Allow bigint with default nil for avoiding auto increment primary key

Such as #10404, #18206.

2 files changed, 6 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
index 29e8c73d46..ca7dfda80d 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
@@ -3,7 +3,7 @@ module ActiveRecord
     module MySQL
       module ColumnMethods
         def primary_key(name, type = :primary_key, **options)
-          options[:auto_increment] = true if type == :bigint
+          options[:auto_increment] = true if type == :bigint && !options.key?(:default)
           super
         end
 
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
index 3c48d0554e..9dee3172f4 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
@@ -4,8 +4,11 @@ module ActiveRecord
       module ColumnDumper
         def column_spec_for_primary_key(column)
           spec = {}
-          if column.auto_increment?
-            spec[:id] = ':bigint' if column.bigint?
+          if column.bigint?
+            spec[:id] = ':bigint'
+            spec[:default] = schema_default(column) || 'nil' unless column.auto_increment?
+            spec[:unsigned] = 'true' if column.unsigned?
+          elsif column.auto_increment?
             spec[:unsigned] = 'true' if column.unsigned?
             return if spec.empty?
           else