Re: Manual Vacuum Analyze Take More Time

On Wed, Nov 28, 2018 at 11:42 AM Moin Akther <moindba(at)hotmail(dot)com> wrote:

> Dear All,
>
> Thanks for your suggestions !
>
> What will be work around to do routine manual “VACUUM ANALYZE” ? If I do
> only analyze on a table does it will generate WAL files ?
>
> If we don’t do frequent “VACUUM ANALYZE” what are the possible impact on
> DB ?
>
> Upgrading to higher version and planning for partitioning require series
> of approval’s and it takes more time to implement.
>
>
> Thanks and Best Regards,
> *Moin Akther*
> Email: moindba(at)hotmail(dot)com
>
>
>
>
Not vacuuming should not be considered an option. Only analyzing just
updates the statistics and does not do necessary maintenance functions on
the table. The longer you let this table go unvacuumed, the worse it's
going to be when it does actually need to be vacuumed. At some point it
will be required for it to be vacuumed. It will cause autovacuum to kick in
a more aggressive vacuum first (look into autovacuum_freeze_max_age) or
your database will shut down (look into transaction ID wraparound). The
other more immediate issue is that queries will start to become slower and
slower as old rows are not being marked as reusable and bloat continues to
grow.

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

If this table hasn't been vacuumed for a very long time, a good chunk of
the size could indeed be due to bloat. I highly recommend using pgstattuple
or the tool discussed in this blog post to check

https://www.keithf4.com/checking-for-postgresql-bloat/
https://www.keithf4.com/cleaning-up-postgresql-bloat/

One thing you could do would be to do the ANALYZE separate from the VACUUM.
That will at least shorten the transaction time since it doesn't have to
wait until the ANALYZE finishes to commit. But then you should do the
ANALYZE soon after the VACUUM finishes.

--
Keith Fiske
Senior Database Engineer
Crunchy Data - http://crunchydata.com