use Benchmark;

$start = new Benchmark;

1 for 1..10000000;

$end = new Benchmark;
$diff = timediff($end, $start);
print "<p>Time taken was ", timestr($diff, 'all'), " seconds\n"; 
__END__

$ perl585 /tmp/p2
<p>Time taken was  4 wallclock secs ( 4.28 usr  0.01 sys +  0.00 cusr 
+ 0.00 csys =  4.29 CPU) seconds
$
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Dave.

I'm astounded because the code I was running was a query of a mysql database with over 12-million rows, pulling out 4,000 rows. In theory, that means the query took less than the 1/100 of a second mimimum displayable? Impressive.

Anyway, thanks.

4,000 rows isn't much for most databases. If you've run the query before, it's likely the database still has the needed pages in cache - it might even have the query, its plan, and the result in cache. And if your database is running on the same machine as the benchmark, results are expected to be fast. Drop your indices, shutdown your database, restart the database, and run your program again. That might give you something to measure.

Well of course nothing's as simple as it should be.

OK - what's this? Shut down the database? I don't recall starting it up. I connected to it - is that what you mean? But I disconnect each time the script terminates.

The benchmark on the same machine as the database? You mean the module?

Drop my indices? The whole point is to measure performance with an index if that's how it's going to run, no?

But the results are odd:

$sql = "SELECT COUNT(*) FROM theTable WHERE column = $value";
$iterations = 1000;
    $sth = $dbh->prepare($sql) or die("Could not prepare!" . $dbh->err
+str);
$exec_time = timethis($iterations, '
    $sth->execute() or die("Could not execute!" . $dbh->errstr);
    $count = $sth->fetchrow_array(  );
');
[download]

timethis 1000: 26 wallclock secs ( 0.03 usr + 0.02 sys = 0.05 CPU) @ 20000.00/s (n=1000) (warning: too few iterations for a reliable count)

26 wallclock seconds but only 0.05 CPU seconds? And if I try to go to 5,000 iterations, the server returns an error.