Re: [PERFORM] Slow vacuum performance
On Thu, 2004-06-17 at 13:09 -0700, Patrick Hatcher wrote: Pg: 7.4.2 RedHat 7.3 Ram: 8gig I have 6 million row table that I vacuum full analyze each night. The time seems to be streching out further and further as I add more rows. I read the archives and Josh's annotated pg.conf guide that setting the FSM higher might help. Currently, my memory settings are set as such. Does this seem low? Last reading from vaccum verbose: INFO: analyzing cdm.cdm_ddw_customer INFO: cdm_ddw_customer: 209106 pages, 3000 rows sampled, 6041742 estimated total rows I think I should now set my max FSM to at least 21 but wanted to make sure Yes, that's my interpretation of those numbers too. I would set max_fsm_pages to 30 (or more) in that case. If you have 8G of RAM in the machine your shared_buffers seems very low too. Depending on how it is used I would increase that to at least the recommended maximum (1 - 80M). You don't quote your setting for effective_cache_size, but you should probably look at what /usr/bin/free reports as cached, divide that by 10, and set it to that as a quick rule of thumb... Regards, Andrew McMillan shared_buffers = 2000 # min 16, at least max_connections*2, 8KB each sort_mem = 12288# min 64, size in KB # - Free Space Map - max_fsm_pages = 10 # min max_fsm_relations*16, 6 bytes each #max_fsm_relations = 1000 # min 100, ~50 bytes each - Andrew @ Catalyst .Net .NZ Ltd, PO Box 11-053, Manners St, Wellington WEB: http://catalyst.net.nz/PHYS: Level 2, 150-154 Willis St DDI: +64(4)803-2201 MOB: +64(272)DEBIAN OFFICE: +64(4)499-2267 Make things as simple as possible, but no simpler -- Einstein - signature.asc Description: This is a digitally signed message part
[PERFORM] Slow vacuum performance
Pg: 7.4.2 RedHat 7.3 Ram: 8gig I have 6 million row table that I vacuum full analyze each night. The time seems to be streching out further and further as I add more rows. I read the archives and Josh's annotated pg.conf guide that setting the FSM higher might help. Currently, my memory settings are set as such. Does this seem low? Last reading from vaccum verbose: INFO: analyzing cdm.cdm_ddw_customer INFO: cdm_ddw_customer: 209106 pages, 3000 rows sampled, 6041742 estimated total rows I think I should now set my max FSM to at least 21 but wanted to make sure shared_buffers = 2000 # min 16, at least max_connections*2, 8KB each sort_mem = 12288# min 64, size in KB # - Free Space Map - max_fsm_pages = 10 # min max_fsm_relations*16, 6 bytes each #max_fsm_relations = 1000 # min 100, ~50 bytes each TIA Patrick Hatcher Macys.Com ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
[PERFORM] slow vacuum performance
Hi, I am running pg 7.4.1 on linux box. I have a midle size DB with many updates and after it I try to run vacuum full analyze. It takes about 2 h. If I try to dump and reload the DB it take 20 min. How can I improve the vacuum full analyze time? My configuration: shared_buffers = 15000 # min 16, at least max_connections*2, 8KB each sort_mem = 1# min 64, size in KB vacuum_mem = 32000 # min 1024, size in KB effective_cache_size = 4# typically 8KB each #max_fsm_pages = 2 # min max_fsm_relations*16, 6 bytes each #max_fsm_relations = 1000 # min 100, ~50 bytes each regards, ivan. ---(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
Re: [PERFORM] slow vacuum performance
pginfo wrote: Hi, I am running pg 7.4.1 on linux box. I have a midle size DB with many updates and after it I try to run vacuum full analyze. It takes about 2 h. If I try to dump and reload the DB it take 20 min. How can I improve the vacuum full analyze time? How often are you vacuuming? If you've gone a LONG time since the last vacuum, it can take quite a while, to the point where a dump/restore is faster. A recent realization that I've had some misconceptions about vacuuming led me to re-read section 8.2 of the admin guide (on vacuuming) ... I highly suggest a review of these 3 pages of the admin manual, as it contains an excellent description of why databases need vacuumed, that one can use to determine how often vacuuming is necessary. -- Bill Moran Potential Technologies http://www.potentialtech.com ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED])
Re: [PERFORM] slow vacuum performance
Hi Bill, I am vacuuming every 24 h. I have a cron script about i. But if I make massive update (for example it affects 1 M rows) and I start vacuum, it take this 2 h. Also I will note, that this massive update is running in one transaction ( I can not update 100K and start vacuum after it). regards, ivan. Bill Moran wrote: pginfo wrote: Hi, I am running pg 7.4.1 on linux box. I have a midle size DB with many updates and after it I try to run vacuum full analyze. It takes about 2 h. If I try to dump and reload the DB it take 20 min. How can I improve the vacuum full analyze time? How often are you vacuuming? If you've gone a LONG time since the last vacuum, it can take quite a while, to the point where a dump/restore is faster. A recent realization that I've had some misconceptions about vacuuming led me to re-read section 8.2 of the admin guide (on vacuuming) ... I highly suggest a review of these 3 pages of the admin manual, as it contains an excellent description of why databases need vacuumed, that one can use to determine how often vacuuming is necessary. -- Bill Moran Potential Technologies http://www.potentialtech.com ---(end of broadcast)--- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
Re: [PERFORM] slow vacuum performance
