Re: My DB has has 5TB, many operations are very slow (on Google Cloud Compute)

On Tue, Oct 11, 2016 at 3:16 PM, Francisco Olarte <folarte(at)peoplecall(dot)com>
wrote:

> Rakesh:
>
> On Tue, Oct 11, 2016 at 9:00 PM, Rakesh Kumar
> <rakeshkumar464(at)outlook(dot)com> wrote:
> >>Cores do not help, postgres is single-threaded. RAM MAY help, but I
> > I hope this is no longer true from 9.6 for those queries where PG can
> use parallelism.
>
> It does, AFAIK, but for queries, not AFAIK for this kind of data
> moving ops ( and I doubt it will, as presently you can easily saturate
> the channels with a single core for that kind of simple ops, and
> normally if you want to optimize this kind of op is better to target
> concurrency ( table can be used while moving ) than pure speed .
>
> Francisco Olarte.
>

>Requiring and exclusive table lock does not imply slownes. Just try
>'lock table x in exclusive mode' on an idle system. Pretty fast.

Sure on an idle system, you will get a table lock right away, but OP's
statements imply a large busy system.
And if there are transactions occurring against that table, there is no
telling how long it will take. Since we
do not have enough specific info, I stand by my statement.

--
*Melvin Davidson*
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.