What is the equivalent of timestamp/rowversion (SQL Server) with PostgreSQL

See the system columns section in PostgreSQL documentation. In particular, xmin might be what you're looking for.

But be careful using any system columns. They are by definition implementation specific and the details of some of them might change with future versions.

You can create it manually:

1. Create sequence
2. Create trigger for insert and update for each table that contains rowversion column
3. Set rowversion column from sequence

The key thing being missed is that rowversion type changed each time there is an update to the row, even if the net result is that, the row is not changed.

CREATE TABLE MyTest (myKey int PRIMARY KEY  
    ,myValue int, RV rowversion);  
GO   
INSERT INTO MyTest (myKey, myValue) VALUES (1, 0);  
GO   
INSERT INTO MyTest (myKey, myValue) VALUES (2, 0);  
GO  

select * from MyTest
Go

update MyTest set myValue = 0 
go

/* row version will have changed */
select * from MyTest
Go

The only choice I have found is to create an update trigger.