Re: [PERFORM] Low Performance for big hospital server ..
Today is the first official day of this weeks and the system run better in serveral points but there are still some points that need to be corrected. Some queries or some tables are very slow. I think the queries inside the programe need to be rewrite. Now I put the sort mem to a little bit bigger: sort mem = 16384 increase the sort mem makes no effect on the slow point eventhough there is little connnection. shared_buffers = 27853 effective cache = 12 I will put more ram but someone said RH 9.0 had poor recognition on the Ram above 4 Gb? Should I close the hyperthreading ? Would it make any differnce between open and close the hyperthreading? Thanks for any comment Amrit Thailand ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [PERFORM] Low Performance for big hospital server ..
On Tue, 4 Jan 2005 [EMAIL PROTECTED] wrote: Today is the first official day of this weeks and the system run better in serveral points but there are still some points that need to be corrected. Some queries or some tables are very slow. I think the queries inside the programe need to be rewrite. Now I put the sort mem to a little bit bigger: sort mem = 16384 increase the sort mem makes no effect on the slow point eventhough there is little connnection. shared_buffers = 27853 effective cache = 12 Even though others have said otherwise, I've had good results from setting sort_mem higher -- even if that is per query. I will put more ram but someone said RH 9.0 had poor recognition on the Ram above 4 Gb? I think they were refering to 32 bit architectures, not distributions as such. Should I close the hyperthreading ? Would it make any differnce between open and close the hyperthreading? Thanks for any comment In my experience, the largest performance increases come from intensive analysis and optimisation of queries. Look at the output of EXPLAIN ANALYZE for the queries your application is generating and see if they can be tuned in anyway. More often than not, they can. Feel free to ask for assistence on irc at irc.freenode.net #postgresql. People there help optimise queries all day ;-). Amrit Thailand Gavin ---(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] Very Bad Performance.
Dave Cramer wrote: Well, it's not quite that simple the rule of thumb is 6-10% of available memory before postgres loads is allocated to shared_buffers. then effective cache is set to the SUM of shared_buffers + kernel buffers Then you have to look at individual slow queries to determine why they are slow, fortunately you are running 7.4 so you can set log_min_duration to some number like 1000ms and then try to analyze why those queries are slow. I had that already set on my database , and when i look at the log for all the problem queries, most of the queries are slow from one of the table. when i look at the stats on that table they are really wrong, not sure how to fix them. i run vacuumdb and analyze daily. Also hyperthreading may not be helping you.. does it do any harm to the system if it is hyperthreaded ? Dave Pallav Kalva wrote: Hi , I am experiencing a very bad performance on my production database lately , all my queries are slowing down. Our application is a webbased system with lot of selects and updates. I am running vacuumdb daily on all the databases, are the below postgres configuration parameters are set properly ? can anyone take a look. Let me know if you need anymore information. Postgres Version: 7.4 Operating System: Linux Red Hat 9 Cpus: 2 Hyperthreaded RAM: 4 gb Postgres Settings: max_fsm_pages | 2 max_fsm_relations | 1000 shared_buffers | 65536 sort_mem | 16384 vacuum_mem| 32768 wal_buffers| 64 effective_cache_size | 393216 Thanks! Pallav ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [PERFORM] query rewrite using materialized views
Yann, are there any plans for rewriting queries to preexisting materialized views? I mean, rewrite a query (within the optimizer) to use a materialized view instead of the originating table? Automatically, and by default, no. Using the RULES system? Yes, you can already do this and the folks on the MattView project on pgFoundry are working to make it easier. -- Josh Berkus Aglio Database Solutions San Francisco ---(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] query rewrite using materialized views
All, I am currently working on a project for my company that entails Databasing upwards of 300 million specific parameters. In the current DB Design, these parameters are mapped against two lookup tables (2 million, and 1.5 million respectively) and I am having extreme issues getting PG to scale to a working level. Here are my issues: 1)the 250 million records are currently whipped and reinserted as a daily snapshot and the fastest way I have found COPY to do this from a file is no where near fast enough to do this. SQL*Loader from Oracle does some things that I need, ie Direct Path to the db files access (skipping the RDBMS), inherently ignoring indexing rules and saving a ton of time (Dropping the index, COPY'ing 250 million records, then Recreating the index just takes way too long). 2)Finding a way to keep this many records in a fashion that can be easily queried. I even tried breaking it up into almost 2800 separate tables, basically views of the data pre-broken down, if this is a working method it can be done this way, but when I tried it, VACUUM, and the COPY's all seemed to slow down extremely. If there is anyone that can give me some tweak parameters or design help on this, it would be ridiculously appreciated. I have already created this in Oracle and it works, but we don't want to have to pay the monster if something as wonderful as Postgres can handle it. Ryan Wager -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Josh Berkus Sent: Tuesday, January 04, 2005 12:06 PM To: pgsql-performance@postgresql.org Cc: Yann Michel Subject: Re: [PERFORM] query rewrite using materialized views Yann, are there any plans for rewriting queries to preexisting materialized views? I mean, rewrite a query (within the optimizer) to use a materialized view instead of the originating table? Automatically, and by default, no. Using the RULES system? Yes, you can already do this and the folks on the MattView project on pgFoundry are working to make it easier. -- Josh Berkus Aglio Database Solutions San Francisco ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED]) ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [PERFORM] query rewrite using materialized views
