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

Melvin:

On Tue, Oct 11, 2016 at 8:33 PM, Melvin Davidson <melvin6925(at)gmail(dot)com> wrote:

> FYI, moving between tablespaces requires an exclusive table lock, so it's naturally going to be slow.

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

The lock may lengthen the operation due to potential delays.

And moving between tablespaces on a big db may well be a fast ( speed
) but long ( time ) process, lots of things have to be done, but they
can be done rather fast. But even if light is fast, it still needs 550
years to reach Antares. You can have a short slow operation ( like
needing a second to get an indexed tuple ) or a fast long one ( like
needing an hour to move a petabyte of data ).

To judge if its going slow we will need a reference, like, how much
time does it take to copy and sync a big uncached file between the
affected volumes. If move does say, 1.5 times slower I wouldn't say it
is that slow ( given copy is optimized for this kind of transfers and
a database not so much ).

Francisco Olarte.