record.warn_on_records_fetched_greater_than+ is
       # set to an integer, if the number of records a query returns is