On Mon, 2010-06-07 at 20:10 +0100, Martin Simmons wrote:
> >>>>> On Mon, 7 Jun 2010 18:24:34 +0200, Florian Heigl said:
> > 
> > Hi all,
> > 
> > > Within psql/mysql:
> > > 1) select count(*) from File;                    1sec    30min
> > 
> > Disclaimer: I don't know a dime's worth of databases per se. But I
> > spend a lot of time hunting other peoples performance issues. :)
> > 
> > I think you should start identifying the cause for this bit at the
> > very first, as it shows the absolutely worst perfomance and probably
> > what slows this also slows the rest.
> > My nose says this is really smelly and should'nt even take as long
> > without any indexes.
> 
> Is counting all rows ever fast on postgres?  For me, it runs a sequential
> scan, which is always slow.  It is probably never done with millions of rows
> in a real application, so noone has optimized it.
> 

It runs a sequential scan because of MVCC. Please see 
http://wiki.postgresql.org/wiki/Slow_Counting

I don't know MySQL very well, but I imagine that a count(*) on an InnoDB
database should be as slow

> __Martin
> 
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