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> From: Sriram Dandapani [mailto:[EMAIL PROTECTED] > Most of our reports use a order by limit X...The rowcount in > some tables > are > 200 million. (and the table size is about 50-100gb) > > Does the fact that constraint_exclusion doesn't deal with order by > /limit > makes partitioning an unwise choice. Well, in a worst-case scenario, partitioning will perform no worse than if you had one giant table. So it's not hurting you, it may just not be helping you. > What if the main query does just an order by and an outer query wraps > the inner query with a limit.. It all depends on if the order-by code is partitioning aware, and I'm not sure that it is. But if you index on the appropriate column it should hopefully make use of that... > I am trying to figure out if I should use partitioning or not (my goal > is two-fold..purge lots of data in aged tables and make queries > partition-aware) Well, reason #1 sounds like plenty of justification for using partitioning to me. > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Jim C. Nasby > Sent: Wednesday, April 26, 2006 3:51 PM > To: Chris Hoover > Cc: Benjamin Krajmalnik; [email protected] > Subject: Re: [ADMIN] Tale partitioning > > On Wed, Apr 26, 2006 at 04:33:04PM -0400, Chris Hoover wrote: > > Each of the partition tables needs it's own set of indexes. Build > them, and > > see if the does not fix your performance issues. Also, be sure you > turned > > on the constraint_exclusion parameter, and each table > (other than the > > "master") has an constraint on it that is unique. > > I don't believe constraint_exclusion is smart enough to deal > with ORDER > BY / LIMIT yet... :/ > -- > Jim C. Nasby, Sr. Engineering Consultant [EMAIL PROTECTED] > Pervasive Software http://pervasive.com work: 512-231-6117 > vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461 > > ---------------------------(end of > broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings > ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
