1 files changed, 30 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
index 3ad1911a28..469ef3f5a0 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     # PostgreSQL-specific extensions to column definitions in a table.
@@ -5,11 +7,38 @@ module ActiveRecord
       delegate :array, :oid, :fmod, to: :sql_type_metadata
       alias :array? :array
 
+      def initialize(*, max_identifier_length: 63, **)
+        super
+        @max_identifier_length = max_identifier_length
+      end
+
       def serial?
         return unless default_function
 
-        %r{\Anextval\('"?#{table_name}_#{name}_seq"?'::regclass\)\z} === default_function
+        if %r{\Anextval\('"?(?<sequence_name>.+_(?<suffix>seq\d*))"?'::regclass\)\z} =~ default_function
+          sequence_name_from_parts(table_name, name, suffix) == sequence_name
+        end
       end
+
+      protected
+        attr_reader :max_identifier_length
+
+      private
+        def sequence_name_from_parts(table_name, column_name, suffix)
+          over_length = [table_name, column_name, suffix].map(&:length).sum + 2 - max_identifier_length
+
+          if over_length > 0
+            column_name_length = [(max_identifier_length - suffix.length - 2) / 2, column_name.length].min
+            over_length -= column_name.length - column_name_length
+            column_name = column_name[0, column_name_length - [over_length, 0].min]
+          end
+
+          if over_length > 0
+            table_name = table_name[0, table_name.length - over_length]
+          end
+
+          "#{table_name}_#{column_name}_#{suffix}"
+        end
     end
   end
 end