Thread: Re: [QUESTIONS] MySQL benchmark page
Nobody likes to take the time to move discussions, do they? And ya, I'm
about as guilty *sigh*
Move to pgsql-hackers@postgresql.org...
On Tue, 3 Feb 1998, Herouth Maoz wrote:
> At 15:01 +0200 on 2/2/98, The Hermit Hacker wrote:
>
> I think the garbage collection should be separated from the statistics.
> Garbage collection needs a write lock, statistics only a read lock. If they
> are not done at the same time, the various tables would be locked for
> shorter periods.
Hrmmmm...good point, I think. Bruce? Vadim? When vacuum'ng a
large table, how much time is spend 'garbage collecting' vs 'statistics'?
I thought that 'vacuum analyze' *was* the statistics aspect of it? Where
just 'vacuum' was only garbage collection...?
> > > > Nobody likes to take the time to move discussions, do they? And ya, I'm > about as guilty *sigh* > > Move to pgsql-hackers@postgresql.org... > > > On Tue, 3 Feb 1998, Herouth Maoz wrote: > > > At 15:01 +0200 on 2/2/98, The Hermit Hacker wrote: > > > > I think the garbage collection should be separated from the statistics. > > Garbage collection needs a write lock, statistics only a read lock. If they > > are not done at the same time, the various tables would be locked for > > shorter periods. > > Hrmmmm...good point, I think. Bruce? Vadim? When vacuum'ng a > large table, how much time is spend 'garbage collecting' vs 'statistics'? > I thought that 'vacuum analyze' *was* the statistics aspect of it? Where > just 'vacuum' was only garbage collection...? This is correct. Vacuum is fast, vacuum analyze is pretty slow. We could separate them, I guess, and that would eliminate the write-lock and be only a readlock. -- Bruce Momjian maillist@candle.pha.pa.us
On Tue, 3 Feb 1998, Bruce Momjian wrote:
> > On Tue, 3 Feb 1998, Herouth Maoz wrote:
> >
> > > At 15:01 +0200 on 2/2/98, The Hermit Hacker wrote:
> > >
> > > I think the garbage collection should be separated from the statistics.
> > > Garbage collection needs a write lock, statistics only a read lock. If they
> > > are not done at the same time, the various tables would be locked for
> > > shorter periods.
> >
> > Hrmmmm...good point, I think. Bruce? Vadim? When vacuum'ng a
> > large table, how much time is spend 'garbage collecting' vs 'statistics'?
> > I thought that 'vacuum analyze' *was* the statistics aspect of it? Where
> > just 'vacuum' was only garbage collection...?
>
> This is correct. Vacuum is fast, vacuum analyze is pretty slow. We
> could separate them, I guess, and that would eliminate the write-lock
> and be only a readlock.
Possible to slip it in for v6.3? Would make it so that an analyze
could be done nightly, to keep statistics up, and then a vacuum once a
week or so just for garbage collection...?
> > This is correct. Vacuum is fast, vacuum analyze is pretty slow. We > > could separate them, I guess, and that would eliminate the write-lock > > and be only a readlock. > > Possible to slip it in for v6.3? Would make it so that an analyze > could be done nightly, to keep statistics up, and then a vacuum once a > week or so just for garbage collection...? When I added analyze, I did not understand the issues, so I was able to work from Vadim's code in vacuum. I put it on the TODO list. Don't know if it can make 6.3. I am working on cleaning up the cacheoffset code right now. -- Bruce Momjian maillist@candle.pha.pa.us