Method: Sequel::Postgres::DatabaseMethods#convert_serial_to_identity

Defined in:

lib/sequel/adapters/shared/postgres.rb

#convert_serial_to_identity(table, opts = OPTS) ⇒ Object

Convert the first primary key column in the table from being a serial column to being an identity column. If the column is already an identity column, assume it was already converted and make no changes.

Only supported on PostgreSQL 10.2+, since on those versions Sequel will use identity columns instead of serial columns for auto incrementing primary keys. Only supported when running as a superuser, since regular users cannot modify system tables, and there is no way to keep an existing sequence when changing an existing column to be an identity column.

This method can raise an exception in at least the following cases where it may otherwise succeed (there may be additional cases not listed here):

• The serial column was added after table creation using PostgreSQL <7.3

• A regular index also exists on the column (such an index can probably be dropped as the primary key index should suffice)

Options:

:column

Specify the column to convert instead of using the first primary key column

:server

Run the SQL on the given server

Raises:

• (Error)

# File 'lib/sequel/adapters/shared/postgres.rb', line 363

def convert_serial_to_identity(table, opts=OPTS)
  raise Error, "convert_serial_to_identity is only supported on PostgreSQL 10.2+" unless server_version >= 100002

  server = opts[:server]
  server_hash = server ? {:server=>server} : OPTS
  ds = dataset
  ds = ds.server(server) if server

  raise Error, "convert_serial_to_identity requires superuser permissions" unless ds.get{current_setting('is_superuser')} == 'on'

  table_oid = regclass_oid(table)
  im = input_identifier_meth
  unless column = (opts[:column] || ((sch = schema(table).find{|_, sc| sc[:primary_key] && sc[:auto_increment]}) && sch[0]))
    raise Error, "could not determine column to convert from serial to identity automatically"
  end
  column = im.call(column)

  column_num = ds.from(:pg_attribute).
    where(:attrelid=>table_oid, :attname=>column).
    get(:attnum)

  pg_class = Sequel.cast('pg_class', :regclass)
  res = ds.from(:pg_depend).
    where(:refclassid=>pg_class, :refobjid=>table_oid, :refobjsubid=>column_num, :classid=>pg_class, :objsubid=>0, :deptype=>%w'a i').
    select_map([:objid, Sequel.as({:deptype=>'i'}, :v)])

  case res.length
  when 0
    raise Error, "unable to find related sequence when converting serial to identity"
  when 1
    seq_oid, already_identity = res.first
  else
    raise Error, "more than one linked sequence found when converting serial to identity"
  end

  return if already_identity

  transaction(server_hash) do
    run("ALTER TABLE #{quote_schema_table(table)} ALTER COLUMN #{quote_identifier(column)} DROP DEFAULT", server_hash)

    ds.from(:pg_depend).
      where(:classid=>pg_class, :objid=>seq_oid, :objsubid=>0, :deptype=>'a').
      update(:deptype=>'i')

    ds.from(:pg_attribute).
      where(:attrelid=>table_oid, :attname=>column).
      update(:attidentity=>'d')
  end

  remove_cached_schema(table)
  nil
end