[EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
: Charles K. Clarkson [CKC], on Friday, November 26, 2004 at
: 05:30 (-0600) has on mind:
:
: : It would be slower and less accurate. To use your
: : suggestion would require another query on the database.
: : That count might also not return the same count as is
: : in "scalar @$rows" if the database is updated between
: : queries.
:
: hm, I did some benchmarks and it seems I'm right, I use
: something like:
:
: ...
: $start = new Benchmark;
: for (1 .. 1000) {
: $sth = $dbh->prepare_cached(
: 'SELECT COUNT(sessionid) FROM session' );
: $sth->execute();
: $result = $sth->fetchrow_array();
: $sth->finish;
: }
: $end = new Benchmark;
:
: $diff = timediff($end, $start);
: print "Time taken was ", timestr($diff, 'all'), " seconds\n\n";
: ...
:
: and it was definitely faster, than your suggestion. Did
: you try some benchmarking?
I timed the two ideas with logic. Here's the method I
presented.
my $rows = $dbh->selectall_arrayref(
'SELECT sessionid FROM session'
);
my $row_count = @$rows;
Here's the method you presented.
my $rows = $dbh->selectall_arrayref(
'SELECT sessionid FROM session'
);
my $row_count = $dbh->do(
'SELECT COUNT(sessionid) FROM session' );
The difference between the two methods is the second
statement.
my $row_count = @$rows;
vs.
my $row_count = $dbh->do(
'SELECT COUNT(sessionid) FROM session' );
Do you really believe that DBI will make a second
call to the database faster than perl can return the size
of an array in memory?
Now, let's say someone updates the database between
calls, on a busy web site those two queries might
accurately report different table sizes.
HTH,
Charles K. Clarkson
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