Add dirties option to uncached (rails#51204)

This adds a `dirties` option to `ActiveRecord::Base.uncached` and
`ActiveRecord::ConnectionAdapters::ConnectionPool#uncached`.

Setting `dirties` to `false`, means database writes to the connection
pool will not mark any query caches as dirty.

The option defaults to `true` which retains the existing behaviour and
clears query caches on all connection pools used by the current thread.

Co-authored-by: Jeremy Daer <[email protected]>

Author: djmb

activerecord/CHANGELOG.md

@@ -1,3 +1,15 @@
+*   Add dirties option to uncached
+
+    This adds a `dirties` option to `ActiveRecord::Base.uncached` and
+    `ActiveRecord::ConnectionAdapters::ConnectionPool#uncached`.
+
+    When set to `true` (the default), writes will clear all query caches belonging to the current thread.
+    When set to `false`, writes to the affected connection pool will not clear any query cache.
+
+    This is needed by Solid Cache so that cache writes do not clear query caches.
+
+    *Donal McBreen*
+
 *   Deprecate `ActiveRecord::Base.connection` in favor of `.lease_connection`
 
     The method has been renamed as `lease_connection` to better reflect that the returned

activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb

@@ -41,9 +41,14 @@ def connection_class; end
       def checkin(_); end
       def remove(_); end
       def async_executor; end
+
       def db_config
         NULL_CONFIG
       end
+
+      def dirties_query_cache
+        true
+      end
     end
 
     # = Active Record Connection Pool

activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb

@@ -20,7 +20,9 @@ def dirties_query_cache(base, *method_names)
           method_names.each do |method_name|
             base.class_eval <<-end_code, __FILE__, __LINE__ + 1
               def #{method_name}(...)
-                ActiveRecord::Base.clear_query_caches_for_current_thread
+                if pool.dirties_query_cache
+                  ActiveRecord::Base.clear_query_caches_for_current_thread
+                end
                 super
               end
             end_code
@@ -29,13 +31,15 @@ def #{method_name}(...)
       end
 
       class Store # :nodoc:
-        attr_accessor :enabled
+        attr_accessor :enabled, :dirties
         alias_method :enabled?, :enabled
+        alias_method :dirties?, :dirties
 
         def initialize(max_size)
           @map = {}
           @max_size = max_size
           @enabled = false
+          @dirties = true
         end
 
         def size
@@ -96,38 +100,42 @@ def lease_connection
         end
 
         # Disable the query cache within the block.
-        def disable_query_cache
+        def disable_query_cache(dirties: true)
           cache = query_cache
-          old, cache.enabled = cache.enabled, false
+          old_enabled, cache.enabled, old_dirties, cache.dirties = cache.enabled, false, cache.dirties, dirties
           begin
             yield
           ensure
-            cache.enabled = old
+            cache.enabled, cache.dirties = old_enabled, old_dirties
           end
         end
 
         def enable_query_cache
           cache = query_cache
-          old, cache.enabled = cache.enabled, true
+          old_enabled, cache.enabled, old_dirties, cache.dirties = cache.enabled, true, cache.dirties, true
           begin
             yield
           ensure
-            cache.enabled = old
+            cache.enabled, cache.dirties = old_enabled, old_dirties
           end
         end
 
         def enable_query_cache!
-          query_cache.enabled = true
+          query_cache.enabled, query_cache.dirties = true, true
         end
 
         def disable_query_cache!
-          query_cache.enabled = false
+          query_cache.enabled, query_cache.dirties = false, true
         end
 
         def query_cache_enabled
           query_cache.enabled
         end
 
+        def dirties_query_cache
+          query_cache.dirties
+        end
+
         def clear_query_cache
           if @pinned_connection
             # With transactional fixtures, and especially systems test
@@ -175,8 +183,11 @@ def enable_query_cache!
       end
 
       # Disable the query cache within the block.
-      def uncached(&)
-        pool.disable_query_cache(&)
+      #
+      # Set <tt>dirties: false</tt> to prevent query caches on all connections from being cleared by write operations.
+      # (By default, write operations dirty all connections' query caches in case they are replicas whose cache would now be outdated.)
+      def uncached(dirties: true, &)
+        pool.disable_query_cache(dirties: dirties, &)
       end
 
       def disable_query_cache!

activerecord/lib/active_record/query_cache.rb

@@ -22,9 +22,12 @@ def cache(&block)
 
       # Disable the query cache within the block if Active Record is configured.
       # If it's not, it will execute the given block.
-      def uncached(&block)
+      #
+      # Set <tt>dirties: false</tt> to prevent query caches on all connections from being cleared by write operations.
+      # (By default, write operations dirty all connections' query caches in case they are replicas whose cache would now be outdated.)
+      def uncached(dirties: true, &block)
         if connected? || !configurations.empty?
-          connection_pool.disable_query_cache(&block)
+          connection_pool.disable_query_cache(dirties: dirties, &block)
         else
           yield
         end

activerecord/test/cases/query_cache_test.rb

@@ -706,6 +706,57 @@ def test_clear_query_cache_is_called_on_all_connections
     end
   end
 
+  def test_query_cache_uncached_dirties
+    mw = middleware { |env|
+      Post.first
+      assert_no_changes -> { ActiveRecord::Base.connection.query_cache.size } do
+        Post.uncached(dirties: false) { Post.create!(title: "a new post", body: "and a body") }
+      end
+
+      assert_changes -> { ActiveRecord::Base.connection.query_cache.size }, from: 1, to: 0 do
+        Post.uncached(dirties: true) { Post.create!(title: "a new post", body: "and a body") }
+      end
+    }
+    mw.call({})
+  end
+
+  def test_query_cache_connection_uncached_dirties
+    mw = middleware { |env|
+      Post.first
+      assert_no_changes -> { ActiveRecord::Base.connection.query_cache.size } do
+        Post.connection.uncached(dirties: false) { Post.create!(title: "a new post", body: "and a body") }
+      end
+
+      assert_changes -> { ActiveRecord::Base.connection.query_cache.size }, from: 1, to: 0 do
+        Post.connection.uncached(dirties: true) { Post.create!(title: "a new post", body: "and a body") }
+      end
+    }
+    mw.call({})
+  end
+
+  def test_query_cache_uncached_dirties_disabled_with_nested_cache
+    mw = middleware { |env|
+      Post.first
+      assert_changes -> { ActiveRecord::Base.connection.query_cache.size }, from: 1, to: 0 do
+        Post.uncached(dirties: false) do
+          Post.cache do
+            Post.create!(title: "a new post", body: "and a body")
+          end
+        end
+      end
+
+      Post.first
+      assert_changes -> { ActiveRecord::Base.connection.query_cache.size }, from: 1, to: 0 do
+        Post.connection.uncached(dirties: false) do
+          Post.connection.cache do
+            Post.create!(title: "a new post", body: "and a body")
+          end
+        end
+      end
+    }
+    mw.call({})
+  end
+
   private
     def with_temporary_connection_pool(&block)
       pool_config = ActiveRecord::Base.lease_connection.pool.pool_config