Thread: [Autovacuum] Issue to understand some logs

[Autovacuum] Issue to understand some logs

From
Baptiste LHOSTE
Date:
Hi everybody,

I have trouble understanding some logs of postgreSQL.

Here you can find a log from the auto-vacuum process :

2012-12-17 16:38:58 CET LOG:  automatic vacuum of table "flows.public.agg_t344_outgoing_a41_src_net_and_dst_net_f5":
indexscans: 0 
    pages: 0 removed, 59820 remain
    tuples: 0 removed, 5801752 remain
    system usage: CPU 0.93s/0.95u sec elapsed 423.07 sec

I am right to conclude that there is 5801752 available tuples in the previous table ?

If true, I am very confused because our table can not exceed 2592000 tuples (We delete old ones).

To be sure I tried to run the following query to count availables tuples :

select count(*) from agg_t344_outgoing_a41_src_net_and_dst_net_f5;
  count
---------
 2584398
(1 row)

Can someone give me a clue ?

Best regards,

Baptiste.

---
Baptiste LHOSTE
blhoste@alaloop.com

ALALOOP S.A.S. - Technopole Izarbel - 64210 Bidart
Téléphone : +33 (0) 5 59 41 51 10
www.alaloop.com



Re: [Autovacuum] Issue to understand some logs

From
Guillaume Lelarge
Date:
On Mon, 2012-12-17 at 16:57 +0100, Baptiste LHOSTE wrote:
> Hi everybody,
>
> I have trouble understanding some logs of postgreSQL.
>
> Here you can find a log from the auto-vacuum process :
>
> 2012-12-17 16:38:58 CET LOG:  automatic vacuum of table "flows.public.agg_t344_outgoing_a41_src_net_and_dst_net_f5":
indexscans: 0 
>     pages: 0 removed, 59820 remain
>     tuples: 0 removed, 5801752 remain
>     system usage: CPU 0.93s/0.95u sec elapsed 423.07 sec
>
> I am right to conclude that there is 5801752 available tuples in the previous table ?
>
> If true, I am very confused because our table can not exceed 2592000 tuples (We delete old ones).
>
> To be sure I tried to run the following query to count availables tuples :
>
> select count(*) from agg_t344_outgoing_a41_src_net_and_dst_net_f5;
>   count
> ---------
>  2584398
> (1 row)
>
> Can someone give me a clue ?
>

It could be dead rows, still visible for other transactions.


--
Guillaume
http://blog.guillaume.lelarge.info
http://www.dalibo.com



Re: [Autovacuum] Issue to understand some logs

From
Baptiste LHOSTE
Date:
> It could be dead rows, still visible for other transactions.

Ok but in this case, why the automatic vacuum task of the autovacuum process does not delete theses dead rows ?

Best regards,

Baptiste

---
Baptiste LHOSTE
blhoste@alaloop.com

ALALOOP S.A.S. - Technopole Izarbel - 64210 Bidart
Téléphone : +33 (0) 5 59 41 51 10
www.alaloop.com


Re: [Autovacuum] Issue to understand some logs

From
Guillaume Lelarge
Date:
On Mon, 2012-12-17 at 17:10 +0100, Baptiste LHOSTE wrote:
> > It could be dead rows, still visible for other transactions.
>
> Ok but in this case, why the automatic vacuum task of the autovacuum process does not delete theses dead rows ?
>

As I said, because they are still visible to other transactions. Try to
see if you have long-lasting transactions.


--
Guillaume
http://blog.guillaume.lelarge.info
http://www.dalibo.com



Re: [Autovacuum] Issue to understand some logs

From
Baptiste LHOSTE
Date:
>As I said, because they are still visible to other transactions. Try to
>see if you have long-lasting transactions.

How can I do that ? I check running query in pg_stat_activity, but there is no query on that table.

Best regards,

Baptiste.

---
Baptiste LHOSTE
blhoste@alaloop.com

ALALOOP S.A.S. - Technopole Izarbel - 64210 Bidart
Téléphone : +33 (0) 5 59 41 51 10
www.alaloop.com



Re: [Autovacuum] Issue to understand some logs

From
Baptiste LHOSTE
Date:
I run a select on the pg_stat_all_tables and it returns that there is 0 n_dead_tup.

I am really confused.

Best regards,

Baptiste.

---
Baptiste LHOSTE
blhoste@alaloop.com

ALALOOP S.A.S. - Technopole Izarbel - 64210 Bidart
Téléphone : +33 (0) 5 59 41 51 10
www.alaloop.com


Re: [Autovacuum] Issue to understand some logs

From
Tom Lane
Date:
Baptiste LHOSTE <blhoste@alaloop.com> writes:
>> As I said, because they are still visible to other transactions. Try to
>> see if you have long-lasting transactions.

> How can I do that ? I check running query in pg_stat_activity, but there is no query on that table.

Does "select * from pg_prepared_xacts" find anything?

            regards, tom lane


Re: [Autovacuum] Issue to understand some logs

From
Baptiste LHOSTE
Date:
> Does "select * from pg_prepared_xacts" find anything?

Yes indeed, so I rollback our old prepared transactions.

I will check tomorrow, and I will let you know.

Best regards,

Baptiste.

---
Baptiste LHOSTE
blhoste@alaloop.com

ALALOOP S.A.S. - Technopole Izarbel - 64210 Bidart
Téléphone : +33 (0) 5 59 41 51 10
www.alaloop.com



Re: [Autovacuum] Issue to understand some logs

From
Baptiste LHOSTE
Date:
Thanks both of you for your help.

The autovacuum process did the work yesterday.

Best regards,

Baptiste

---
Baptiste LHOSTE
blhoste@alaloop.com

ALALOOP S.A.S. - Technopole Izarbel - 64210 Bidart
Téléphone : +33 (0) 5 59 41 51 10
www.alaloop.com