Thread: a few questions
I have a few questions:
1. what is pg_xlog
someone told me that i can move pg_xlog to a different parttion in order to boost the performance? Does it work and how
2. there is a parameter in postgresql.conf called max_connections. which is 100 be default. i want o decrease it to 20.
by doing this how much can i increase the value of shared buffers?
by default it is 1000, how much can i increase to in order to boost up the performance
3. What other things can i do to boost up the performance assuming that the stored procedures are well optimized.
4. I recently tried to start postmaster. But it simply timed out. i tried to find out if there is any postmaster process running, but it was not running.
my question is that can u decrease this timeout, right now i think it takes some 1 or 2 minutes...
5. i have also seen multiple instances of postmaster.
in my script ot start postmaster i first check if it is running by doing pidof, and only if it is nor running i start it
still have seen multiple instances.
how did that happen? also if i stop postmaster, only one instance is stopped.
is there any command to stop all instances of postmaster
6. what does ipcclean do? how do i know what shared memory was used by postmaster so that i can clear it, before starting postmaster
7. some times if i do a dropdb abc(assuming abc is a database)
it displays a message can not remove directory 12345, although the database is dropped, what shuld be done in such a case?
thanks,
regards
Surabhi
On Thu, Dec 29, 2005 at 03:09:52PM +0530, surabhi.ahuja wrote: > I have a few questions: > 1. what is pg_xlog > someone told me that i can move pg_xlog to a different parttion in order to boost the performance? Does it work and how Yes, it works. How? By moving the directory (while the postmaster is not running) and creating a symlink in the right place. > 2. there is a parameter in postgresql.conf called max_connections. which is 100 be default. i want o decrease it to 20. > by doing this how much can i increase the value of shared buffers? > by default it is 1000, how much can i increase to in order to boost up the performance They have nothing to do with eachother. Depending on how much memory you have, the shared_buffers could be increased by a factor of 10. Max connections won't change anything there. > 3. What other things can i do to boost up the performance assuming that the stored procedures are well optimized. Google the web, or try the pgsql-performence mailing list. > 4. I recently tried to start postmaster. But it simply timed out. i tried to find out if there is any postmaster processrunning, but it was not running. > my question is that can u decrease this timeout, right now i think it takes some 1 or 2 minutes... Look in the logs for an error message. > 5. i have also seen multiple instances of postmaster. > in my script ot start postmaster i first check if it is running by doing pidof, and only if it is nor running i start it > still have seen multiple instances. > how did that happen? also if i stop postmaster, only one instance is stopped. Each connection appears as a new process, so pidof wont't work. You need to use the pidfile the postmaster creates. Why arn't you using one of the startup scripts provided? > is there any command to stop all instances of postmaster Are you sure you have more than one? > 6. what does ipcclean do? how do i know what shared memory was used by postmaster so that i can clear it, before startingpostmaster PostgreSQL takes care of it's own ipc memory, you should never need to use ipcclean ever. > 7. some times if i do a dropdb abc(assuming abc is a database) > it displays a message can not remove directory 12345, although the database is dropped, what shuld be done in such a case? Please provide the exact error message. Oh, and while you're at it, what platform and what version of postgres. Without that info it's impossible to give any real help, Have a nice day, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a > tool for doing 5% of the work and then sitting around waiting for someone > else to do the other 95% so you can sue them.
Attachment
On Thu, Dec 29, 2005 at 03:40:11PM +0530, surabhi.ahuja wrote: > pidof of doesnt work ? Given the number of processes is going to be at least 3+number of connections, how is pidof going to know which one you mean? Answer: it doesn't, so you end up killing a random one. > which startup script are u reffering to? In recent releases they're under contrib/start-scripts but they've been there for a while. Since you didn't say which version, I can't help you more than that. Have a nice day, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a > tool for doing 5% of the work and then sitting around waiting for someone > else to do the other 95% so you can sue them.
Attachment
On Fri, Dec 30, 2005 at 06:21:28PM +0530, surabhi.ahuja wrote: > I am working with PostgerSQL 8.0.0. > where can i find the startup scripts for the same. Well, it's been in contrib/strat-scripts since 8.0.0 so you should find it there. > One more thing, > I could not understand this: > number of processes is going to be at least 3+number of connections > > do u mean that for each connection there is a "postmaster" process? and what are those 3 processes? > actually the ppl who use the application often use kill -9 postmaster. in such a case the pid file still remains. One postmaster, 2 for the stats collector and possibly 1 for the autovacuum daemon. Plus one for each connection to the database. People shouldn't use kill -9 on the postmaster, they should use the normal signals, or just "pg_ctl stop". Or if you use a startup script, /etc/init.d/postgresql start/stop. Have a nice day, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a > tool for doing 5% of the work and then sitting around waiting for someone > else to do the other 95% so you can sue them.