Re: Measuring CPU time use? (Another stupid question)

I suppose I should rephrase.

I am trying to figure out which of two competing ideas of mine is the more
efficient.

Right now, I am running it on a "slow" machine-- a G3/220 with 148MB of
RAM, on OLD SCSI-1/2 hardware. Modern machines have much faster CPUs--
they also have much faster disk tho.

What is important is how long it takes to do a "typical" or "average"
search. I am coding a full-text search system and had two ideas on how to
do it (without implementing my own file-based database, using another
person's, writing stuff in C, or other stuff far more complex than what
the client is paying me for ;) )

So I guess what I'm saying is that I don't care so much about CPU time, or
I/O time, but *TOTAL* time. How long it takes from the instant the query
hits Postgres to the instant I get my results back...

So I need a way to run some 'typical' queries (common search terms for
this system) and figure out which of my algorithms works better... :)

On Wed, 18 Dec 2002, scott.marlowe wrote:

> But you realize that the time it took to run the query is NOT the same as
> the CPU time, right?  A heavy table with 100,000,000 rows may use only a
> tiny percentage of CPU but take a minute to return, while your I/O
> subsystem thrashes away dmaing the data into memory where it gets copied
> to output in 30 milliseconds of CPU time.
>
> Look for iostat to analyze your I/O load, which is often the greater load
> factor for a db server than CPU use.
>
> On Wed, 18 Dec 2002, Jessica Blank wrote:
>
> > Thanky thanky. That might work.
> >
> > Still, I'd rather just have a way I could get a plain old figure.
> >
> > E.g.:
> >
> > DELETE FROM V$CPUUSE;
> > (DO THE QUERIES IN QUESTION HERE)
> > SELECT NANOSECONDS_USED FROM V$CPUUSE;
> >
> > On Wed, 18 Dec 2002, Joe Conway wrote:
> >
> > > Jessica Blank wrote:
> > > > I wish to find a way to measure the CPU time used by any given query (or
> > > > set of queries).
> > > >
> > > > I could not find any information on how to do this...
> > > >
> > > > Is there some secret internal table (like the V$ virtual tables in Oracle)
> > > > that contains this info?
> > >
> > > Well, I don't know of anything specific to CPU usage, but for monitoring your
> > > server see Monitoring Database Activity in the manual:
> > >    http://www.us.postgresql.org/users-lounge/docs/7.3/postgres/monitoring.html
> > >
> > > Also, one of the best and most commonly used tools for optimizing individual
> > > queries is EXPLAIN ANALYZE; see:
> > >    http://www.us.postgresql.org/users-lounge/docs/7.3/postgres/sql-explain.html
> > >
> > > HTH,
> > >
> > > Joe
> > >
> >
> >
>

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