ROWID equivalent in postgres 9.2

Question

Is there any way to get rowid of a record in postgres??

In oracle i can use like

SELECT MAX(BILLS.ROWID) FROM BILLS  

Answer 1

Yes, there is ctid column which is equivalent for rowid. But is useless for you. Rowid and ctid are physical row/tuple identifiers => can change after rebuild/vacuum.

See: Chapter 5. Data Definition > 5.4. System Columns

Answer 2

The PostgreSQL row_number() window function can be used for most purposes where you would use rowid. Whereas in Oracle the rowid is an intrinsic numbering of the result data rows, in Postgres row_number() computes a numbering within a logical ordering of the returned data. Normally if you want to number the rows, it means you expect them in a particular order, so you would specify which column(s) to order the rows when numbering them:

select client_name, row_number() over (order by date) from bills;

If you just want the rows numbered arbitrarily you can leave the over clause empty:

select client_name, row_number() over () from bills;

If you want to calculate an aggregate over the row number you'll have to use a subquery:

select max(rownum) from (
    select row_number() over () as rownum from bills
) r;

If all you need is the last item from a table, and you have a column to sort sequentially, there's a simpler approach than using row_number(). Just reverse the sort order and select the first item:

select * from bills 
order by date desc limit 1;

Answer 3

Use a Sequence. You can choose 4 or 8 byte values.

http://www.neilconway.org/docs/sequences/

Answer 4

Add any unique column to your table(name maybe rowid). And prevent changing it by creating BEFORE UPDATE trigger, which will raise exception if someone will try to update. You may populate this column with sequence as @JohnMudd mentioned.