Re: Using xmin to identify last modified rows

Stéphane A. Schildknecht wrote:
> Trying to identify last modified (updated or inserted) rows in a table, I
> thought I could use xmin.
>
> I tried is to get some lines sorted by xmin.
>
> When doing it on a slonified database, I had no problem getting these lines.
>
> But, trying the same query on a non slonified DB, I got an error, as there is
> no ordering operator for xid.
>
> I think that in the slon case, the query uses the implicit cast xid->xxid, and
> then the operator to sort xxid.
>
> What would be the best way to get last modified rows?
>
> What I tried :
> db=# select id_table, date_table, code_table from tb_table order by xmin desc limit 10;
> ERROR: could not identify an ordering operator for type xid
> ASTUCE : Use an explicit ordering operator or modify the query.

What about:

test=> SELECT xmin, * FROM mausi ORDER BY xmin::text::bigint;
xmin | id | val
-------+----+----------------
14005 | 1 | test\test/test
14040 | 3 | mamma
(2 rows)

Yours,
Laurenz Albe