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$dbh->prepare() and execute() take too long?

by jbrugger (Parson)
on Mar 07, 2006 at 06:41 UTC ( #534840=perlquestion: print w/ replies, xml ) Need Help??
jbrugger has asked for the wisdom of the Perl Monks concerning the following question:

Oh wise Perl magicians

I have a query that looks something like this :
select ra.value, ra.ra_id, q.id as q_id, q.qid , q.parent, q.q, q.type +, p.qid as pqid, if($ifstatement,'1','0') as selection , r.rpid from +r, ra, q left join q p on q.parent = p.id where r.id = ra.ra_id and r +.q in (3,4,5) and ra.q = q.id order by ra.ra_id ASC,selection desc;
The 'explain' shows a good and nice run (no full table scans), and in mySQL it takes about 3 seconds to run (about 130.000 records) using  mysql -u user -p database < q.sql > output.txt
When doing this from whithin Perl however,
my $bm= DEBUG_Benchmark->new(); $bm->bmStart(); $sth = $dbh->prepare("select ra.value, ra.ra_id, q.id as q_id, q.qid , + q.parent, q.q, q.type, p.qid as pqid, if($ifstatement,'1','0') as se +lection , r.rpid from r, ra, q left join q p on q.parent = p.id where + r.id = ra.ra_id and r.q in (3,4,5) and ra.q = q.id order by ra.ra_id + ASC,selection desc"); $sth->execute(); $bm->bmStop(); print $bm->getBmResult();
It takes about 12 seconds to run (Only the prepare and the execute, i did not even loop over the resultset).
Any idea on how to speed this up? Whit a smaller resultset, it takes about .003 seconds to prepare / execute.
I know DBI should be able to do mutch better, any ideas on how i can get a better result?
Thanks.

ps.
I run this on an UML (user mode linux), so there is a lot of overhead in the disk io, however, the same problem occurs on a 'normal' debian distribution, the difference is big. (2 sec - 8 sec)

ps.ps.
The resultset of the query looks like this:
value ra_id q_id qid parent q(4,5,6)type pqid sel +ection rpid 1 5501 1918917 34 0 4 6 NULL 1 ed94d62745f5 +2f83cc6225c46cd1f012 1 5501 1918918 33 0 4 6 NULL 1 ed94d62745f5 +2f83cc6225c46cd1f012 4 5501 1918915 32 0 4 6 NULL 1 ed94d62745f5 +2f83cc6225c46cd1f012 2 5501 1918940 31 0 4 6 NULL 1 ed94d62745f5 +2f83cc6225c46cd1f012 6 5501 1918916 30 0 4 6 NULL 1 ed94d62745f5 +2f83cc6225c46cd1f012 ...
*** UPDATE ***
Ah FOUND IT!!! Here is the answer!!!
"We all agree on the necessity of compromise. We just can't agree on when it's necessary to compromise." - Larry Wall.

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