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Re: migrating oracle to postgres

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On Thu, 23 Jun 2011 17:48:09 +0200, Robert Klemme wrote:

> Why do you consider this bad?  I agree that it sounds silly at first
> sight that the user needs to take care of cleaning up deadwood in the
> database.  On the other hand, on an Oracle instance you'll likely also
> have periodic jobs doing statistics updates which is what VACUUMing also
> does.  Reducing the work a transaction has to do can be beneficial for
> the client, too.

No, what I consider bad is the architecture of putting dead rows in the 
table. That prevents Postgres from assigning a fixed row id to every row 
and from creating global indexes on partitioned tables. I believe that 
they should consider putting previous versions of the row in a separate 
table and have the vacuum process, let's call it "smon" for the sake of 
argument, do a periodical cleanup. That way rows in the table are not a 
moving target, there is a possibility of assigning a permanent row id, 
which would also allow creating global indexes.

> 
>> The third is the fact that Postgres doesn't do multi-block reads.
> 
> Isn't this alleviated by the OS doing readahead on many platforms?

Weeellllll....it is. You are right, my objection is mostly of aesthetic 
nature. When I come to think of it, it does simplify the optimizer 
because there is only one type of I/O to think about.



> 
>> Fixed size archive logs (16M) would be the next issue.
> 
> This can be changed during compilation though.  But I agree, you'd
> rather want this to be tuneable at runtime - at least without
> recompiling the software.
> 
>> The lack of shared pool makes it impossible to see the plan of the
>> statement being executed. And there is more.
> 
> That's unfortunate.  At least you can see SQL currently executed by
> querying pg_stat_activity.
> 
> Kind regards

Oh yes, and there is also auto explain module which will dump the plan of 
any statement running longer than a predefined period of time (tunable). 
What I really miss is the ability to click on the session in PgAdmin3 and 
see the plan of a running statement. Also, sorting by the CPU time or the 
number of I/O requests issued would be nice.





