Re: [SQL] Joining bug????
От | Howie |
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Тема | Re: [SQL] Joining bug???? |
Дата | |
Msg-id | Pine.LNX.3.96.981027184101.589F-100000@brap-eth0.toodarkpark.org обсуждение исходный текст |
Ответ на | Re: [SQL] Joining bug???? ("Gene Selkov Jr." <selkovjr@mcs.anl.gov>) |
Ответы |
Re: [SQL] Joining bug????
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Список | pgsql-sql |
On Mon, 26 Oct 1998, Gene Selkov Jr. wrote: > > > I've been attempting to get my DB tuned to handle joins as best as > > possible. However, no matter which way I try to perform the joins, if I > > attempt to join more than two or three tables the joins becomes > > unbearably long not matter how many indexes I create in however many ways. > > Ditto. Never saw a quadruple join succeed, even with relatively small tables. Ive been playing with the idea of moving a client from MySQL to Postgres ( views, triggers, and subselects would _really_ make my life easier ). ---[ CUT ]--- SELECT account.accnum, account.accname, ((customers.firstname || ' ') || customers.lastname) as Customer, acctype.descr, account.balance, account.status, billdate.next FROM account,customers,acctype,billdate WHERE account.custnum=customers.custnum AND account.acctype=acctype.accid AND account.accnum=billdate.accnum AND account.accnum<20 ORDER BY account.accnum ---[ CUT ]--- works perfectly, takes about 2 seconds to complete. granted i have ( sometimes unique ) indexes on all the join columns. account has 7k rows, customers has 5k rows, acctype has 12 rows, billdate has 7k rows. a somewhat modified, real-world query ends up crashing postgres, though: ---[ CUT ]--- select account.accnum, account.accname, account.totalfee, billdate.next, ((customers.firstname || ' ') || customers.lastname) as Customer, customers.company, customers.street, acctype.yearly FROM account,customers,acctype,billdate where account.totalfee>0.00 AND billtype=1 OR (billcc1stmo=1 AND account.created=billdate.last) AND balance<>0.00 AND billdate.next>='1998-01-01' AND billdate.next<='1998-01-05' AND account.status<>'C' AND billdate.accnum=account.accnum AND account.custnum=customers.custnum AND account.acctype=acctype.accid ---[ CUT ]--- > > My only solution was to create a hybrid table that contains the join of > > all of the tables I'm searching on with multi-keyed indexes. This is a > > VERY kludgy solution that makes changing the keys to my DB hard to change. > > The solution I use may be the worst imaginable kludge, but it works > great: I do the joins (as well as other set operations) on the client > side. Perl hashes are very good for that. try making a view. from what others have said, views save the query plan and have usually, at least for me, been _alot_ faster than normal queries. --- Howie <caffeine@toodarkpark.org> URL: http://www.toodarkpark.org "Oh my god, they killed init! YOU BASTARDS!"
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