Jeremy Zawodny wrote:
> On Sat, Oct 20, 2001 at 05:02:22PM +0100, Mark Maunder wrote:
> >
> > The only time you'll see a real performance increase is where you're
> > repeadedly calling execute() on the same statement handle with
> > different values for the placeholders - usually this occurs in a
> > loop. This will save you having to do a repeated prepare()
>
> Right.
>
> > so the database server can reuse the old execution plan. Let me know
> > if you want a example.
>
> That's true for some database servers but not MySQL (yet).
I wasn't aware of that - thanks Jeremy. Any ETA as to when this might be
implemented? (part of version 4?) Also just out of curiousity, how much of a
performance hit does mysql take in compiling an execution plan?
tnx!
ps: Here's that example anyway for future ref:
use DBI;
open(FH, "<emails.txt") || die "couldnt open file\n";
my $content;
{
local $/;
$content = <FH>; #slurp
}
close(FH);
$content =~ s/\r\n/\n/g; #in case it's a dos file
my @email_list = split("\n", $content); #assumes 1 email addr per line
my $dbh = DBI->connect("DBI:mysql:dbname:hostname:3306, 'root' ,'password');
my $sth = $dbh->prepare("select (name, address1) from users where email=?");
foreach my $email (@email_list) #email_list loaded from file or something
{
$sth->execute($email); #shorthand for bind_param, same effect
my ($name, $addr1) = $sth->fetchrow();
print "$name - $addr1\n";
}
$sth->finish();
$dbh->disconnect();
#Something like that anyway.
#Creating the initial DB connection has a higher performance impact than
creating an execution plan, so
# something else (more significant) you should look at is optimising your code
by either
# using a global $DBH that everyone shares, or you could
# use something like Apache::DBI for persistent connections under mod_perl if
you're writing a web app which
# will give you a major performance increase.
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