Merge pull request rails#49504 from fatkodima/fix-pg-retrieving-ident…

…ity-columns

Fix auto populating `IDENTITY` columns for PostgreSQL

activerecord/lib/active_record/connection_adapters/postgresql/column.rb

@@ -6,16 +6,24 @@ module PostgreSQL
       class Column < ConnectionAdapters::Column # :nodoc:
         delegate :oid, :fmod, to: :sql_type_metadata
 
-        def initialize(*, serial: nil, generated: nil, **)
+        def initialize(*, serial: nil, identity: nil, generated: nil, **)
           super
           @serial = serial
+          @identity = identity
           @generated = generated
         end
 
+        def identity?
+          @identity
+        end
+
         def serial?
           @serial
         end
-        alias_method :auto_incremented_by_db?, :serial?
+
+        def auto_incremented_by_db?
+          serial? || identity?
+        end
 
         def virtual?
           # We assume every generated column is virtual, no matter the concrete type
@@ -41,26 +49,30 @@ def sql_type
 
         def init_with(coder)
           @serial = coder["serial"]
+          @identity = coder["identity"]
           @generated = coder["generated"]
           super
         end
 
         def encode_with(coder)
           coder["serial"] = @serial
+          coder["identity"] = @identity
           coder["generated"] = @generated
           super
         end
 
         def ==(other)
           other.is_a?(Column) &&
             super &&
+            identity? == other.identity? &&
             serial? == other.serial?
         end
         alias :eql? :==
 
         def hash
           Column.hash ^
             super.hash ^
+            identity?.hash ^
             serial?.hash
         end
       end

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

@@ -908,7 +908,7 @@ def create_alter_table(name)
           end
 
           def new_column_from_field(table_name, field, _definitions)
-            column_name, type, default, notnull, oid, fmod, collation, comment, attgenerated = field
+            column_name, type, default, notnull, oid, fmod, collation, comment, identity, attgenerated = field
             type_metadata = fetch_type_metadata(column_name, type, oid.to_i, fmod.to_i)
             default_value = extract_value_from_default(default)
 
@@ -931,6 +931,7 @@ def new_column_from_field(table_name, field, _definitions)
               collation: collation,
               comment: comment.presence,
               serial: serial,
+              identity: identity.presence,
               generated: attgenerated
             )
           end

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -1084,6 +1084,7 @@ def column_definitions(table_name)
               SELECT a.attname, format_type(a.atttypid, a.atttypmod),
                      pg_get_expr(d.adbin, d.adrelid), a.attnotnull, a.atttypid, a.atttypmod,
                      c.collname, col_description(a.attrelid, a.attnum) AS comment,
+                     a.attidentity AS identity,
                      #{supports_virtual_columns? ? 'attgenerated' : quote('')} as attgenerated
                 FROM pg_attribute a
                 LEFT JOIN pg_attrdef d ON a.attrelid = d.adrelid AND a.attnum = d.adnum

activerecord/test/cases/persistence_test.rb

@@ -54,6 +54,15 @@ def test_fills_auto_populated_columns_on_creation
     assert_not_nil record_with_defaults.modified_time
     assert_not_nil record_with_defaults.modified_time_without_precision
     assert_not_nil record_with_defaults.modified_time_function
+
+    if current_adapter?(:PostgreSQLAdapter)
+      klass = Class.new(ActiveRecord::Base) do
+        self.table_name = "postgresql_identity_table"
+      end
+
+      record = klass.create!
+      assert_not_nil record.id
+    end
   end if current_adapter?(:PostgreSQLAdapter) || current_adapter?(:SQLite3Adapter)
 
   def test_update_many

activerecord/test/schema/postgresql_specific_schema.rb

@@ -46,6 +46,13 @@
 "
   end
 
+  drop_table "postgresql_identity_table", if_exists: true
+  execute <<~SQL
+    create table postgresql_identity_table (
+      id INT PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY
+    )
+  SQL
+
   create_table :postgresql_times, force: true do |t|
     t.interval :time_interval
     t.interval :scaled_time_interval, precision: 6