Support VIRTUAL generated columns on PostgreSQL 18+ using :virtual option

PostgreSQL 18+ made the default VIRTUAL if not specified. This doesn't
break backwards compatibility, as STORED was required previously.

Unfortunately, making VIRTUAL the default in Sequel would break
backwards compatibility. So in Sequel, the default will remain
to have STORED as the default, and require the :virtual option to
use VIRTUAL.

Author: jeremyevans

CHANGELOG

@@ -1,3 +1,7 @@
+=== master
+
+* Support VIRTUAL generated columns on PostgreSQL 18+ using :virtual option (jeremyevans)
+
 === 5.95.1 (2025-08-05)
 
 * Fix regression in 5.95.0 where :deferred would be ignored for unique and primary key constraints on PostgreSQL (jeremyevans) (#2321)

lib/sequel/adapters/shared/postgres.rb

@@ -1291,7 +1291,7 @@ def column_definition_default_sql(sql, column)
             sql << (identity == :always ? "ALWAYS" : "BY DEFAULT")
             sql << " AS IDENTITY"
           elsif (generated = column[:generated_always_as])
-            sql << " GENERATED ALWAYS AS (#{literal(generated)}) STORED"
+            sql << " GENERATED ALWAYS AS (#{literal(generated)}) #{column[:virtual] ? 'VIRTUAL' : 'STORED'}"
           end
         end
       end

lib/sequel/database/schema_generator.rb

@@ -156,6 +156,9 @@ def check(*args, &block)
       # PostgreSQL specific options:
       #
       # :identity :: Create an identity column.
+      # :virtual :: When using :generated_always_as, create a VIRTUAL column instead of a STORED
+      #             column (PostgreSQL 18+). VIRTUAL is the default if not specified on
+      #             PostgreSQL 18+, but for backwards compatibility, Sequel's default is STORED.
       #
       # MySQL specific options:
       #

spec/adapters/postgres_spec.rb

@@ -740,6 +740,12 @@ def c.exec_prepared(*); super; nil end
     @db[:tmp_dolls].select_order_map([:a, :b, :c]).must_equal [[100, 10, 211]]
   end if DB.server_version >= 120000
 
+  it "should support creating generated virtual columns" do
+    @db.create_table(:tmp_dolls){Integer :a; Integer :b; Integer :c, :generated_always_as=>Sequel[:a] * 2 + :b + 1, :virtual=>true}
+    @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 >= 180000
+
   it "should include :generated entry in schema for whether the column is generated" do
     @db.create_table(:tmp_dolls){Integer :a; Integer :b; Integer :c, :generated_always_as=>Sequel[:a] * 2 + :b + 1}
     @db.schema(:tmp_dolls).map{|_,v| v[:generated]}.must_equal [false, false, true]

spec/core/mock_adapter_spec.rb

@@ -886,6 +886,16 @@ def @db.regclass_oid(x) 1234 end
     ]
   end
 
+  it "should default generated columns to STORED" do
+    @db.create_table(:t){Integer :c, :generated_always_as=>Sequel[:t] + 1}
+    @db.sqls.must_equal ['CREATE TABLE "t" ("c" integer GENERATED ALWAYS AS (("t" + 1)) STORED)']
+  end
+
+  it "should create VIRTUAL generated columns if given :virtual option" do
+    @db.create_table(:t){Integer :c, :generated_always_as=>Sequel[:t] + 1, :virtual=>true}
+    @db.sqls.must_equal ['CREATE TABLE "t" ("c" integer GENERATED ALWAYS AS (("t" + 1)) VIRTUAL)']
+  end
+
   it "should not support converting serial columns to identity on PostgreSQL <10.2" do
     def @db.server_version; 100000; end
     proc{@db.convert_serial_to_identity(:table)}.must_raise Sequel::Error