I do have one table that acts as a lookup table and grows in size as the app runs, however in the tests I have been doing I have dropped and recreated all tables including the lookup table.
I keep wondering how disk is allocated to a particular DB. Also is there any way I could tell whether the writes to disk are the bottleneck? T.R. Missner Level(3) Communications SSID tools Senior Software Engineer -----Original Message----- From: Matthew T. O'Connor [mailto:[EMAIL PROTECTED] Sent: Wednesday, July 07, 2004 1:17 PM To: Missner, T. R. Cc: [EMAIL PROTECTED] Subject: Re: [PERFORM] inserting into brand new database faster than old database I don't think I have enough detail about your app. Couple of questions, are there any tables that recieve a lot of inserts / updates / deletes that are not deleted and recreated often? If so, one possibility is that you don't have a large enough FSM settings and your table is actually growing despite using autovac. Does that sounds possbile to you? Missner, T. R. wrote: > Hello, > > I have been a happy postgresql developer for a few years now. Recently > I have discovered a very strange phenomenon in regards to inserting > rows. > > My app inserts millions of records a day, averaging about 30 rows a > second. I use autovac to make sure my stats and indexes are up to date. > Rarely are rows ever deleted. Each day a brand new set of tables is > created and eventually the old tables are dropped. The app calls > functions which based on some simple logic perform the correct inserts. > > > The problem I am seeing is that after a particular database gets kinda > old, say a couple of months, performance begins to degrade. Even after > creating brand new tables my insert speed is slow in comparison ( by a > magnitude of 5 or more ) with a brand new schema which has the exact > same tables. I am running on an IBM 360 dual processor Linux server > with a 100 gig raid array spanning 5 scsi disks. The machine has 1 gig > of ram of which 500 meg is dedicated to Postgresql. > > Just to be clear, the question I have is why would a brand new db schema > allow inserts faster than an older schema with brand new tables? Since > the tables are empty to start, vacuuming should not be an issue at all. > Each schema is identical in every way except the db name and creation > date. > > Any ideas are appreciated. > > Thanks, > > T.R. Missner > > ---------------------------(end of broadcast)--------------------------- > TIP 9: the planner will ignore your desire to choose an index scan if your > joining column's datatypes do not match > ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