1)the 250 million records are currently whipped and reinserted as a daily snapshot and the fastest way I have found COPY to do this from a file is no where near fast enough to do this. SQL*Loader from Oracle does some things that I need, ie Direct Path to the db files access (skipping the RDBMS), inherently ignoring indexing rules and saving a ton of time (Dropping the index, COPY'ing 250 million records, then Recreating the index just takes way too long). If you have the hardware for it, instead of doing 1 copy, do 1 copy command per CPU (until your IO is maxed out anyway) and divide the work amongst them. I can push through 100MB/sec using methods like this -- which makes loading 100GB of data much faster. Ditto for indexes. Don't create a single index on one CPU and wait -- send off one index creation command per CPU. 2)Finding a way to keep this many records in a fashion that can be easily queried. I even tried breaking it up into almost 2800 separate tables, basically views of the data pre-broken down, if this is a working method it can be done this way, but when I tried it, VACUUM, and the COPY's all seemed to slow down extremely. Can you send us EXPLAIN ANALYSE output for the slow selects and a little insight into what your doing? A basic table structure, and indexes involved would be handy. You may change column and table names if you like. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Josh Berkus Sent: Tuesday, January 04, 2005 12:06 PM To: pgsql-performance@postgresql.org Cc: Yann Michel Subject: Re: [PERFORM] query rewrite using materialized views Yann, are there any plans for rewriting queries to preexisting materialized views? I mean, rewrite a query (within the optimizer) to use a materialized view instead of the originating table? Automatically, and by default, no. Using the RULES system? Yes, you can already do this and the folks on the MattView project on pgFoundry are working to make it easier. -- ---(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] query rewrite using materialized views
Wagner, If there is anyone that can give me some tweak parameters or design help on this, it would be ridiculously appreciated. I have already created this in Oracle and it works, but we don't want to have to pay the monster if something as wonderful as Postgres can handle it. In addition to Rod's advice, please increase your checkpoint_segments and checkpoint_timeout parameters and make sure that the pg_xlog is on a seperate disk resource from the database. -- --Josh Josh Berkus Aglio Database Solutions San Francisco ---(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] query rewrite using materialized views
Rod, I do this, PG gets forked many times, it is tough to find the max number of times I can do this, but I have a Proc::Queue Manager Perl driver that handles all of the copy calls. I have a quad CPU machine. Each COPY only hits ones CPU for like 2.1% but anything over about 5 kicks the load avg up. Ill get some explain analysis and table structures out there pronto. -Original Message- From: Rod Taylor [mailto:[EMAIL PROTECTED] Sent: Tuesday, January 04, 2005 1:02 PM To: Wager, Ryan D [NTK] Cc: Postgresql Performance Subject: Re: [PERFORM] query rewrite using materialized views 1)the 250 million records are currently whipped and reinserted as a daily snapshot and the fastest way I have found COPY to do this from a file is no where near fast enough to do this. SQL*Loader from Oracle does some things that I need, ie Direct Path to the db files access (skipping the RDBMS), inherently ignoring indexing rules and saving a ton of time (Dropping the index, COPY'ing 250 million records, then Recreating the index just takes way too long). If you have the hardware for it, instead of doing 1 copy, do 1 copy command per CPU (until your IO is maxed out anyway) and divide the work amongst them. I can push through 100MB/sec using methods like this -- which makes loading 100GB of data much faster. Ditto for indexes. Don't create a single index on one CPU and wait -- send off one index creation command per CPU. 2)Finding a way to keep this many records in a fashion that can be easily queried. I even tried breaking it up into almost 2800 separate tables, basically views of the data pre-broken down, if this is a working method it can be done this way, but when I tried it, VACUUM, and the COPY's all seemed to slow down extremely. Can you send us EXPLAIN ANALYSE output for the slow selects and a little insight into what your doing? A basic table structure, and indexes involved would be handy. You may change column and table names if you like. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Josh Berkus Sent: Tuesday, January 04, 2005 12:06 PM To: pgsql-performance@postgresql.org Cc: Yann Michel Subject: Re: [PERFORM] query rewrite using materialized views Yann, are there any plans for rewriting queries to preexisting materialized views? I mean, rewrite a query (within the optimizer) to use a materialized view instead of the originating table? Automatically, and by default, no. Using the RULES system? Yes, you can already do this and the folks on the MattView project on pgFoundry are working to make it easier. -- ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
Re: [PERFORM] Very Bad Performance.
