Merge pull request #28867 from eugeneius/skip_query_cache_in_batches

Skip query cache for in_batches and friends

5 files changed, 37 insertions, 19 deletions

diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 52f5d5f3e3..76cf47a3ed 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -6,7 +6,7 @@ module ActiveRecord
                             :extending, :unscope]
 
     SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :reordering,
-                            :reverse_order, :distinct, :create_with]
+                            :reverse_order, :distinct, :create_with, :skip_query_cache]
     CLAUSE_METHODS = [:where, :having, :from]
     INVALID_METHODS_FOR_DELETE_ALL = [:limit, :distinct, :offset, :group, :having]
 
@@ -657,20 +657,32 @@ module ActiveRecord
       end
 
       def exec_queries(&block)
-        @records = eager_loading? ? find_with_associations.freeze : @klass.find_by_sql(arel, bound_attributes, &block).freeze
-
-        preload = preload_values
-        preload += includes_values unless eager_loading?
-        preloader = nil
-        preload.each do |associations|
-          preloader ||= build_preloader
-          preloader.preload @records, associations
-        end
+        skip_query_cache_if_necessary do
+          @records = eager_loading? ? find_with_associations.freeze : @klass.find_by_sql(arel, bound_attributes, &block).freeze
+
+          preload = preload_values
+          preload += includes_values unless eager_loading?
+          preloader = nil
+          preload.each do |associations|
+            preloader ||= build_preloader
+            preloader.preload @records, associations
+          end
 
-        @records.each(&:readonly!) if readonly_value
+          @records.each(&:readonly!) if readonly_value
 
-        @loaded = true
-        @records
+          @loaded = true
+          @records
+        end
+      end
+
+      def skip_query_cache_if_necessary
+        if skip_query_cache_value
+          uncached do
+            yield
+          end
+        else
+          yield
+        end
       end
 
       def build_preloader
diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
index ee1f25ec84..c7e4f8a88a 100644
--- a/activerecord/lib/active_record/relation/batches.rb
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -209,6 +209,7 @@ module ActiveRecord
 
       relation = relation.reorder(batch_order).limit(batch_limit)
       relation = apply_limits(relation, start, finish)
+      relation.skip_query_cache! # Retaining the results in the query cache would undermine the point of batching
       batch_relation = relation
 
       loop do
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 8a54f8f2c3..aaba6c71f2 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -184,7 +184,7 @@ module ActiveRecord
         relation.select_values = column_names.map { |cn|
           @klass.has_attribute?(cn) || @klass.attribute_alias?(cn) ? arel_attribute(cn) : cn
         }
-        result = klass.connection.select_all(relation.arel, nil, bound_attributes)
+        result = skip_query_cache_if_necessary { klass.connection.select_all(relation.arel, nil, bound_attributes) }
         result.cast_values(klass.attribute_types)
       end
     end
@@ -260,7 +260,7 @@ module ActiveRecord
           query_builder = relation.arel
         end
 
-        result = @klass.connection.select_all(query_builder, nil, bound_attributes)
+        result = skip_query_cache_if_necessary { @klass.connection.select_all(query_builder, nil, bound_attributes) }
         row    = result.first
         value  = row && row.values.first
         type   = result.column_types.fetch(column_alias) do
@@ -311,7 +311,7 @@ module ActiveRecord
         relation.group_values  = group_fields
         relation.select_values = select_values
 
-        calculated_data = @klass.connection.select_all(relation.arel, nil, relation.bound_attributes)
+        calculated_data = skip_query_cache_if_necessary { @klass.connection.select_all(relation.arel, nil, relation.bound_attributes) }
 
         if association
           key_ids     = calculated_data.collect { |row| row[group_aliases.first] }
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index eee0f36f63..ac0b4f597e 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -315,7 +315,7 @@ module ActiveRecord
 
       relation = construct_relation_for_exists(relation, conditions)
 
-      connection.select_value(relation.arel, "#{name} Exists", relation.bound_attributes) ? true : false
+      skip_query_cache_if_necessary { connection.select_value(relation.arel, "#{name} Exists", relation.bound_attributes) } ? true : false
     rescue ::RangeError
       false
     end
@@ -376,7 +376,7 @@ module ActiveRecord
           if ActiveRecord::NullRelation === relation
             []
           else
-            rows = connection.select_all(relation.arel, "SQL", relation.bound_attributes)
+            rows = skip_query_cache_if_necessary { connection.select_all(relation.arel, "SQL", relation.bound_attributes) }
             join_dependency.instantiate(rows, aliases)
           end
         end
@@ -424,7 +424,7 @@ module ActiveRecord
 
         relation = relation.except(:select).select(values).distinct!
 
-        id_rows = @klass.connection.select_all(relation.arel, "SQL", relation.bound_attributes)
+        id_rows = skip_query_cache_if_necessary { @klass.connection.select_all(relation.arel, "SQL", relation.bound_attributes) }
         id_rows.map { |row| row[primary_key] }
       end
 
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index 9da8f96337..79495ead91 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -913,6 +913,11 @@ module ActiveRecord
       self
     end
 
+    def skip_query_cache! # :nodoc:
+      self.skip_query_cache_value = true
+      self
+    end
+
     # Returns the Arel object associated with the relation.
     def arel # :nodoc:
       @arel ||= build_arel