Bring back ability to insert zero value on primary key for fixtures (#31795)

Since #29504, mysql2 adapter lost ability to insert zero value on
primary key due to enforce `NO_AUTO_VALUE_ON_ZERO` disabled.
That is for using `DEFAULT` on auto increment column, but we can use
`NULL` instead in that case.

1 files changed, 4 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
index d663b59444..08f3e15a4b 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
@@ -414,6 +414,9 @@ module ActiveRecord
       alias join_to_delete join_to_update
 
       private
+        def default_insert_value(column)
+          Arel.sql("DEFAULT")
+        end
 
         def build_fixture_sql(fixtures, table_name)
           columns = schema_cache.columns_hash(table_name)
@@ -432,7 +435,7 @@ module ActiveRecord
                 bind = Relation::QueryAttribute.new(name, fixture[name], type)
                 with_yaml_fallback(bind.value_for_database)
               else
-                Arel.sql("DEFAULT")
+                default_insert_value(column)
               end
             end
           end