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-rw-r--r--activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb8
1 files changed, 5 insertions, 3 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index f8c9e13392..b9a9c22198 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -965,11 +965,13 @@ module ActiveRecord
subsubselect = select.clone
subsubselect.projections = [key]
+ # Materialize subquery by adding distinct
+ # to work with MySQL 5.7.6 which sets optimizer_switch='derived_merge=on'
+ subsubselect.distinct unless select.limit || select.offset || select.orders.any?
+
subselect = Arel::SelectManager.new(select.engine)
subselect.project Arel.sql(key.name)
- # Materialized subquery by adding distinct
- # to work with MySQL 5.7.6 which sets optimizer_switch='derived_merge=on'
- subselect.from subsubselect.distinct.as('__active_record_temp')
+ subselect.from subsubselect.as('__active_record_temp')
end
def mariadb?