Martha Stewart called it a Good Thing when [EMAIL PROTECTED] (Pallav Kalva) wrote: Then you have to look at individual slow queries to determine why they are slow, fortunately you are running 7.4 so you can set log_min_duration to some number like 1000ms and then try to analyze why those queries are slow. I had that already set on my database , and when i look at the log for all the problem queries, most of the queries are slow from one of the table. when i look at the stats on that table they are really wrong, not sure how to fix them. i run vacuumdb and analyze daily. Well, it's at least good news to be able to focus attention on one table, rather than being unfocused. If the problem is that stats on one table are bad, then the next question is Why is that? A sensible answer might be that the table is fairly large, but has some fields (that are relevant to indexing) that have a small number of values where some are real common and others aren't. For instance, you might have a customer/supplier ID where there are maybe a few hundred unique values, but where the table is dominated by a handful of them. The default in PostgreSQL is to collect a histogram of statistics based on having 10 bins, filling them using 300 samples. If you have a pretty skewed distribution on some of the fields, that won't be good enough. I would suggest looking for columns where things are likely to be skewed (customer/supplier IDs are really good candidates for this), and bump them up to collect more stats. Thus, something like: alter table my_table alter column something_id set statistics 100; Then ANALYZE MY_TABLE, which will collect 100 bins worth of stats for the 'offending' column, based on 3000 sampled records, and see if that helps. Also hyperthreading may not be helping you.. does it do any harm to the system if it is hyperthreaded ? Yes. If you have multiple hyperthreads running on one CPU, that'll wind up causing extra memory contention of one sort or another. -- let name=cbbrowne and tld=linuxfinances.info in name ^ @ ^ tld;; http://www.ntlug.org/~cbbrowne/sgml.html People who don't use computers are more sociable, reasonable, and ... less twisted -- Arthur Norman ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
Re: [PERFORM] query rewrite using materialized views
Ryan, I do this, PG gets forked many times, it is tough to find the max number of times I can do this, but I have a Proc::Queue Manager Perl driver that handles all of the copy calls. I have a quad CPU machine. Each COPY only hits ones CPU for like 2.1% but anything over about 5 kicks the load avg up. That's consistent with Xeon problems we've seen elsewhere. Keep the # of processes at or below the # of processors. Moving pg_xlog is accomplished through: 1) in 8.0, changes to postgresql.conf (in 8.0 you'd also want to explore using multiple arrays with tablespaces to make things even faster) 2) in other versions: a) mount a seperate disk on PGDATA/pg_xlog, or b) symlink PGDATA/pg_xlog to another location -- --Josh Josh Berkus Aglio Database Solutions San Francisco ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
Re: [PERFORM] query rewrite using materialized views
On Tue, 2005-01-04 at 14:02 -0500, Rod Taylor wrote: 1)the 250 million records are currently whipped and reinserted as a daily snapshot and the fastest way I have found COPY to do this from a file is no where near fast enough to do this. SQL*Loader from Oracle does some things that I need, ie Direct Path to the db files access (skipping the RDBMS), inherently ignoring indexing rules and saving a ton of time (Dropping the index, COPY'ing 250 million records, then Recreating the index just takes way too long). If you have the hardware for it, instead of doing 1 copy, do 1 copy command per CPU (until your IO is maxed out anyway) and divide the work amongst them. I can push through 100MB/sec using methods like this -- which makes loading 100GB of data much faster. Ditto for indexes. Don't create a single index on one CPU and wait -- send off one index creation command per CPU. Not sure what you mean by whipped. If you mean select and re-insert then perhaps using a pipe would produce better performance, since no disk access for the data file would be involved. In 8.0 COPY and CREATE INDEX is optimised to not use WAL at all if archive_command is not set. 8 is great... 2)Finding a way to keep this many records in a fashion that can be easily queried. I even tried breaking it up into almost 2800 separate tables, basically views of the data pre-broken down, if this is a working method it can be done this way, but when I tried it, VACUUM, and the COPY's all seemed to slow down extremely. Can you send us EXPLAIN ANALYSE output for the slow selects and a little insight into what your doing? A basic table structure, and indexes involved would be handy. You may change column and table names if you like. There's a known issue using UNION ALL views in 8.0 that makes them slightly more inefficient than using a single table. Perhaps that would explain your results. There shouldn't be any need to do the 2800 table approach in this instance. -- Best Regards, Simon Riggs ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
Re: [PERFORM] Low Performance for big hospital server ..
I will put more ram but someone said RH 9.0 had poor recognition on the Ram above 4 Gb? I think they were refering to 32 bit architectures, not distributions as such. Sorry for wrong reason , then should I increase more RAM than 4 Gb. on 32 bit Arche.? Should I close the hyperthreading ? Would it make any differnce between open and close the hyperthreading? Thanks for any comment In my experience, the largest performance increases come from intensive analysis and optimisation of queries. Look at the output of EXPLAIN ANALYZE for the queries your application is generating and see if they can be tuned in anyway. More often than not, they can. So what you mean is that the result is the same whether close or open hyperthreading ? Will it be any harm if I open it ? The main point shiuld be adjustment the query , right. Feel free to ask for assistence on irc at irc.freenode.net #postgresql. People there help optimise queries all day ;-). How could I contact with those people ;= which url ? Thanks again. Amrit Thailand ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
