Skip query cache for in_batches and friends

The `find_each`, `find_in_batches` and `in_batches` APIs usually operate
on large numbers of records, where it's preferable not to load them all
into memory at once.

If the query cache is enabled, it will hold onto the query results until
the end of the execution context (request/job), which means the memory
used is still proportional to the total number of records. These queries
are typically not repeated, so the query cache isn't desirable here.

1 files changed, 3 insertions, 3 deletions

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] }