On Wed, 24 Mar 2004, pginfo wrote: Hi, I am running pg 7.4.1 on linux box. I have a midle size DB with many updates and after it I try to run vacuum full analyze. Is there a reason to not use just regular vacuum / analyze (i.e. NOT full)? It takes about 2 h. Full vacuums, by their nature, tend to be a bit slow. It's better to let the database achieve a kind of steady state with regards to number of dead tuples, and use regular vacuums to reclaim said space rather than a full vacuum. How can I improve the vacuum full analyze time? My configuration: shared_buffers = 15000 # min 16, at least max_connections*2, 8KB each sort_mem = 1# min 64, size in KB You might want to look at dropping sort_mem. It would appear you've been going through the postgresql.conf file and bumping up numbers to see what works and what doesn't. While most of the settings aren't too dangerous to crank up a little high, sort_mem is quite dangerous to crank up high, should you have a lot of people connected who are all sorting. Note that sort_mem is a limit PER SORT, not per backend, or per database, or per user, or even per table, but per sort. IF a query needs to run three or four sorts, it can use 3 or 4x sort_mem. If a hundred users do this at once, they can then use 300 or 400x sort_mem. You can see where I'm heading. Note that for individual sorts in batch files, like import processes, you can bump up sort_mem with the set command, so you don't have to have a large setting in postgresql.conf to use a lot of sort mem when you need to, you can just grab it during that one session. vacuum_mem = 32000 # min 1024, size in KB If you've got lots of memory, crank up vacuum_mem to the 200 to 500 meg range and see what happens. For a good tuning guide, go here: http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED])
Re: [PERFORM] slow vacuum performance
Hi, scott.marlowe wrote: On Wed, 24 Mar 2004, pginfo wrote: Hi, I am running pg 7.4.1 on linux box. I have a midle size DB with many updates and after it I try to run vacuum full analyze. Is there a reason to not use just regular vacuum / analyze (i.e. NOT full)? Yes, in case I make massive updates (only in my case of cource) for example 2 M rows, I do not expect to have 2M new rows in next 180 days.That is the reaso for running vacuum full. My idea was to free unneedet space and so to have faster system. It is possible that I am wrong. It takes about 2 h. Full vacuums, by their nature, tend to be a bit slow. It's better to let the database achieve a kind of steady state with regards to number of dead tuples, and use regular vacuums to reclaim said space rather than a full vacuum. How can I improve the vacuum full analyze time? My configuration: shared_buffers = 15000 # min 16, at least max_connections*2, 8KB each sort_mem = 1# min 64, size in KB You might want to look at dropping sort_mem. It would appear you've been going through the postgresql.conf file and bumping up numbers to see what works and what doesn't. While most of the settings aren't too dangerous to crank up a little high, sort_mem is quite dangerous to crank up high, should you have a lot of people connected who are all sorting. Note that sort_mem is a limit PER SORT, not per backend, or per database, or per user, or even per table, but per sort. IF a query needs to run three or four sorts, it can use 3 or 4x sort_mem. If a hundred users do this at once, they can then use 300 or 400x sort_mem. You can see where I'm heading. Note that for individual sorts in batch files, like import processes, you can bump up sort_mem with the set command, so you don't have to have a large setting in postgresql.conf to use a lot of sort mem when you need to, you can just grab it during that one session. I know. In my case we are using many ID's declared as varchar/name (I know it is bad idea, butwe are migrating this system from oracle) and pg have very bad performance with varchar/name indexes. The only solution I found was to increase the sort mem. But, I wll try to decrease this one and to see the result. vacuum_mem = 32000 # min 1024, size in KB If you've got lots of memory, crank up vacuum_mem to the 200 to 500 meg range and see what happens. I wil try it today. It is good idea and hope it will help. For a good tuning guide, go here: http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html I know it. It is the best I found and also the site. Thanks for the help. ivan. ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED])
Re: [PERFORM] slow vacuum performance
On Wed, 24 Mar 2004, pginfo wrote: Hi, scott.marlowe wrote: On Wed, 24 Mar 2004, pginfo wrote: Hi, I am running pg 7.4.1 on linux box. I have a midle size DB with many updates and after it I try to run vacuum full analyze. Is there a reason to not use just regular vacuum / analyze (i.e. NOT full)? Yes, in case I make massive updates (only in my case of cource) for example 2 M rows, I do not expect to have 2M new rows in next 180 days.That is the reaso for running vacuum full. My idea was to free unneedet space and so to have faster system. It is possible that I am wrong. It's all about percentages. If you've got an average of 5% dead tuples with regular vacuuming, then full vacuums won't gain you much, if anything. If you've got 20 dead tuples for each live one, then a full vacuum is pretty much a necessity. The generally accepted best performance comes with 5 to 50% or so dead tuples. Keep in mind, having a few dead tuples is actually a good thing, as your database won't grow then srhink the file all the time, but keep it in a steady state size wise. ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
Re: [PERFORM] slow vacuum performance
scott.marlowe wrote: On Wed, 24 Mar 2004, pginfo wrote: Hi, scott.marlowe wrote: On Wed, 24 Mar 2004, pginfo wrote: Hi, I am running pg 7.4.1 on linux box. I have a midle size DB with many updates and after it I try to run vacuum full analyze. Is there a reason to not use just regular vacuum / analyze (i.e. NOT full)? Yes, in case I make massive updates (only in my case of cource) for example 2 M rows, I do not expect to have 2M new rows in next 180 days.That is the reaso for running vacuum full. My idea was to free unneedet space and so to have faster system. It is possible that I am wrong. It's all about percentages. If you've got an average of 5% dead tuples with regular vacuuming, then full vacuums won't gain you much, if anything. If you've got 20 dead tuples for each live one, then a full vacuum is pretty much a necessity. The generally accepted best performance comes with 5 to 50% or so dead tuples. Keep in mind, having a few dead tuples is actually a good thing, as your database won't grow then srhink the file all the time, but keep it in a steady state size wise. thanks for the good analyze,ivan. ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED])
