Обсуждение: autovacuum on updated rows

I am looking at the file sizes that correspond to this table and its indeces.  They are growing -- I think I understand why -- dead rows are occuring on an UPDATE.  But what I don't understand is why autovacuum has not kicked in-- I have kept the default values on autovacuum.

In about 50 minutes' time, the table itself has grown 2MB, and each index has grown by about 1MB

On 11/11/05, Stephen Byers <stephenabyers@yahoo.com> wrote:
> I am using new postgres 8.1 and also trying out the integrated autovacuum.
> I have a concern.
>
> I have a table where I perform an update on a row every 10 seconds.  The
> table is VERY small.  Hardly any INSERTS, no DELETES, and a ton of UPDATES.
>
> adbs_db=# select count(*) from volumes;
>  count
> -------
>      7
> (1 row)
>
>
>
>
>
> I am looking at the file sizes that correspond to this table and its
> indeces.  They are growing -- I think I understand why -- dead rows are
> occuring on an UPDATE.  But what I don't understand is why autovacuum has
> not kicked in-- I have kept the default values on autovacuum.
>
>

i will assume you change #autovacuum=off for on in postgresql.conf you
have to activet stats_stat_collector and stats_row_level too...

here explains what factors are used for determining vacuum needs for
tables: http://www.postgresql.org/docs/8.1/static/maintenance.html#AUTOVACUUM


>
> In about 50 minutes' time, the table itself has grown 2MB, and each index
> has grown by about 1MB
>
> Will autovacuum eventually run on this table????  What rows/columns does
> autovacuum look at to determine when to work on a table?  I'd like to look
> at those rows, too.
>
> Thanks!!
> Steve
>
>
> adbs_db=# \d volumes
>                      Table "public.volumes"
>       Column      |          Type          |     Modifiers
> ------------------+------------------------+--------------------
>  label            | character varying(128) | not null
>  imported         | boolean                | not null
>  closed           | boolean                | not null
>  active           | boolean                | not null
>  online           | boolean                | not null
>  offline          | boolean                | not null
>  archiver_name    | character varying(32)  | not null
>  environment_name | character varying(32)  | not null
>  curr_size        | bigint                 | not null default 0
>  vol_num          | integer                | not null
>  start_time       | integer                |
>  stop_time        | integer                |
> Indexes:
>     "volumes_i1" unique, btree (label)
>     "volumes_i2" btree (environment_name)
>
>

--
Atentamente,
Jaime Casanova
(DBA: DataBase Aniquilator ;)

Stephen Byers <stephenabyers@yahoo.com> writes:
> Will autovacuum eventually run on this table????

Um ... is autovacuum actually turned on?  (It's not by default.)

Check the pg_stat_ views to see if the updates are getting counted in
the statistics for the table.

            regards, tom lane

Stephen Byers writes:
> Will autovacuum eventually run on this table????

Um ... is autovacuum actually turned on? (It's not by default.)

Check the pg_stat_ views to see if the updates are getting counted in
the statistics for the table.

regards, tom lane

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Stephen Byers wrote:
> Sorry for noise.  It turns out that little pound sign in front bit me !!
> #autovacuum = on

So, does it work after you activate it?  Please note that there's a
threshold in the number of tuples that will need to be modified for
a vacuum operation to be launched.  For such a small table you may want
to lower the threshold a bit.  See the docs on the pg_autovacuum system
catalog, in the "internals" chapter.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support