Support :generated_always_as column option on PostgreSQL 12+

This option was already supported on recent versions of MariaDB
and MySQL.  PostgreSQL 12+ doesn't support virtual columns, so
currently the :generated_type option is not supported.

CHANGELOG

@@ -1,3 +1,7 @@
+=== master
+
+* Support :generated_always_as column option on PostgreSQL 12+ (jeremyevans)
+
 === 5.23.0 (2019-08-01)
 
 * Work around a bug on jdbc-sqlite3 3.27.2.1 when parsing schema for tables with columns with default values (jeremyevans)

lib/sequel/adapters/shared/postgres.rb

@@ -836,10 +836,14 @@ def column_definition_collate_sql(sql, column)
  # default value is given.
  def column_definition_default_sql(sql, column)
  super
- if !column[:serial] && !['serial', 'bigserial'].include?(column[:type].to_s) && !column[:default] && (identity = column[:identity])
- sql << " GENERATED "
- sql << (identity == :always ? "ALWAYS" : "BY DEFAULT")
- sql << " AS IDENTITY"
+ if !column[:serial] && !['serial', 'bigserial'].include?(column[:type].to_s) && !column[:default]
+ if (identity = column[:identity])
+ sql << " GENERATED "
+ sql << (identity == :always ? "ALWAYS" : "BY DEFAULT")
+ sql << " AS IDENTITY"
+ elsif (generated = column[:generated_always_as])
+ sql << " GENERATED ALWAYS AS (#{literal(generated)}) STORED"
+ end
  end
  end
 

lib/sequel/database/schema_generator.rb

@@ -110,6 +110,9 @@ def check(*args, &block)
  # yet exist on referenced table (but will exist before the transaction commits).
  # Basically it adds DEFERRABLE INITIALLY DEFERRED on key creation.
  # If you use :immediate as the value, uses DEFERRABLE INITIALLY IMMEDIATE.
+ # :generated_always_as :: Specify a GENERATED ALWAYS AS column expression,
+ # if generated columns are supported (PostgreSQL 12+, MariaDB 5.2.0+,
+ # and MySQL 5.7.6+).
  # :index :: Create an index on this column. If given a hash, use the hash as the
  # options for the index.
  # :key :: For foreign key columns, the column in the associated table
@@ -132,9 +135,11 @@ def check(*args, &block)
  # creating a unique index on the column.
  # :unique_constraint_name :: The name to give the unique key constraint
  #
+ # PostgreSQL specific options:
+ #
+ # :identity :: Create an identity column.
+ #
  # MySQL specific options:
- # :generated_always_as :: Specify a GENERATED ALWAYS AS column expression,
- # if generated columns are supported.
  # :generated_type :: Set the type of column when using :generated_always_as,
  # should be :virtual or :stored to force a type.
  def column(name, type, opts = OPTS)

spec/adapters/postgres_spec.rb

@@ -227,6 +227,12 @@
  @db.convert_serial_to_identity(:tmp_dolls, :column=>:id)
  end if DB.server_version >= 100002 && DB.get{current_setting('is_superuser')} == 'on'
 
+ it "should support creating generated columns" do
+ @db.create_table(:tmp_dolls){Integer :a; Integer :b; Integer :c, :generated_always_as=>Sequel[:a] * 2 + :b + 1}
+ @db[:tmp_dolls].insert(:a=>100, :b=>10)
+ @db[:tmp_dolls].select_order_map([:a, :b, :c]).must_equal [[100, 10, 211]]
+ end if DB.server_version >= 120000
+
  it "should support pg_loose_count extension" do
  @db.extension :pg_loose_count
  @db.create_table(:tmp_dolls){text :name}