Re: [PERFORM] Concurrency issue under very heay loads

2009-07-17 Thread Haszlakiewicz, Eric
>-Original Message- >From: pgsql-performance-ow...@postgresql.org > >We use a typical counter within a transaction to generate >order sequence number and update the next sequence number. >This is a simple next counter - nothing fancy about it. When >multiple clients are concurrently a

Re: [PERFORM] Calling conventions

2009-07-17 Thread Kevin Grittner
Matthew Wakeling wrote: > I have implemented the very same algorithm in both a Postgres GiST > extension and as a standalone Java program. In general, the > standalone Java program performs about 100 times faster than > Postgres when running a large index-based nested loop join. > > I profiled

Re: [PERFORM] Calling conventions

2009-07-17 Thread Tom Lane
Peter Eisentraut writes: >> Does anyone have any ideas/opinions/statistics on what the performance >> difference is between the two calling conventions? > Version 1 is technically slower if you count the number of instructions, That would be true if you compare version-0-to-version-0 calls (ie,

Re: [PERFORM] Calling conventions

2009-07-17 Thread Matthew Wakeling
On Fri, 17 Jul 2009, Peter Eisentraut wrote: On Friday 17 July 2009 16:40:40 Matthew Wakeling wrote: I'm considering rewriting a postgres extension (GiST index bioseg) to make it use version 1 calling conventions rather than version 0. Does anyone have any ideas/opinions/statistics on what the

Re: [PERFORM] Calling conventions

2009-07-17 Thread Peter Eisentraut
On Friday 17 July 2009 16:40:40 Matthew Wakeling wrote: > I'm considering rewriting a postgres extension (GiST index bioseg) to make > it use version 1 calling conventions rather than version 0. > > Does anyone have any ideas/opinions/statistics on what the performance > difference is between the t

Re: [PERFORM] cluster index on a table

2009-07-17 Thread Kevin Grittner
Scara Maccai wrote: >> Be sure to include an ORDER BY clause. > Isn't it going to be much slower? It might be; you'd have to test to know for sure. > The important thing is that most of the records are stored "close" > enough one to the other in the right order. Then, yeah, it might not

Re: [PERFORM] cluster index on a table

2009-07-17 Thread Scara Maccai
> Be sure to include an ORDER BY clause.  For > example, if someone else starts a query which the planner > determines > is best handled with a table scan, and that is still > running when you > issue your INSERT/SELECT, your query will join the current > scan at > it's point of progress, and "wra

Re: [PERFORM] Concurrency issue under very heay loads

2009-07-17 Thread Craig Ringer
On Thu, 2009-07-16 at 00:11 -0600, Scott Marlowe wrote: > As others have said, a serial is a good idea, HOWEVER, if you can't > have gaps in sequences, or each customer needs their own sequence, > then you get to lock the rows / table / etc that you're mucking with > to make sure you don't issue t

Re: [PERFORM] cluster index on a table

2009-07-17 Thread Kevin Grittner
Scara Maccai wrote: > - create table mytable as select * from where time > (this gets all the data of last month ordered in the > "almost" correct order, because all the single tables were > clustered) Be sure to include an ORDER BY clause. Without that, there is no guarantee that even two

[PERFORM] Calling conventions

2009-07-17 Thread Matthew Wakeling
I'm considering rewriting a postgres extension (GiST index bioseg) to make it use version 1 calling conventions rather than version 0. Does anyone have any ideas/opinions/statistics on what the performance difference is between the two calling conventions? Matthew -- Patron: "I am looking

Re: [PERFORM] cluster index on a table

2009-07-17 Thread ph...@apra.asso.fr
Hi all, >On Wed, Jul 15, 2009 at 10:36 PM, Scott Marlowe >wrote: I'd love to see it. > > +1 for index organized tables > >--Scott +1 also for me... I am currently working for a large customer who is migrating his main application towards PostgreSQL, this application currently using DB2 an

Re: [PERFORM] Strange memory behavior with rails - caching in connection?

2009-07-17 Thread Scott Marlowe
On Wed, Jul 15, 2009 at 2:44 AM, Alex wrote: > I am using Postgres with Rails.  Each rails application "thread" is > actually a separate process (mongrel) with it's own connection. > > Normally, the db connection processes (?) look something like this in > top: > > 15772 postgres  15   0  229m  13m

Re: [PERFORM] cluster index on a table

2009-07-17 Thread Scara Maccai
> As Kevin said, there's no guarantee that tuples will be > read back > in the order you inserted them. Ok, didn't know that > A better option you might consider is to use a separate > table for the > re-ordered tuples. > You could even do this using partitions Problem is I'm already using par