Re: The age() of a column?

On 11/28/18 7:32 PM, Ron wrote:
> What does it mean, and where is it documented?  The only place in the

https://www.postgresql.org/docs/10/routine-vacuuming.html

"The age column measures the number of transactions from the cutoff XID
to the current transaction's XID."

> docs I see reference to age() is
> https://www.postgresql.org/docs/9.6/functions-datetime.html and this
> doesn't seem to fit that use case.
>
> Thanks
>
> TAPb=# select COALESCE(ta.schemaname, 'pg_toast') || '.' || cl.relname,
>        cl.relfrozenxid,
>        age(cl.relfrozenxid)
> from pg_class cl FULL JOIN pg_tables ta
>     ON ta.tablename = cl.relname
> where not cl.relfrozenxid = xid '0'
>   --and age(cl.relfrozenxid) > 4000000
> order by 1
> limit 30;
>            ?column?            | relfrozenxid |   age
> -------------------------------+--------------+---------
> cds.ach_return_batch           |     58569152 | 2111005
> cds.ach_return_detail          |     58569152 | 2111005
> cds.all_day_event              |     58569152 | 2111005
> cds.all_day_event_trigger      |     58569152 | 2111005
> [snip]
> cds.bank_ftp                   |     58569152 | 2111005
> cds.bank_health_care_job       |     58569152 | 2111005
> cds.bank_inbound_file          |     58569152 | 2111005
> cds.bank_input_format          |     58569152 | 2111005
> (30 rows)
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com