-- 
http://mgogala.byethost5.com

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migrating oracle to postgres Username <user@domain.tld> - 2011-06-20 19:28 +0200
  Re: migrating oracle to postgres Mladen Gogala <no@email.here.invalid> - 2011-06-20 20:08 +0000
    Re: migrating oracle to postgres Username <user@domain.tld> - 2011-06-20 23:45 +0200
      Re: migrating oracle to postgres Mladen Gogala <no@email.here.invalid> - 2011-06-20 22:37 +0000
      Re: migrating oracle to postgres Mladen Gogala <gogala.mladen@gmail.com> - 2011-06-21 02:01 +0000
  Re: migrating oracle to postgres "Laurenz Albe" <invite@spam.to.invalid> - 2011-06-21 09:18 +0200
    Re: migrating oracle to postgres Mladen Gogala <gogala.mladen@gmail.com> - 2011-06-21 13:38 +0000
      Is PostgreSQL good? (was: migrating oracle to postgres) "Laurenz Albe" <invite@spam.to.invalid> - 2011-06-22 12:30 +0200
        Re: Is PostgreSQL good? Harry Tuttle <OTPXDAJCSJVU@spammotel.com> - 2011-06-22 13:15 +0200
        Re: Is PostgreSQL good? (was: migrating oracle to postgres) Mladen Gogala <gogala.mladen@gmail.com> - 2011-06-22 12:02 +0000
          Re: Is PostgreSQL good? "M. Strobel" <sorry_no_mail_here@nowhere.dee> - 2011-06-22 21:52 +0200
            Re: Is PostgreSQL good? Mladen Gogala <no@email.here.invalid> - 2011-06-22 22:43 +0000
          Re: Is PostgreSQL good? (was: migrating oracle to postgres) "Laurenz Albe" <invite@spam.to.invalid> - 2011-06-24 12:29 +0200
            Re: Is PostgreSQL good? Hans Castorp <REWYRLXHEGHO@spammotel.com> - 2011-06-24 12:57 +0200
              Re: Is PostgreSQL good? "Laurenz Albe" <invite@spam.to.invalid> - 2011-06-24 14:53 +0200
              Re: Is PostgreSQL good? Mladen Gogala <no@email.here.invalid> - 2011-06-24 16:32 +0000
            Re: Is PostgreSQL good? (was: migrating oracle to postgres) Mladen Gogala <gogala.mladen@gmail.com> - 2011-06-24 13:53 +0000
              Re: Is PostgreSQL good? (was: migrating oracle to postgres) "Laurenz Albe" <invite@spam.to.invalid> - 2011-06-27 11:17 +0200
                Re: Is PostgreSQL good? (was: migrating oracle to postgres) Mladen Gogala <gogala.mladen@gmail.com> - 2011-06-28 06:11 +0000
                Re: Is PostgreSQL good? "Laurenz Albe" <invite@spam.to.invalid> - 2011-06-28 10:34 +0200
                Re: Is PostgreSQL good? Mladen Gogala <gogala.mladen@gmail.com> - 2011-06-28 13:30 +0000
                Re: Is PostgreSQL good? "Laurenz Albe" <invite@spam.to.invalid> - 2011-06-29 09:50 +0200
                Re: Is PostgreSQL good? Mladen Gogala <no@email.here.invalid> - 2011-06-29 21:38 +0000
                Re: Is PostgreSQL good? "Laurenz Albe" <invite@spam.to.invalid> - 2011-06-30 09:14 +0200
                Re: Is PostgreSQL good? Mladen Gogala <mgogala@no.address.invalid> - 2011-06-30 13:22 +0000
            Re: Is PostgreSQL good? Don Y <nowhere@here.com> - 2011-06-30 07:05 -0700
              Re: Is PostgreSQL good? Mladen Gogala <no@email.here.invalid> - 2011-06-30 15:41 +0000
                Re: Is PostgreSQL good? Richard Kettlewell <rjk@greenend.org.uk> - 2011-06-30 16:49 +0100
                Re: Is PostgreSQL good? Mladen Gogala <no@email.here.invalid> - 2011-06-30 19:24 +0000
                Re: Is PostgreSQL good? Don Y <nowhere@here.com> - 2011-06-30 13:21 -0700
                Re: Is PostgreSQL good? Mladen Gogala <no@email.here.invalid> - 2011-06-30 22:42 +0000
                Re: Is PostgreSQL good? Don Y <nowhere@here.com> - 2011-07-01 11:57 -0700
                Re: Is PostgreSQL good? Mladen Gogala <gogala.mladen@gmail.com> - 2011-07-01 22:58 +0000
                Re: Is PostgreSQL good? Richard Kettlewell <rjk@greenend.org.uk> - 2011-07-01 14:07 +0100
                Re: Is PostgreSQL good? Mladen Gogala <gogala.mladen@gmail.com> - 2011-07-01 13:29 +0000
                Re: Is PostgreSQL good? Don Y <nowhere@here.com> - 2011-06-30 13:17 -0700
                Re: Is PostgreSQL good? Mladen Gogala <gogala.mladen@gmail.com> - 2011-06-30 23:53 +0000
              Re: Is PostgreSQL good? "Laurenz Albe" <invite@spam.to.invalid> - 2011-07-01 10:13 +0200
                Re: Is PostgreSQL good? Mladen Gogala <gogala.mladen@gmail.com> - 2011-07-01 13:38 +0000
                Re: Is PostgreSQL good? "Laurenz Albe" <invite@spam.to.invalid> - 2011-07-01 16:58 +0200
                Re: Is PostgreSQL good? Mladen Gogala <no@email.here.invalid> - 2011-07-01 15:33 +0000
                Re: Is PostgreSQL good? Don Y <nowhere@here.com> - 2011-07-01 11:39 -0700
                Re: Is PostgreSQL good? "Laurenz Albe" <invite@spam.to.invalid> - 2011-07-04 16:39 +0200
                Re: Is PostgreSQL good? Don Y <nowhere@here.com> - 2011-07-04 12:11 -0700
                Re: Is PostgreSQL good? "Laurenz Albe" <invite@spam.to.invalid> - 2011-07-05 08:58 +0200
                Re: Is PostgreSQL good? Don Y <nowhere@here.com> - 2011-07-05 11:29 -0700
                Re: Is PostgreSQL good? "Laurenz Albe" <invite@spam.to.invalid> - 2011-07-06 09:00 +0200
                Re: Is PostgreSQL good? Don Y <nowhere@here.com> - 2011-07-06 01:00 -0700
                Re: Is PostgreSQL good? "Laurenz Albe" <invite@spam.to.invalid> - 2011-07-07 09:05 +0200
                Re: Is PostgreSQL good? Don Y <nowhere@here.com> - 2011-07-07 00:34 -0700
                Re: Is PostgreSQL good? Matthew Woodcraft <mattheww@chiark.greenend.org.uk> - 2011-07-04 20:12 +0100
                Re: Is PostgreSQL good? Don Y <nowhere@here.com> - 2011-07-04 12:24 -0700
      Re: migrating oracle to postgres Robert Klemme <shortcutter@googlemail.com> - 2011-06-23 17:48 +0200
        Re: migrating oracle to postgres Mladen Gogala <no@email.here.invalid> - 2011-06-23 16:42 +0000
          Re: migrating oracle to postgres Mladen Gogala <no@email.here.invalid> - 2011-06-23 18:57 +0000
          Re: migrating oracle to postgres Robert Klemme <shortcutter@googlemail.com> - 2011-06-26 17:35 +0200
            Re: migrating oracle to postgres Mladen Gogala <gogala.mladen@gmail.com> - 2011-06-26 19:08 +0000
          Re: migrating oracle to postgres Robert Klemme <shortcutter@googlemail.com> - 2011-06-27 00:32 -0700
            Re: migrating oracle to postgres Mladen Gogala <no@email.here.invalid> - 2011-06-28 16:00 +0000
              Re: migrating oracle to postgres Robert Klemme <shortcutter@googlemail.com> - 2011-06-28 22:28 +0200

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